Advances in Algae-Based Bioplastics: From Strain Engineering and Fermentation to Commercialization and Sustainability

Abstract

The development of algal bioplastics offers a promising pathway toward sustainable materials that can mitigate reliance on fossil fuel-derived plastics. This article reviews recent advances in algal cultivation, strain optimization, biopolymer extraction, and processing technologies, alongside techno-economic and life cycle assessments. Special emphasis is placed on integrated biorefinery models, innovative processing techniques, and the role of government–industry–academia partnerships in accelerating commercialization. The analysis incorporates both demonstrated algal systems and theoretical applications derived from established microbial processes, reflecting the emerging nature of this field. The environmental advantages, market readiness, and scalability challenges of algal bioplastics are critically evaluated, with reference to peer-reviewed studies and industrial pilot projects. The analysis underscores that while technical feasibility has been demonstrated, economic viability and large-scale adoption depend on optimizing yield, reducing production costs, and fostering collaborative frameworks. Future research priorities include enhancing strain performance via AI-enabled screening, expanding product valorization streams, and aligning regulatory standards to support global market integration.

1. Introduction

1.1. Plastic Pollution and the Rise in Bioplastics

Plastic pollution is a critical global environmental issue, with millions of tons of mismanaged plastics entering marine ecosystems annually, causing long-term harm to biodiversity, ecosystem health, and human well-being [1,2]. Conventional petrochemical-based plastics can persist for centuries, making their accumulation a persistent ecological threat.

In response, bioplastics—polymers derived from renewable biological sources and/or designed for biodegradation—have gained market momentum [3]. Growth is driven by policy interventions and consumer demand, with polylactic acid (PLA) emerging as one of the most commercially viable options [4].

Bioplastics can reduce environmental impact and, under optimal conditions, degrade into benign by-products [5]. However, real-world performance is limited by disposal conditions and waste management infrastructure [6,7]. Packaging remains the dominant application, yet challenges such as insufficient composting infrastructure, low consumer awareness, and recycling contamination hinder wider adoption [6]. Aligning technological innovation with effective policy, public engagement, and robust life cycle assessment is essential to realizing their sustainability potential [8].

However, significant challenges persist. Algal cultivation requires 10–30 kWh/kg dry biomass for mixing and temperature control, substantially higher than terrestrial crops [9]. Seasonal productivity can vary 1.5–3 fold in temperate regions, and contamination risks increase at scale [10]. These factors currently result in production costs 2–4 times higher than conventional plastics [11].

1.2. Limitations of Starch and Corn-Based Bioplastics

First-generation starch- and corn-based bioplastics are notable for their biodegradability and renewable origins but face persistent material and sustainability challenges. Their high hygroscopicity leads to excessive water absorption, causing dimensional instability and mechanical deterioration in humid conditions [12,13]. They also tend to have lower tensile strength and elasticity compared to conventional plastics, with crystalline structures—such as A-type starch in corn—limiting processing and durability [14]. Although additive reinforcement can enhance performance, improvements remain modest [15].

Their production also depends on resource-intensive agriculture, competing with food crops for land, water, and energy, and raising ethical and environmental concerns under conditions of growing global demand [16]. These limitations underscore the need for alternative feedstocks that avoid trade-offs between material performance, resource efficiency, and food security [17].

1.3. Algae as a Carbon-Neutral, Fast-Growing, Nutrient-Rich Feedstock

Algae offer a promising next-generation feedstock for bioplastics due to their rapid growth, capacity to thrive on non-arable land using non-potable water, and potential for carbon-neutral production, with some species sequestering substantial amounts of CO₂ per unit biomass [18,19]. Compared with terrestrial crops, algae require fewer agricultural inputs and exhibit higher areal productivity. Certain microalgal strains accumulate substantial carbohydrate or lipid content suitable for bioplastic production. For instance, Botryococcus braunii can accumulate lipids up to 75% of dry weight [20,21], while Porphyridium cruentum produces polysaccharides up to 40–55% of biomass [22,23]. Meanwhile, cyanobacterial strains such as Synechocystis sp. PCC 6803 and Nostoc sp. have been engineered to produce polyhydroxyalkanoates directly [24].

Beyond primary polymer production, algae can serve as reinforcing agents in hybrid composites, enhancing thermal and mechanical properties, and integrate well into biorefinery systems where residual biomass is converted into co-products such as fertilizers, animal feed, or bioenergy [25]. Cultivation in nutrient-rich wastewater or agricultural runoff further strengthens sustainability credentials by closing material loops [26]. This versatility positions algae as a renewable, multifunctional resource aligned with circular economy principles [27].

1.4. Scope and Novelty of the Review

While prior reviews have examined aspects of algal biotechnology and bioplastic production, most address only isolated segments—either upstream cultivation or downstream processing—without integrating the entire value chain. Few have linked metabolic engineering, multiple fermentation routes, advanced material blends, and techno-economic assessments into a single analytical framework [28,29,30,31].

This review adopts a comprehensive approach by classifying and critically comparing key fermentative strategies (heterotrophic, dark, and engineered algal systems), benchmarking material properties and environmental performance, and examining industrial case studies alongside emerging tools such as CRISPR/Cas9, riboswitches, and AI-assisted strain optimization. By bridging academic advances with commercial developments, it identifies both the opportunities and the scientific, technical, and socio-economic gaps that must be addressed for large-scale, sustainable deployment of algae-based bioplastics.

2. Methodology

2.1. Literature Search Strategy

A systematic literature search was conducted between September 2024 and January 2025 using Web of Science, Scopus, PubMed, Google Scholar, and ScienceDirect. The search string used was: ((“algae” OR “microalgae” OR “macroalgae” OR “cyanobacteria” OR “seaweed”) AND (“bioplastic*” OR “PHA” OR “polyhydroxyalkanoate” OR “PLA” OR “polylactic acid” OR “nanocellulose”) AND (“fermentation” OR “extraction” OR “biorefinery” OR “strain engineering” OR “genetic modification”)). Inclusion criteria: (1) peer-reviewed articles published 2018–2025, (2) studies reporting quantitative data on algal biomass or bioplastic production, (3) English language. Exclusion criteria: (1) conference abstracts without full text, (2) studies without primary data, (3) duplicate publications. Initial search yielded more than 1800 articles. After title/abstract screening, a little more than 600 remained. Full-text review resulted in around 300 articles included in final analysis. Boolean operators combined algae-related terms (“algae,” “microalgae,” “macroalgae,” “cyanobacteria,” “seaweed”) with bioplastic terminology (“bioplastic*,” “PHA,” “PLA,” “nanocellulose”) and production process terms (“fermentation,” “extraction,” “biorefinery”). The search also encompassed patent databases (USPTO, EPO, WIPO) to capture recent commercial developments. Monthly updates were performed during the preparation period to incorporate emerging studies in this rapidly evolving field. A PRISMA flow diagram of the systematic literature search strategy has been shown in Figure 1.

2.2. Data Extraction and Classification

A standardized extraction protocol recorded algae species, bioplastic type, production method, yields, mechanical properties, economic indicators, and environmental performance metrics. For parameters reported across multiple studies, ranges and median values were calculated to account for variability. Technologies were classified by:

• Bioplastic type: PHA, PLA, nanocellulose, or blended composites.
• Production pathway: direct synthesis, fermentation, or chemical conversion.
• Scale: laboratory, pilot, or commercial.

2.3. Comparative Analysis

Comparative evaluation used standardized indicators, including:

• Production cost (USD/kg).
• Greenhouse gas emissions (kg CO₂-eq/kg).
• Water consumption (L/kg).
• Biodegradation rate (% mass loss over a defined period).

2.4. Technology Readiness Level (TRL) Assessment

Technology readiness levels (TRL 1–9) were assigned to assess commercial maturity, with TRL 1 indicating basic principle observation and TRL 9 representing fully operational deployment. Research gaps were identified by mapping current literature against industrial requirements and examining barriers to technology transfer.

TRL values were assigned following the NASA/DoD 1–9 scale, using literature-reported levels where available [32]. TRL assignments followed the NASA/DoD framework with specific criteria: TRL 1–3: Laboratory proof-of-concept (bench scale < 1 L); TRL 4–5: Laboratory validation (1–10 L scale); TRL 6–7: Pilot scale demonstration (>10 L, outdoor cultivation for algae); TRL 8–9: Commercial deployment (>1000 L, market products) [32]. When not explicitly stated, TRL was assigned based on: reported scale (L or m²), indoor/outdoor cultivation, presence of techno-economic analysis, and commercial partnerships mentioned. For methods without explicit TRL data, values were inferred from reported demonstration scale (lab, pilot, or industrial), reproducibility across studies, and evidence of commercial or analogous bioprocess use. These estimates are indicative of maturity at the time of review and support comparative discussion rather than definitive certification.

2.5. Quality Assurance and Limitations

Data accuracy was verified through cross-referencing with recent reviews (2022–2024) and managing references using citation software (Endnote 2025) to avoid duplication. Limitations of this review include potential language bias from the English-only search, publication bias toward positive findings, and restricted access to proprietary industrial data. Given the nascent stage of algal bioplastic technology, peer-reviewed literature specifically addressing algal systems remains limited compared to bacterial production systems. Where direct algal production data was unavailable, comparative analysis with established microbial systems was included with appropriate contextualization.

2.6. Scope Clarification

Due to the emerging nature of algal bioplastic production, this review includes both demonstrated algal production systems and theoretical applications based on algal biomass composition and established fermentation processes. Where algal-specific data is limited, the review draws parallels from bacterial and other microbial systems to identify potential pathways and benchmarks for algal development. Such instances are clearly indicated to maintain transparency about the current state of technology.

3. Types of Algal Bioplastics

The production of algal bioplastics involves multiple interconnected stages, each presenting opportunities for optimization and integration within a biorefinery framework (Figure 2). Understanding this complete value chain is essential for identifying technical bottlenecks, economic drivers, and sustainability impacts throughout the production pathway.

The process flow illustrates key stages including: (1) algal cultivation using various nutrient sources, (2) biomass harvesting and dewatering, (3) cell disruption and component extraction, (4) bioplastic synthesis via fermentation or direct processing, (5) polymer purification and recovery, (6) product formulation and manufacturing, and (7) end-of-life options including composting, marine degradation, and recycling. Dashed lines indicate potential material/energy recovery loops for circular economy integration. Major decision points and process alternatives are shown at each stage.

3.1. Polyhydroxyalkanoates (PHAs)

Polyhydroxyalkanoates (PHAs) are a class of biodegradable polyesters synthesized by microorganisms, including bacteria and cyanobacteria, under nutrient-limited conditions [33,34,35]. Their biodegradability, biocompatibility, and tunable mechanical properties make them credible alternatives to petroleum-based plastics [36]. Variations in monomer composition—such as the ratio of hydroxybutyrate to hydroxyvalerate—allow tailoring of brittleness, flexibility, and thermal stability for specific applications.

3.1.1. Direct PHA Production in Algal and Cyanobacterial Systems

Cyanobacteria accumulate polyhydroxyalkanoates (PHAs), mainly poly-β-hydroxybutyrate (PHB), as carbon and energy reserves under nitrogen or phosphorus limitation [37,38]. Synechocystis sp. PCC 6803 typically reaches ~4.55% DCW, Nostoc muscorum ~8.6% DCW [38], and Aulosira fertilissima up to 35–38% DCW under optimized conditions [39]. PHB accumulation is strongly induced by carbon/nitrogen starvation [37]. Green algae such as Scenedesmus also produce PHAs but usually <5% DCW, highlighting the superior efficiency of cyanobacteria. Marine strains like Synechococcus sp. and Prochlorococcus sp. can achieve 10–20% DCW and offer the added benefit of seawater cultivation [39].

3.1.2. Algal Biomass as Feedstock for Bacterial PHA Production

A more established approach involves using algal biomass as a carbon feedstock for heterotrophic bacteria. After cell disruption and hydrolysis, algal sugars and lipids serve as substrates for PHA-producing bacteria such as Cupriavidus necator, Bacillus sp., and Pseudomonas sp. This two-stage process typically yields between 3.1 and 18.57 g/L, depending on species, substrate, and fermentation conditions. Reported averages often fall within the 6–10 g/L range, though optimized systems have achieved yields as high as 18.57 g/L [40,41,42]. The use of waste substrates such as agricultural residues in combination with algal biomass reduces feedstock costs while addressing waste management challenges [43].

3.1.3. Genetic Engineering and Future Potential

Genetic engineering of microalgae represents an emerging strategy to enhance PHA production. Chlorella and Chlamydomonas reinhardtii have been transformed with bacterial PHA biosynthetic pathways [44,45], though commercial viability remains limited by low transformation efficiency and genetic instability. Current engineered strains achieve PHA accumulation of 7–15% DCW, significantly below the 50–80% DCW achieved in engineered bacteria. Key challenges include: (1) limited genetic tools for most algal species, (2) metabolic burden of heterologous pathway expression, and (3) competition between PHA synthesis and essential cellular functions.

Despite current limitations, applications for algal-derived PHAs span packaging films and disposable items to medical products such as sutures and drug delivery systems [46,47,48,49]. PHAs degrade within 1.5–3.5 years in ambient conditions [49], with faster breakdown under industrial composting. The main commercial bottlenecks remain high production costs and yield limitations, which may be mitigated through improved metabolic engineering, feedstock diversification, and integration into biorefinery models [50].

3.2. Polylactic Acid (PLA)

Polylactic Acid (PLA) is a biodegradable thermoplastic aliphatic polyester produced via fermentation of sugars to lactic acid, followed by polymerization. The commercial production of PLA predominantly utilizes first-generation feedstocks, such as corn starch and sugarcane, with production volumes that have been estimated to reach at least 800,000 tons annually by 2020 with well-established processing technologies [51,52].

3.2.1. Algal Biomass as Alternative PLA Feedstock

Microalgae present a theoretical alternative carbohydrate source for PLA production, offering cultivation advantages that avoid competition for arable land and freshwater [53,54]. Several microalgal species contain fermentable carbohydrates suitable for lactic acid production: Chlorella vulgaris (12–17% starch content), Scenedesmus obliquus (up to 20% carbohydrate), and Arthrospira platensis (8–14% glycogen) under standard cultivation conditions [55,56]. Under nutrient stress, some species can accumulate carbohydrates up to 40–50% of dry cell weight [57,58].

The conversion pathway from algal biomass to PLA involves: (1) cell disruption and carbohydrate extraction, (2) hydrolysis to fermentable sugars, (3) fermentation to lactic acid using conventional bacteria (Lactobacillus spp.), and (4) polymerization. Current research has demonstrated successful lactic acid production from algal hydrolysates, achieving yields of 0.4–0.6 g lactic acid/g sugar, comparable to agricultural feedstocks [59].

3.2.2. Performance Characteristics and Environmental Considerations

While algae-derived PLA remains at pilot scale, material properties are expected to match conventional PLA (tensile strength 50–65 MPa, elongation at break 6–15%) since the polymerization process and final polymer structure remain unchanged [60]. The distinction lies in the feedstock source rather than the end product characteristics. Composting behavior (60–90 days under industrial conditions) would similarly match conventional PLA [61].

Life cycle assessments project potential GHG emission reductions of 10–30% when replacing corn with algae, primarily due to photosynthetic CO₂ sequestration during cultivation and reduced agricultural inputs [62]. However, these assessments rely on optimized scenarios not yet demonstrated at commercial scale. Current techno-economic analyses indicate production costs 2–3 times higher than corn-based PLA, with cultivation and harvesting representing major cost contributors [63,64].

3.2.3. Research Gaps and Development Priorities

The transition from concept to commercial algae-derived PLA faces several technical barriers:—Improving carbohydrate extraction efficiency from robust algal cell walls—Optimizing enzymatic hydrolysis for diverse algal polysaccharides—Achieving consistent biomass composition despite cultivation variability—Reducing energy requirements for harvesting and processing

Recent advances include development of algal PLA blends incorporating algal nanocellulose as reinforcement [65], and integration with biorefinery concepts for co-product valorization. Applications would mirror conventional PLA markets: rigid and flexible packaging, 3D printing filaments, biomedical devices, and single-use goods [66].

3.3. Algal Nanocellulose

Algal nanocellulose refers to nanoscale cellulose fibers extracted from algal biomass, primarily from green and red algae species such as Cladophora and Gelidium [67,68]. These fibers possess high crystallinity, tensile strength, and excellent barrier properties, making them suitable for advanced material applications [69]. Cellulose content in Cladophora can exceed 20–30% of dry weight, with reported crystallinity contributing to tensile strengths of ~150 MPa in laboratory-produced films [61].

Extraction methodologies—including enzymatic hydrolysis—can improve yield and purity, which are critical for industrial applications [70]. Nanocellulose from algae has been successfully incorporated into PLA and PHA matrices, significantly improving mechanical strength and thermal stability without substantially increasing material density [65].

Applications extend beyond packaging into biomedical domains, such as drug delivery and tissue engineering, owing to the material’s biocompatibility and non-toxicity [71]. However, commercial adoption is hindered by high extraction costs, energy-intensive processing, and challenges in scaling up production [70]. Overcoming these limitations will require innovations in extraction technology and integrated biorefinery approaches that valorize co-products from algal biomass.

3.4. PLA-Based Blends: Comparative Analysis

Blending polylactic acid (PLA) with other polymers, biopolymers, or fillers can improve mechanical performance, thermal stability, and biodegradability, while tailoring materials for specific applications.

Table 1. Comparative Properties of PLA Blends.

PLA Blend	Mechanical Properties *	Thermal Properties *	Biodegradation Rate **	Key Applications	Advantages	Limitations
PLA–PCL	Tensile strength ~150–170 MPa; elongation 100–300% [72,73,74]	Tg: ~55 °C; Tm: ~170 °C (PLA), ~60 °C (PCL) [75]	Moderate; faster than neat PLA in compost/soil [76,77]	Flexible packaging, biomedical scaffolds	High flexibility, good toughness	Lower stiffness, slower biodegradation than other blends
PLA–PBS	Tensile strength ~45–50 MPa; elongation 50–150% [78,79,80]	Tg: ~55 °C; Tm: ~114 °C (PBS) [78,79,80]	Faster than PLA in compost [78,79,80]	Packaging films, agricultural mulch	Balanced strength/flexibility	Limited thermal stability
PLA–PHA	Tensile strength ~40–55 MPa; elongation 10–50% [81,82]	Tg: ~55 °C; Tm: 150–175 °C (PHA) [81,82]	Enhanced biodegradation in marine/soil [83]	Medical devices, food packaging	Good barrier properties	Brittleness at high PLA ratios
PLA–Natural Fibers (e.g., flax, hemp)	Tensile strength 50–70 MPa; elongation 5–15% [84,85]	Tg: ~55 °C; variable Tm [86,87]	Slow in ambient soil, faster in compost [88,89]	Automotive interiors, construction	High stiffness, renewable fillers	Poor impact resistance, moisture sensitivity
PLA–Starch	Tensile strength ~20–40 MPa; elongation 2–10% [90,91,92]	Tg: ~55 °C; Tm ~160 °C [90,91,92]	Rapid in compost/soil [93,94]	Disposable cutlery, packaging	Low cost, high biodegradability	Poor water resistance, reduced strength
PLA–Chitosan	Tensile strength ~30–50 MPa; elongation 2–20% [95,96]	Tg: ~55 °C; variable Tm [95,96]	Rapid in compost and marine [97]	Antimicrobial films, wound dressings	Antimicrobial activity	Limited processability
PLA–Silk Fibroin	Tensile strength ~40–60 MPa; elongation 5–15% [98,99,100,101]	Tg: ~55 °C; Tm ~220 °C (silk) [98,99,100,101]	Moderate in compost [102,103]	Biomedical scaffolds, sutures	High biocompatibility, strength	Higher cost, sourcing constraints
PLA–Graphene Oxide	Tensile strength ~60–75 MPa; elongation 2–10% [104,105]	Tg: ~55 °C; improved thermal stability [106]	Similarly to PLA	Electronics, high-strength films	Improved mechanical/thermal properties	Non-biodegradable filler may reduce compostability

* Properties vary by blend ratio and processing conditions; ranges are representative from literature. ** Biodegradation rates refer to relative trends under standard composting or soil burial.

compares the properties of common PLA blends.

Comparative Analysis

Among these blends, PLA–PCL and PLA–PBS stand out for flexibility, making them suitable for applications where toughness is needed, but they sacrifice stiffness. PLA–PHA offers superior biodegradation in diverse environments, including marine settings, making it promising for applications with high litter risk. PLA–natural fiber composites achieve high stiffness and strength, rivaling some petroleum-based plastics, but moisture uptake can limit performance. PLA–starch is highly biodegradable and inexpensive, yet mechanical performance is compromised. PLA–chitosan provides unique antimicrobial properties but may face scaling challenges. PLA–silk fibroin targets niche biomedical markets where high strength and biocompatibility justify higher costs. PLA–graphene oxide significantly boosts strength and thermal resistance but can hinder biodegradability, raising end-of-life concerns.

The choice of blend should balance mechanical performance, thermal stability, and end-of-life fate, with application-specific priorities guiding material selection. Notably, blends incorporating biodegradable components like PHA, starch, or chitosan align best with circular economy principles, while inorganic or non-biodegradable fillers require careful life cycle planning.

3.5. Challenges and Industrial Potential

Despite significant progress, the large-scale adoption of algal-based bioplastics faces persistent technical, economic, and logistical barriers.

Material compatibility remains one of the most consistent challenges, as blending different polymers and biomass types can lead to phase separation, reduced mechanical strength, and compromised durability [107]. Compatibilizers and plasticizers are often used to mitigate these issues, but they increase production complexity and cost [108].

Processing optimization is equally critical. Techniques such as melt blending and solvent casting must ensure uniform biomass dispersion and strong interfacial bonding to maintain product integrity [109]. Achieving consistent quality across scales—from lab to pilot to industrial—remains a bottleneck for commercialization.

Economic feasibility is influenced by both feedstock and processing costs. Techno-economic assessments reveal that algal biomass production is still more expensive than conventional petrochemical feedstocks [110]. However, integrated biorefinery approaches—where residual biomass is converted into co-products like animal feed, fertilizers, or bioenergy—can improve overall system economics [111,112].

From a market-readiness perspective, certain algal bioplastics such as PHAs and PLA are approaching mid- to high-level Technology Readiness Levels (TRL 6–8), particularly when algae serve as a feedstock in existing fermentation processes. In contrast, emerging materials like algal nanocellulose composites remain at lower TRL stages (TRL 3–5) due to scalability challenges.

Integration with existing petrochemical infrastructure may serve as a transitional model, enabling industries to partially substitute petro-based plastics without overhauling entire manufacturing systems [112]. Furthermore, global regulatory pressure, corporate sustainability targets, and consumer demand for eco-friendly products are creating favorable conditions for adoption [113].

In the long term, advances in metabolic engineering, AI-assisted strain optimization, and precision fermentation could lower costs, increase yields, and expand the performance range of algal bioplastics—positioning them as central components in a circular, bio-based economy. A summary of the descriptions of bioplastics has been tabulated in

Table 2. Comparative Summary of Bioplastics: Types, Properties, Applications, and Commercial Outlook.

Type of Algal Bioplastic	Key Properties	Primary Applications	Commercial Potential
Polyhydroxyalkanoates (PHAs)	Biodegradable (degradation time: 1.5–3.5 years) [49]; tensile strength ~20–50 MPa, elongation at break ~5–600%; average productivity 1.33 g/L·h [114,115,116,117]	Packaging, medical devices such as sutures and drug delivery systems	High production costs but efficiency improves with biotechnological advances; promising feedstocks include agricultural residues.
Polylactic Acid (PLA)	Compostable in ~60–90 days under industrial conditions; tensile strength ~50–70 MPa, elongation at break ~6–15%; lower carbon footprint from algal feedstock compared to corn [115,118,119,120,121,122]	Food packaging, 3D printing, biomedical tools, disposable cutlery.	Scale limitations in algae cultivation raise costs compared to corn-based PLA.
Algal Nanocellulose	High tensile strength ~150 MPa; lightweight (density ~1.5 g/cm3); high crystallinity and thermal stability [123,124,125]	Bioplastic films, reinforced composites, biomedical uses.	Extraction complexity and scalability remain challenges.
Algae–Starch Composites	Tensile strength ~25–35 MPa; improved biodegradability compared to plant starch bioplastics [109,113,126]	Flexible packaging, disposable products.	Economically advantageous with minimal resource requirements for algae cultivation.
PHB/PLA Hybrids	Tensile strength ~45–70 MPa; improved toughness vs. pure PHB [127,128,129,130]	Packaging and consumer goods.	Potential to reduce brittleness while maintaining biodegradability.
Algae–Polyurethane Composites	Tensile strength > 60 MPa; high flexibility; improved biodegradability compared to conventional polyurethane [131,132,133,134]	Packaging films, durable consumer goods	Renewable-resource-based polyurethane with enhanced microbial degradation rates.
Algae–Polyvinyl Alcohol (PVA) Blends	Elongation at break up to 667%; high biodegradability [135,136,137,138]	Flexible packaging films.	Requires compatibilization to address miscibility issues.
Algae–Corn Gluten Meal Blends	Tensile strength ~40 MPa; improved flexibility and processability [109,139,140,141]	Packaging, agricultural films	Dual waste management benefits using agricultural by-products with algae cultivation.

Note: Where algal-specific production data is not yet available, values represent theoretical potential based on biomass composition and established microbial production systems, as outlined in the methodology (Section 2.6).

.

3.6. Comparative Performance Metrics and Data Limitations

To address the need for comparative assessment across algal bioplastic types, Table 3 compiles reported performance metrics from the reviewed literature. However, this compilation reveals a critical challenge in the field: the absence of standardized reporting frameworks for algal bioplastic production.

Unlike established bacterial PHA production systems, which routinely report volumetric productivities (g/L/h), substrate conversion efficiencies, and integrated techno-economic metrics, algal bioplastic studies employ diverse reporting approaches. Current literature typically presents endpoint concentrations (g/L) or biomass content (% DCW) rather than dynamic productivity rates (g/L/day) or areal yields (g/m²/day). This heterogeneity in data reporting reflects both the emerging nature of the technology (TRL 4–7) and the diversity of production systems, which range from direct cyanobacterial synthesis to multi-step processes using algal biomass as bacterial feedstock.

The data presented in Table 3 represents values directly reported in peer-reviewed studies. Where algal-specific data was unavailable—particularly for economic metrics and scaled productivity rates—we have noted these gaps rather than extrapolating from bacterial systems. For instance, while bacterial PHA production costs are well-documented at $4–6/kg [142,143], comparable data for integrated algal-to-PHA production remains absent from the literature. Similarly, while algal biomass production costs range from $1.13–2.04/kg, the additional processing steps required for bioplastic production have not been comprehensively analyzed in techno-economic studies.

This data compilation underscores an urgent need for the algal bioplastic community to adopt standardized reporting metrics that would enable meaningful cross-platform comparisons and accelerate technology development toward commercial viability. A performance metrics in Table 3 is provided for understanding the comparative performance of algal bioplastic systems.

Table 3. Reported Performance Metrics for Algal Bioplastic Systems from Literature.

Parameter	Value	Source/Context	Reference
PHB/PHA Production
PHB content in Chlorogloea fritschii	23% DCW	With sodium acetate supplementation	[144]
PHB concentration in cyanobacteria	1.2 g/L	Under optimized saline conditions	[145]
PHA content range	10–20% DCW	Current algal systems (stated in text)	Section 4.1
PHA degradation time	1.5–3.5 years	Ambient conditions	[48]
Lipid/TAG Production
TAG content in P. tricornutum	15% → 43% DCW	After TALEN mutagenesis	[146]
Grazing loss reduction	70%	B. braunii engineering	[147]
Hydrocarbon yield increase	35%	B. braunii engineering	[147]
Biomass Productivity
Chlamydomonas reinhardtii	>80 mg/L/day	iMAP platform screening	[148]
Carbohydrate Content
Chlorella vulgaris starch	12–17%		Section 3.2
Cladophora cellulose	20–30% DW	Stated in text	[56]
Mechanical Properties
Algal films tensile strength	12–25 MPa	From E. cottonii study	[103]
PLA tensile strength	50–65 MPa	Conventional PLA (for comparison)	[53]
Nanocellulose tensile strength	~150 MPa	Laboratory-produced films	[56]
Biodegradation
PLA composting	60–90 days	Industrial conditions	[56]
PHB marine degradation	46% mass loss in 160 days	At 29 °C	[149]
Technology Readiness
Algal PHA TRL	5–6	Current status	[150]
Algal PLA TRL	4–5	Current status	[150]
Economic Data
Bacterial PHA production cost	$4–6/kg	Not algal, but cited for comparison	Text states
Algal biomass production cost	$1.13–2.04/kg	General biomass, not bioplastic	[142,143]

Table 3. Reported Performance Metrics for Algal Bioplastic Systems from Literature.

Parameter	Value	Source/Context	Reference
PHB/PHA Production
PHB content in Chlorogloea fritschii	23% DCW	With sodium acetate supplementation	[144]
PHB concentration in cyanobacteria	1.2 g/L	Under optimized saline conditions	[145]
PHA content range	10–20% DCW	Current algal systems (stated in text)	Section 4.1
PHA degradation time	1.5–3.5 years	Ambient conditions	[48]
Lipid/TAG Production
TAG content in P. tricornutum	15% → 43% DCW	After TALEN mutagenesis	[146]
Grazing loss reduction	70%	B. braunii engineering	[147]
Hydrocarbon yield increase	35%	B. braunii engineering	[147]
Biomass Productivity
Chlamydomonas reinhardtii	>80 mg/L/day	iMAP platform screening	[148]
Carbohydrate Content
Chlorella vulgaris starch	12–17%		Section 3.2
Cladophora cellulose	20–30% DW	Stated in text	[56]
Mechanical Properties
Algal films tensile strength	12–25 MPa	From E. cottonii study	[103]
PLA tensile strength	50–65 MPa	Conventional PLA (for comparison)	[53]
Nanocellulose tensile strength	~150 MPa	Laboratory-produced films	[56]
Biodegradation
PLA composting	60–90 days	Industrial conditions	[56]
PHB marine degradation	46% mass loss in 160 days	At 29 °C	[149]
Technology Readiness
Algal PHA TRL	5–6	Current status	[150]
Algal PLA TRL	4–5	Current status	[150]
Economic Data
Bacterial PHA production cost	$4–6/kg	Not algal, but cited for comparison	Text states
Algal biomass production cost	$1.13–2.04/kg	General biomass, not bioplastic	[142,143]

4. Algal Strain Engineering for Bioplastic Production

While direct genetic engineering of algae for bioplastic production remains nascent, insights from bacterial systems provide roadmaps for algal development. The following discusses both achieved and potential applications in algal systems, drawing parallels from established microbial platforms where algal-specific data is limited. Algal strain engineering represents a cornerstone of innovation in sustainable bioplastic production, bridging fundamental algal biology with scalable, industry-relevant manufacturing processes. By combining genetic modifications, advanced genome-editing technologies, and pathway overexpression strategies, researchers have developed microalgal platforms capable of producing higher yields of bioplastic precursors such as polyhydroxyalkanoates (PHAs) and polylactic acid (PLA). These approaches not only enhance product titers but also improve the economic viability of algal bioplastics by optimizing carbon flux, reducing cultivation time, and integrating seamlessly into biorefinery models.

4.1. Genetic Modifications for PHA/PLA Precursors

Targeted genetic engineering has significantly advanced PHA and PLA synthesis in algal hosts by redirecting metabolic pathways toward key polymer precursors. In Pseudomonas putida, for example, reprogramming glucose metabolic routes has yielded optimized microbial chassis that can be integrated into algal systems to improve both biomass and PHA yields [151,152]. Such strategies often involve incorporating exogenous biosynthetic pathways into microalgae, enabling the production of tailored PHA structures with improved material properties [153].

Based on bacterial system analogs, theoretical PHA content increases of up to 35–50% of cell dry weight are targeted for engineered microalgae, though current algal systems achieve 10–20% DCW [154,155,156]. Synthetic biology has further enabled dynamic regulation of metabolic networks in Chlamydomonas reinhardtii, shifting cellular priorities from biomass accumulation toward PHA synthesis through targeted regulatory manipulation [157,158]. Additionally, optimization of lipid biosynthesis pathways—critical for generating fatty acid precursors—has resulted in improved yields for both PHA and PLA production [159].

4.2. CRISPR/Cas and Synthetic Biology Tools in Microalgae

The introduction of CRISPR/Cas genome-editing systems has revolutionized metabolic engineering in microalgae, offering unparalleled precision in altering target genes and metabolic pathways [160]. This technology enables targeted disruption or activation of genes to maximize the flow of carbon into desirable products. CRISPR/Cas9 interventions in Chlamydomonas have increased acetyl-CoA accumulation by 1.6-fold, elevating PHA titers to 1.5 g/L under heterotrophic cultivation [161]. While bacterial CRISPR applications have achieved transformation efficiencies exceeding 90%, microalgal applications currently reach 10–30% efficiency due to cell wall barriers and limited selection markers [162,163].

Complementary synthetic biology tools, including custom-designed gene circuits and regulatory modules, have enabled fine-tuning of expression levels for PHA-related enzymes, thus maintaining balanced growth and production phases [146]. Riboswitches, in particular, have emerged as adaptive regulatory elements that alter gene expression in response to intracellular metabolite levels, enhancing process control under varying cultivation conditions [146].

The integration of CRISPR/Cas systems with synthetic regulatory frameworks represents a powerful dual approach: genome editing delivers permanent genetic changes, while synthetic controls provide tunable production responses. Together, they position microalgae as robust, flexible production platforms for next-generation bioplastics.

4.3. Overexpression of Key Pathways

Overexpressing metabolic nodes central to PHA and PLA biosynthesis—most notably acetyl-CoA and lactate pathways—has proven to be an effective strategy for enhancing product yields in engineered algal systems. Acetyl-CoA is a pivotal precursor for fatty acid and polyester synthesis, and boosting its intracellular availability directly improves bioplastic titers. For instance, based on bacterial precedents, overexpression of acetyl-CoA synthetase genes could theoretically yield improvements of 25–40%, while in demonstrated algal systems, engineering Schizochytrium sp. with bacterial ACS led to ~30% increase in biomass and ~11% increase in fatty acid content, though expression stability and acetate accumulation remained challenges and with titers reaching up to 2.2 g/L in certain engineered microalgae [144,145,147,148].

Similarly, fine-tuning lactate metabolism supports dual optimization of biomass growth and polymer accumulation. Lactate functions as a carbon-rich substrate for microbial fermentation, and strains engineered for enhanced lactate utilization have demonstrated notable PHA productivity gains. Modulating the expression of lactate dehydrogenases and related enzymes can redirect metabolic flux toward polymer precursors without compromising cell viability. These targeted interventions exemplify how pathway overexpression can be leveraged to reinforce both yield robustness and process scalability in algal bioplastic production.

4.4. Case Studies in Algal Strain Engineering for Bioplastic Production

4.4.1. Enhanced Lipid Production Through Targeted Mutagenesis

Hao et al. (2018) demonstrated actual algal genetic engineering where the power of targeted genome editing in Phaeodactylum tricornutum by employing TALEN-based mutagenesis to inactivate a Hotdog-fold thioesterase gene [164]. This modification, paired with a two-phase cultivation strategy—initial nutrient-rich growth followed by nutrient stress—resulted in triacylglycerol (TAG) content increasing from 15% to 43% of DCW, representing nearly a threefold yield improvement. Beyond lipid accumulation, this work underscores the applicability of targeted mutagenesis to enhance metabolic pathways linked to bioplastic precursor synthesis.

4.4.2. Multi-Species Synergistic Engineering for Algal Grazing Protection

Thomas et al. (2024) introduced a community-based engineering approach, modifying Botryococcus braunii to deter grazers such as Daphnia and Poterioochromonas [165]. This represents actual algal cultivation system. The engineered strain served as a protective companion for high-value species like Nannochloropsis, simultaneously reducing grazing losses by up to 70% and increasing extracellular hydrocarbon yield by 35%. This multi-species system illustrates how genetic engineering can be extended beyond individual productivity gains to improve ecosystem resilience in algal cultivation, a critical factor for consistent industrial output.

4.4.3. Rapid Strain Selection via Integrated Microalgae Analysis Photobioreactor (iMAP)

Hong et al. (2016) developed the iMAP platform to accelerate strain screening, enabling high-throughput evaluation of Chlamydomonas reinhardtii for traits such as growth rate, lag time, and productivity [166]. Top-performing strains achieved biomass productivities exceeding 80 mg/L/day. This technological integration provides a bridge between laboratory-scale strain engineering and commercial strain selection, drastically reducing the time required to identify candidates for bioplastic production.

4.4.4. Novel Bioplastic Formulation from Marine Alga

Semary et al. (2022) investigated the marine green alga Eucheuma cottonii as a raw material for bioplastic production, combining its biomass with natural latex from Artocarpus altilis and Calotropis gigantea as plasticizers [109]. This approach yielded a composite with balanced mechanical integrity and biodegradability, demonstrating the potential of marine macroalgae in innovative bioplastic formulations. The study highlights how blending algal feedstocks with plant-derived plasticizers can expand the range of functional properties achievable in sustainable materials.

4.4.5. Polyhydroxybutyrate Production from Microalgae

Abdo & Ali (2019) evaluated PHB production across selected microalgal species, identifying Chlorogloea fritschii as a strong candidate when sodium acetate was supplemented in the growth medium [167]. This is direct microalgal PHB production. This intervention increased PHB content to 23% of DCW, a substantial improvement over baseline. The case underscores the role of relatively simple nutrient-level manipulations in boosting polymer accumulation, offering a cost-effective complement to more complex genetic engineering strategies.

4.4.6. Advances in Biopolymer Research and Development

Price et al. (2020) reviewed PHB production in cyanobacteria, emphasizing their adaptability to saline water and agricultural wastewater [168]. These cultivation conditions reduce freshwater competition and improve the sustainability profile of bioplastic feedstock production. Reported PHB concentrations reached 1.2 g/L under optimized saline conditions, demonstrating viable yields while opening avenues for expansion into non-arable and marginal lands.

Collectively, these case studies reveal the breadth of strategies available for algal strain engineering—ranging from targeted genome edits and pathway overexpression to community-level engineering and novel biomass formulations. Precision tools such as CRISPR/Cas and TALENs enable fine-tuned metabolic control, while cultivation innovations and mixed-species systems address real-world challenges like predation and cost-efficiency. The integration of synthetic biology, high-throughput screening, and tailored nutrient strategies points toward a future in which algal strains can be rapidly optimized for high-yield, cost-effective, and sustainable bioplastic production. However, commercial deployment will depend on bridging laboratory-scale success with scalable, economically viable production systems that can meet industrial demand while maintaining ecological integrity.

Table 4. Comparative Strategies in Algal Strain Engineering for Bioplastic Production.

Approach/Tool	Target Organism(s)	Genetic/Process Intervention	Key Outcome(s)	Reported Yield/ Improvement	Reference(s)
Targeted mutagenesis (TALEN)	Phaeodactylum tricornutum	Inactivation of Hotdog-fold thioesterase; two-phase cultivation (nutrient-rich → nutrient-stress)	Enhanced lipid accumulation for bioplastic precursors	TAG content ↑ from 15% → 43% DCW (~3× increase)	[164]
Multi-species engineered protection	Botryococcus braunii (companion for Nannochloropsis)	Genetic modifications to reduce grazer susceptibility	Reduced biomass loss; improved hydrocarbon output	Grazing loss ↓ 70%; hydrocarbon yield ↑ 35%	[165]
High-throughput strain screening (iMAP)	Chlamydomonas reinhardtii	Photobioreactor-based integrated analysis for growth & productivity metrics	Rapid identification of top-performing strains	Biomass productivity > 80 mg/L/day	[166]
Novel bioplastic blend formulation	Eucheuma cottonii	Biomass + natural latex plasticizers (Artocarpus altilis, Calotropis gigantea)	Balanced mechanical strength & biodegradability	Qualitative mechanical retention with renewable inputs	[109]
Nutrient supplementation for PHB	Chlorogloea fritschii	Sodium acetate addition to cultivation medium	Enhanced PHB biosynthesis	PHB ↑ to 23% DCW	[167]
Cyanobacterial saline cultivation	Cyanobacteria (various)	Growth in saline & wastewater media	PHB production with reduced freshwater demand	PHB up to 1.2 g/L under saline conditions	[168]
Pathway overexpression–acetyl-CoA	Microalgae (engineered)	Overexpression of acetyl-CoA synthetase	Increased precursor availability for PHAs/PLAs	PHA yield ↑ 25–40%; up to 2.2 g/L	[144,147,148,169]
Lactate pathway optimization	Microalgae (engineered)	Enzyme modulation for lactate utilization	Balanced biomass & polymer accumulation	Improved PHA titers (quantitative gains context-dependent)	[170]
CRISPR/Cas metabolic rerouting	Chlamydomonas reinhardtii	Knockouts to boost acetyl-CoA flux	Increased polymer precursor synthesis	Acetyl-CoA ↑ 1.6×; PHA titer up to 1.5 g/L	[171,172,173]
Riboswitch-based pathway control	Microalgae (various)	Conditional gene expression in response to metabolites	Fine-tuned polymer synthesis without growth penalty	Qualitative yield and growth improvements	[174,175,176,177,178,179,180]

and Figure 3 combinedly show genetic and metabolic engineering strategies for enhanced algal bioplastic production.

5. Fermentative Bioplastic Production Routes

This section examines three fermentation strategies: (1) using algal biomass as feedstock in established bacterial systems, (2) emerging algal-specific fermentation processes, and (3) theoretical applications based on algal metabolic capabilities. Fermentation-based conversion of algal biomass represents one of the most promising avenues for producing biodegradable plastics at scale. These processes leverage algae as either a feedstock or a host organism, with pathways differing in microbial systems, substrate processing requirements, and achievable product yields. This section reviews three major fermentative routes—heterotrophic fermentation, dark fermentation, and direct algal biosynthesis—while providing a comparative assessment of their performance, scalability, and limitations.

5.1. Heterotrophic Fermentation

Recent advances in heterotrophic fermentation of organic carbon sources—including algal biomass hydrolysates and lignin-derived substrates—have significantly improved reported PHA production metrics. Engineered bacterial strains such as Cupriavidus necator and Pseudomonas putida have achieved PHA titers of up to 1.4 g L⁻¹ under optimized conditions, including co-utilization of lignin-derived carbon sources [181]. Wang et al. (2024) demonstrated volumetric productivities 0.7 g L⁻¹ day⁻¹ surpassing earlier reports of 0.2–0.5 g L⁻¹ day⁻¹ under less optimized fermentation regimes [181]. These improvements underscore the importance of substrate preconditioning, metabolic engineering, and process control in achieving higher PHA accumulation.

Yield efficiencies of up to 0.65 g PHA per g sugar have been reported in optimized synthetic feedstock systems, providing a useful benchmark for algal hydrolysate-based fermentation, where similar yields may be attainable as pretreatment and saccharification efficiencies improve [182,183]. Pretreatment strategies such as alkaline or dilute acid hydrolysis, followed by enzymatic saccharification, typically achieve 70–85% glucose conversion efficiency, increasing fermentable sugar availability for downstream fermentation. Maintaining an optimal C/N ratio—often ≥ 10:1—has been shown to promote both biomass accumulation and PHA synthesis, with nitrogen limitation effectively channeling carbon flux toward polymer production [184]. Together, these parameters provide a framework for developing efficient heterotrophic fermentation processes using algal biomass as a sustainable carbon source.

5.2. Dark Fermentation

Dark fermentation of algal biomass is an efficient route for producing volatile fatty acids (VFAs), which can be converted into polyhydroxyalkanoates (PHAs). Key algal feedstocks include Chlorella vulgaris and Scenedesmus obliquus, whose high carbohydrate content enables strong acidogenic performance. For instance, S. obliquus co-fermented with municipal sludge achieved 28 g L⁻¹ of VFAs, with downstream Cupriavidus necator conversion yielding ~ 30% PHA [185,186].

Reported VFA yields vary with strain and process configuration: C. vulgaris alone can reach ~20 g L⁻¹ (25% PHA conversion), while mixed cultures of S. obliquus and C. vulgaris have achieved ~35 g L⁻¹ with conversion rates > 30% [187,188]. High-performing systems, particularly those employing advanced pretreatment, report up to 40 g L⁻¹ from Nannochloropsis sp., setting an upper benchmark for algal dark fermentation [189].

Optimal operation typically requires pH 6.5–7.5, mesophilic temperatures (~35 °C), and hydraulic retention times of 48–72 h to maximize VFA production while avoiding acid inhibition [190,191]. Co-fermentation with organic wastes at a 1:1 ratio further improves yields [192].

Synergistic interactions enhance system performance: co-fermentation with Clostridium butyricum increases butyrate and acetate production while reducing inhibitory by-products, significantly boosting VFA output over axenic cultures [193]. However, VFA concentrations above ~10 g L⁻¹ can inhibit algal growth, necessitating careful process control [194].

Collectively, these findings highlight dark fermentation as a viable strategy for coupling algal biomass valorization with bioplastic production. Improved strain selection, pretreatment, and mixed-culture management will be critical to reaching industrially competitive PHA yields.

5.3. Algae as Host Organisms for Direct Bioplastic Synthesis

The use of algae such as Chlamydomonas reinhardtii as direct hosts for bioplastic synthesis is an emerging strategy aimed at bypassing traditional bacterial fermentation. Genetic engineering and metabolic optimization have enabled C. reinhardtii to accumulate substantial lipid reserves, providing precursors for polyhydroxyalkanoate (PHA) and polylactic acid (PLA) synthesis.

Under nitrogen limitation, C. reinhardtii can accumulate up to ~30% of DCW as lipids, which can be redirected toward bioplastic pathways [195]. Controlled photobioreactor cultivation with optimized light and nutrient regimes has achieved lipid productivities of ~0.5 g L⁻¹ day⁻¹ [196]. Advanced chloroplast transformation systems and synthetic biology tools, including riboswitch-based regulation, have been developed to enhance PHA precursor biosynthesis and metabolic flux toward target pathways [146].

Co-cultivation further improves performance: pairing C. reinhardtii with acetate-producing Synechococcus sp. PCC 7002 increased biomass and lipid accumulation by providing a continuous carbon source [197]. These symbiotic systems reduce nutrient input requirements and can improve overall bioplastic precursor yield.

Compared with conventional bacterial producers like Cupriavidus necator (which can accumulate up to 90% DCW as PHA), algal systems currently exhibit lower polymer accumulation. However, they benefit from direct CO₂ fixation, lower operating costs, and the potential for integration with wastewater treatment and renewable energy systems, making them attractive for sustainable large-scale production [198,199].

Finally, environmental factors such as light intensity and photoperiod significantly influence metabolic fluxes in C. reinhardtii. Optimizing these parameters can enhance carbon partitioning toward PHA precursors, as supported by metabolic modeling and experimental studies [200]. Continued progress in strain engineering, pathway balancing, and reactor design is expected to narrow the gap between algal and bacterial systems and enable commercially competitive algal-based bioplastic production.

5.4. Comparative Assessment of Fermentative Routes for Bioplastic Production

Fermentative bioplastic production can be approached via multiple routes, each with distinct feedstock requirements, product yields, and operational advantages. Among these, heterotrophic fermentation, dark fermentation, and direct algal biosynthesis are the most prominent pathways currently under investigation. Heterotrophic fermentation utilizes algal biomass hydrolysates rich in fermentable sugars, enabling efficient microbial production of PHAs, whereas dark fermentation leverages mixed microbial cultures to convert organic wastes into volatile fatty acids (VFAs) subsequently transformed into PHAs. Direct algal biosynthesis, in contrast, relies on genetically engineered algal hosts that synthesize PHAs intracellularly, reducing downstream processing complexity.

A summary comparison of these fermentative strategies, based on reported experimental outcomes, is presented in

Table 5. Comparative metrics for fermentative bioplastic production routes using algal biomass.

Route	Feedstock	Reported Product Yields	Key Advantages	Main Challenges	References
Heterotrophic Fermentation	Algal biomass hydrolysates (enzymatically or chemically pretreated)	~30 g/L fermentable sugars; PHA titers up to 250 mg/L (C/N ratio dependent)	High sugar conversion efficiency (70–85% glucose recovery); scalable process knowledge from industrial fermentations	Cost of enzymatic pretreatment; potential inhibitory compounds in hydrolysates	[201,202]
Dark Fermentation	Co-fermentation of algal biomass with food/agro-waste	4–7 g/L VFAs; PHA yield ~8 g/L (strain & mode dependent)	Valorizes multiple waste streams; robust mixed-culture metabolism	Optimization of VFA-to-PHA conversion; controlling microbial community dynamics	[183,203]
Direct Algal Biosynthesis	Engineered microalgae (e.g., Pseudomonas putida pathways integrated into algal hosts)	PHA content up to 20% CDW; productivity ~1.06 g/L/day	Eliminates need for separate fermentation step; lower substrate preparation costs	Genetic stability of engineered strains; scale-up challenges	[204,205,206,207]

.

5.5. Process Optimization Strategies for Fermentative Routes

Optimizing fermentative routes for algal bioplastic production requires fine-tuning both upstream and fermentation parameters to maximize yields and minimize costs. In heterotrophic fermentation, pretreatment conditions directly influence the accessibility of fermentable sugars. Enzymatic saccharification efficiencies ranging from 70 to 85% glucose recovery have been reported, with optimal enzyme loading and hydrolysis times significantly impacting downstream PHA titers [208]. Adjusting the carbon-to-nitrogen (C/N) ratio during fermentation can increase PHA accumulation from algal hydrolysates to levels approaching 250 mg/L [209].

For dark fermentation, maintaining stable microbial community dynamics is critical to achieving VFA yields of 4–7 g/L and conversion efficiencies of 30–60% under optimized pH, substrate ratio, and hydraulic retention time conditions [188,210]. Integration of pH-controlled reactors with continuous feeding strategies has shown potential for enhancing VFA productivity and subsequent PHA synthesis.

In direct algal biosynthesis, metabolic engineering of pathways leading to acetyl-CoA and fatty acid synthesis has enabled PHA productivities of ~1.06 g/L/day and intracellular contents of 20% CDW under controlled photobioreactor conditions [144]. Further improvements are linked to genetic stability and expression control in engineered strains, ensuring consistent performance during large-scale cultivation [151].

5.6. Integration into Circular Bioeconomy Frameworks

Fermentative algal bioplastic production aligns closely with the principles of the circular bioeconomy, where waste valorization, resource efficiency, and product end-of-life are integrated into the design stage. Heterotrophic and dark fermentation routes can be embedded within biorefinery schemes, where residual biomass after sugar or VFA extraction is converted into biofertilizers, bioenergy, or high-value co-products, thereby improving process economics [188]. This integration minimizes waste streams while leveraging synergies between multiple product lines.

Direct algal biosynthesis offers further potential for decentralized, low-footprint production systems, particularly in coastal or non-arable land regions. By combining engineered algae with wastewater nutrient recovery, production systems can simultaneously address environmental remediation and bioplastic synthesis [211].

The scalability of these processes will depend on techno-economic assessments that account for production costs (USD/kg), GHG emissions (kg CO₂-eq/kg), and biodegradation performance relative to petrochemical plastics. Aligning these metrics with policy incentives, extended producer responsibility (EPR) schemes, and consumer awareness campaigns will be critical to accelerating the market penetration of algae-derived bioplastics.

6. Downstream Processing

The downstream processing of algal biomass for the recovery of polyhydroxyalkanoates (PHAs) and polylactic acid (PLAs) is a critical determinant of the technical feasibility and economic viability of bioplastic production. Efficient recovery methods not only influence polymer yield and purity but also have significant implications for cost structure, scalability, and environmental performance. The choice of method depends on multiple factors, including polymer characteristics, desired application, processing economics, and integration within a biorefinery framework.

6.1. Extraction of PHAs and PLAs from Algal Biomass

Algal biomass provides a versatile feedstock for bioplastic extraction due to its high growth rates, adaptability to diverse cultivation environments, and potential for co-product recovery. Recent studies emphasize biorefinery-based approaches that maximize product streams while minimizing environmental impacts [212]. Extraction yields from bacterial PHA production systems range from 30 to 60 mg PHA g⁻¹ dry biomass, with similar recovery expected from algal systems pending optimization, with species selection, cultivation regime, and pretreatment strategies significantly affecting recovery efficiency [213]. Co-products such as pigments, lipids, and polysaccharides—comprising up to 20% of biomass dry weight—can enhance economic returns and support circular bioeconomy models [109,126].

6.2. Solvent-Based, Enzymatic, and Mechanical Recovery Approaches

Current recovery technologies can be broadly categorized into solvent-based, enzymatic, and mechanical methods. Solvent extraction remains widely employed, particularly where high recovery yields (65–85%) and polymer purities (>90%) are required [214,215]. The choice of solvent—ideally low-toxicity and recyclable—affects both environmental footprint and operational cost. Enzymatic extraction achieves purities exceeding 95% but is often limited by higher process costs (up to USD 3.50 kg⁻¹ polymer) and scalability constraints [113,216]. Mechanical methods, such as bead milling or high-pressure homogenization, offer cost efficiency and reduced chemical use, but typically achieve lower recoveries (40–60%) and purities (≤70%) [217,218].

6.3. Purity, Scalability, and Cost-Efficiency

Achieving a balance between polymer purity, process scalability, and cost-efficiency remains a central challenge in algal bioplastic downstream processing. Integrated approaches—such as sequential enzymatic and solvent extraction—have demonstrated purities exceeding 92%, meeting the specifications for high-value applications, including medical-grade materials [126]. However, process economics are strongly scale-dependent: while laboratory systems rarely exceed 100 g day⁻¹ polymer output, pilot-scale photobioreactor-based systems have achieved production rates of 5–10 kg day⁻¹ [219,220]. Downstream operations can account for 25–45% of total production costs, estimated at USD 1.20–1.80 kg⁻¹ PHA depending on energy inputs, solvent recovery strategies, and integration with co-product valorization [221,222]. Cost optimization is often pursued through waste valorization pathways, which can offset processing expenses while improving environmental performance.

6.4. Waste Valorization Options

Waste valorization within algal bioplastic production systems presents opportunities to enhance both sustainability and profitability. Anaerobic digestion of residual algal biomass yields between 180 and 320 L CH₄ kg⁻¹ volatile solids (VS), contributing to on-site bioenergy production and reducing disposal burdens [223,224]. The nutrient-rich digestate or untreated biomass can be applied as organic fertilizer, typically containing 4–6% nitrogen, 1–2% phosphorus, and 3–5% potassium on a dry-weight basis [225]. Life cycle assessment (LCA) studies indicate that integrating waste valorization can reduce the net carbon footprint of algal-derived bioplastics by 0.8–1.5 kg CO₂-eq kg⁻¹ polymer produced [226]. These pathways not only support a circular bioeconomy but also contribute to compliance with tightening sustainability regulations in global markets.

Table 6. Comparative assessment of downstream processing methods for PHA/PLA recovery from algal biomass.

Method	Mechanism	Target Polymer(s)	Recovery Yield (%)	Purity (%)	Processing Time (h)	Scalability	Cost-Efficiency	Environmental Impact	TRL *	Residue Valorization Potential	Key Limitation
Solvent Extraction	Dissolves target polymers from algal biomass using solvents, followed by separation and precipitation.	PHAs, PLAs	60–95 [227]	80–95	1–5	High	Moderate	Moderate; solvent use & toxicity	5	Residues usable for fertilizer or biogas [228,229]	Solvent toxicity and disposal issues
Enzymatic Digestion	Enzymes degrade cell walls, releasing PHAs/PLAs.	PHAs	40–70 [230,231]	85–95	6–24	Moderate	Moderate	Low toxicity	5	Animal feed or soil amendment [232,233]	Inconsistent yields between biomass types
Mechanical Disruption (e.g., bead milling)	Physical disruption of algal cells to release intracellular polymers.	PHAs, PLAs	30–50 [234,235]	70–90	1–2	Moderate	Moderate	High; minimal solvents	4	Residues converted to bioenergy [236,237,238,239]	Energy-intensive equipment
Supercritical CO2 Extraction	Uses supercritical CO2 to solubilize polymers with minimal solvents.	PHAs, PLAs	70–95 [150,240,241,242]	90–98	3–6	High	High	Low emissions	7	Residues usable for biofuel/fertilizers [243]	High equipment cost
Chemical Digestion (acid/alkali)	Chemical agents degrade biomass to release polymers.	PHAs	50–80 [244,245]	70–90	2–4	Moderate	Low	Moderate; hazardous chemicals	5	Compost or biogas production [246]	Hazardous chemical handling
Microwave-Assisted Extraction	Microwave energy heats and disrupts cells, enhancing polymer release.	PHAs, PLAs	60–80 [247,248]	80–95	0.5–2	High	Moderate	Low energy use	6	Residues usable as biofertilizers [249]	Specialized equipment required
Electrochemical Methods	Electrical energy facilitates polymer release from biomass.	PHAs, PLAs	50–70 [250,251,252]	75–90	1–3	Moderate	Moderate	Moderate; energy-intensive	4	Feed or compost [250,251]	Limited commercial application

* Data primarily derived from bacterial PHA/PLA production systems; algal-specific extraction studies remain limited to laboratory scale.

shows comparative assessment of downstream processing methods for PHA/PLA recovery from algal biomass.

7. Industrial Applications and Products of Algal Fermentation in Bioplastics

7.1. Bioplastic Packaging

Current commercial bioplastic packaging utilizes bacterial-produced PHAs, with algal alternatives under development at pilot scale to conventional fossil-fuel-derived plastics, directly addressing packaging waste and aligning with circular economy principles [113]. Compared to starch-based films, algal films exhibit higher tensile strength (12–25 MPa vs. 3–10 MPa) and lower water absorption (<15% after 24 h), improving barrier properties and durability [109,113]. These performance gains, coupled with reduced reliance on agricultural land and freshwater, position algae-derived materials as competitive candidates for packaging applications in food, retail, and consumer goods sectors.

7.2. Biomedical Applications

In medical applications, algae-derived PHAs demonstrate both biocompatibility and biodegradability, supporting their use in sutures, implants, and tissue scaffolds [168,253]. In vivo data show 90–100% biodegradation within 30–90 days under physiological conditions, while cytotoxicity tests maintain >85% cell viability, satisfying ASTM F748-06 standards [254,255]. Engineered algal strains with enhanced PHA production capacity allow for controlled polymer characteristics, enabling tailored degradation rates and mechanical performance for surgical and regenerative applications [126,256].

7.3. 3D Printing, Films, and Automotive Parts

Algal bioplastics extend into additive manufacturing, film production, and lightweight automotive components. Filaments derived from algal polymers possess densities around 1.2 g/cm³ and tensile moduli between 700 and 1500 MPa, competitive with PLA and ABS [108,257]. Under composting conditions, these materials achieve full biodegradation within 120 days. Cost estimates for emerging algal-based filaments range from $2.50–4.00/kg, approaching parity with established bioplastics. In automotive applications, weight reduction from biopolymer substitution supports improved fuel efficiency, while films from algal sources combine mechanical integrity with compostability, making them suitable for packaging and interior components [258,259].

7.4. Case Studies

7.4.1. Algix

Algix develops bioplastics from algal biomass—particularly Spirulina and Chlorella—sourced from aquaculture and wastewater streams, converting nutrient-rich effluents into feedstock [113,260]. Currently they use algal biomass as filler material rather than for direct bioplastic production. Their flagship BLOOM^® TPE and BLOOM^® Foam replace portions of petroleum-derived EVA in footwear and sports products, maintaining durability and resilience while reducing petroleum use. The process removes excess algae from aquatic environments, delivering environmental co-benefits beyond material substitution [142].

7.4.2. Loliware

Loliware use macroalgae (seaweed) extracts, representing one of the few commercial algae-based bioplastic products. They manufacture compostable straws and utensils from seaweed-derived biopolymers, leveraging marine biomass that requires no arable land, freshwater, or synthetic fertilizers [143,261]. Products match the mechanical strength and heat resistance of petroleum-based cutlery while offering industrial compostability and, in some cases, environmental biodegradation. This approach addresses single-use plastic pollution and aligns with emerging regulatory bans on petroleum-based disposables [262,263].

7.4.3. Cladophora Bioplastics

Cladophora algae provide high-crystallinity cellulose suitable for durable bioplastic composites [264,265]. Using hydrogel-based processing with epichlorohydrin as a cross-linker, these composites improve stiffness and tensile strength, addressing brittleness challenges common in bio-based films. Applications include specialty packaging and consumer products where mechanical performance and sustainability must co-exist. Important industrial applications have been tabulated in

Table 7. Comparative Summary of Industrial Applications and Products of Algal Bioplastics.

Application/ Product Category	Feedstock Source	Key Mechanical Properties	Biodegradation Timeline & Conditions	Approx. Cost Range (USD/kg)	Example Commercial Products	Selected References
Bioplastic Packaging	Microalgae (e.g., Chlorella, Spirulina)	Tensile strength typically 12–25 MPa (varies by formulation); water absorption often <15% (24 h)	60–180 days in composting (varies by formulation and processing)	Cost varies; estimates suggest higher than petro-plastics; see market reports	Algal-based films, molded packaging	[109,113,227]
Biomedical Applications	PHA-producing microalgae; engineered strains	Biodegradation and cell viability depend on polymer type and formulation; tested per ASTM F748 guidance in biomedical contexts	Physiological conditions; in vitro/in vivo results vary (see cited studies)	Higher than commodity plastics; specialized biomedical grade pricing applies	Biodegradable sutures, scaffolds	[266,267,268,269,270]
3D Printing & Automotive Parts	Algal biopolymers, PHA blends	Density ~1.2 g/cm3; tensile modulus typically 0.7–1.5 GPa for PLA blends	~120 days in composting (PLA blends)	Cost varies; currently above petro-based equivalents	Algal-PLA filaments, lightweight panels	[64,113,253]
Algix—BLOOM® Foam	Spirulina, Chlorella (from aquaculture/wastewater)	Comparable to EVA in resilience and elastic recovery	Not biodegradable; biomass content offsets fossil EVA use	Not publicly disclosed	BLOOM® Foam, BLOOM® TPE	[113,271]
Loliware	Seaweed (macroalgae)	Stiffness & heat tolerance comparable to conventional cutlery	Home/industrial compostable; company claims partial marine degradability	Not publicly disclosed	Compostable straws, utensils	[143,261,262]
Cladophora Bioplastics	Cladophora cellulose	High-crystallinity cellulose composites; improved modulus & tensile strength	Biodegradation varies by formulation; some show rapid mass loss in lab tests	Not publicly disclosed	Specialty packaging, consumer goods	[264,265,272]

.

8. Techno-Economic Analysis and Life Cycle Assessment

8.1. Cost Comparison: Algae-Based vs. Petroplastic vs. Other Bioplastics

A comprehensive techno-economic analysis (TEA) indicates current bacterial PHA production costs range from $4–$6/kg, compared to $1–$2/kg for petrochemical plastics. While algal biomass production costs $1.13–$2.04/kg, specific techno-economic analyses for complete algal-to-PHA production are lacking in peer-reviewed literature [273,274]. Extrapolating from biomass costs and required processing steps suggests total costs would substantially exceed bacterial production. These costs are competitive with other bioplastics at TRL 8–9 (e.g., PLA, starch blends), which range from $2.0–$4.50/kg, but still above petrochemical plastics at TRL 9 (fully commercial), which cost $0.90–$2.20/kg [109,258]. Integration with wastewater treatment and other biorefinery systems can reduce algae-based production costs by up to 20–30%, with added environmental benefits and potential carbon credit revenues [275]. As TRL advances toward 8–9, economies of scale are expected to close the cost gap with petroplastics.

8.2. Key Metrics: GHG Emissions, Land/Water Use, Energy Consumption

Life cycle assessments (LCA) show that algae-based bioplastics at TRL 6–7 emit 2–3 kg CO₂-eq/kg of product, substantially lower than petroplastics at TRL 9 (6.0–9.0 kg CO₂-eq/kg) and marginally better than other bioplastics at TRL 8–9 (2.5–4.0 kg CO₂-eq/kg) [113,276,277].

Water use is also favorable at 15–20 L/kg, compared to 45–120 L/kg for petroplastics and 30–80 L/kg for other bioplastics [278,279]. However, the higher energy consumption seen in TRL 6–7 algae systems (5–10 MJ/kg) versus mature TRL 9 petroplastics (20–25 MJ/kg) reflects the process intensification still required for algae to fully realize efficiency gains at commercial scale.

8.3. Challenges in Feedstock Availability, Yield, Productivity

Current productivity for algae-based bioplastics at TRL 6–7 is 45–80 g/m²/day, compared to 120–190 g/m²/day for TRL 9 petrochemical systems and 40–90 g/m²/day for other bioplastics at TRL 8–9 [126,280]. Yield variability is strongly linked to climate sensitivity, cultivation system design, and the absence of fully optimized large-scale operations. Achieving TRL 8–9 performance will require genetic strain improvement, robust climate-resilient systems, and automation to stabilize yields under varied environmental conditions, thereby making algae feedstock supply more predictable for industrial demand. Techno-economic and life cycle metrics for algae-based and other bioplastics have been presented in Table 8.

8.4. Policy and Market Incentive

The TRL stage of a technology directly influences policy uptake and investment risk. Algae-based plastics at TRL 6–7 stand to benefit most from targeted subsidies, carbon credit programs, and preferential procurement policies, which can help accelerate the transition to TRL 8–9. Global single-use plastic bans and extended producer responsibility (EPR) regulations are already pushing high-TRL (8–9) bioplastics into mainstream markets, and similar frameworks can provide algae-based products with the commercial push needed to compete with TRL 9 petroplastics [275,281]. Strategic partnerships with high-volume sectors (e.g., packaging, automotive) can further reduce scaling barriers.

Table 8. Comparative Analysis of Techno-Economic and Life Cycle Metrics for Algae-Based, Petrochemical, and Other Bioplastics.

Metric	Algae-Based Bioplastics (TRL 6–7)	Petrochemical Plastics (TRL 9)	Other Bioplastics (TRL 8–9)
Production Cost ($/kg)	$1.30–$3.50	$0.90–$2.20	$2.0–$4.
GHG Emissions (kg CO2-eq/kg)	2–3	6.0–9.0	2.5–4.0
Water Usage (L/kg plastic)	15–20	45–120	30–80
Energy Consumption (MJ/kg)	5–10	20–25	12–18
Commercial Maturity (TRL)	6–7 (Pilot to early commercial)	9 (Fully commercial)	8–9 (Late-stage commercial)

This table was created using peer review articles and market research data [64,113,149,258,276,282,283,284,285,286,287,288,289,290,291,292].

Table 8. Comparative Analysis of Techno-Economic and Life Cycle Metrics for Algae-Based, Petrochemical, and Other Bioplastics.

Metric	Algae-Based Bioplastics (TRL 6–7)	Petrochemical Plastics (TRL 9)	Other Bioplastics (TRL 8–9)
Production Cost ($/kg)	$1.30–$3.50	$0.90–$2.20	$2.0–$4.
GHG Emissions (kg CO2-eq/kg)	2–3	6.0–9.0	2.5–4.0
Water Usage (L/kg plastic)	15–20	45–120	30–80
Energy Consumption (MJ/kg)	5–10	20–25	12–18
Commercial Maturity (TRL)	6–7 (Pilot to early commercial)	9 (Fully commercial)	8–9 (Late-stage commercial)

This table was created using peer review articles and market research data [64,113,149,258,276,282,283,284,285,286,287,288,289,290,291,292].

8.5. Regional Policy Landscape

The global landscape for bio-based materials shows significant regional differences. In the EU, the Single-Use Plastics Directive (2019) bans certain plastic items and promotes bioplastics, creating economic opportunities despite debated projections [293]. The Horizon Europe program further commits €95 billion to bio-based industries, reinforcing sustainable manufacturing [294].

In the U.S., the USDA BioPreferred Program incentivizes bio-based products and offers tax credits— such as “$1.01 per gallon for bio-based chemicals” require verification against USDA documentation [295,296]. These policies strengthen the U.S. bioeconomy and global competitiveness.

Asia focuses on innovation-driven bioeconomy expansion. China’s 14th Five-Year Plan targets major plastic reduction, though they had a target of “25%”, the achieved result is not confirmed [297,298]. Japan’s Bioplastics Roadmap sets production targets, underscoring bioplastics’ role in waste reduction [293].

While these initiatives advance sustainability, they also fragment markets. Differing regulations force companies to navigate complex, localized compliance strategies, highlighting the need for harmonized global standards [294,299].

9. Challenges and Limitations

9.1. Economic & Technical Barriers

The large-scale production of algal bioplastics faces intertwined economic and technical bottlenecks that limit competitiveness against petroleum-based plastics. While bacterial production has overcome cultivation challenges through high-density fermentation, algal systems still face photobioreactor scaling limitations, with controlled-environment growth systems estimated at $0.85–$1.50/kg biomass [300,301]. Harvesting methods such as centrifugation or flocculation can contribute an additional $0.60–$1.00/kg plastic [302,303]. Combined, these factors place algal plastic production at $1.70–$2.50/kg, compared to $0.90–$2.20/kg for petroplastics [304,305].

Industrial scaling is further constrained by infrastructure costs: pilot facilities typically operate below 1000 tons/year capacity, while commercial-scale plants require >$20 million USD capital investment [258]. Economic viability often demands biomass productivities exceeding 100 g/m²/day or 6–8 g/L in fermenters, levels rarely achieved without co-product valorization [306].

Even at current TRL 6–7, product quality variability remains an obstacle. Differences in algal species, cultivation parameters, and extraction methods yield inconsistencies in tensile strength, biodegradability, and moisture resistance [113]. This variability complicates standardization and supply chain reliability, limiting adoption in performance-critical markets.

9.2. Biological & Material Stability Challenges

The production of high-performance algal bioplastics increasingly relies on genetically engineered microalgae, particularly for polyhydroxyalkanoate (PHA) yields. However, these systems, often using CRISPR/Cas9 or other genetic engineering tools, can exhibit genetic instability. Genetic instability observed in bacterial systems (trait loss after 50–100 generations) suggests similar challenges for algal platforms, with preliminary studies showing 30–40% expression loss within 20 generations—including unintended mutations, trait loss, or reversion to wild-type phenotypes [17,155,307].

This instability leads to fluctuations in productivity, altered polymer composition, and reduced mechanical performance. Compounding this are biological variabilities across strains—two cultures of the same engineered species grown under different nutrient or light regimes can produce polymers with significantly different crystallinity, elongation, or degradation rates [126].

At present, most engineered strain systems are operating at TRL 4–6, with ongoing research into stabilizing genetic vectors, improving trait inheritance over successive generations, and creating process controls that maintain polymer uniformity. Without these advances, scaling production risks inconsistent quality, increased waste, and higher per-unit costs.

9.3. Policy, Infrastructure & Market Integration

The industrial adoption of algal bioplastics is strongly influenced by policy frameworks, infrastructure readiness, and market awareness. Currently, no globally harmonized regulations exist for the production, labeling, and end-of-life management of algal-derived bioplastics [258]. This regulatory gap limits investment confidence, slows market integration, and complicates waste management, particularly in regions where bioplastics are not integrated into existing recycling or composting systems.

Infrastructure constraints are equally limiting. Many regions lack biorefinery facilities capable of processing algal biomass at industrial scales, and existing plastic manufacturing lines are optimized for petrochemical feedstocks [64]. As a result, algal bioplastics often require separate processing lines, adding to production costs.

Consumer acceptance remains a softer but crucial barrier. Misunderstanding of terms like biodegradable vs. compostable contributes to improper disposal and skepticism about performance [256]. At TRL 6–8, these barriers are less about technical feasibility and more about market readiness—necessitating coordinated policy incentives, investment in infrastructure, and targeted education campaigns to drive adoption.

9.4. Environmental Fate & Marine Biodegradability

Algal-based bioplastics such as PHB can demonstrate promising marine degradation rates—losing up to 46% mass in 160 days at 29 °C, with complete degradation in ~350 days [308]. However, performance varies dramatically by polymer type and environmental conditions. For example, PLA degrades only 5–10% in 60–90 days in marine environments below 25 °C, limiting its short-term pollution mitigation potential [309].

Marine degradation depends on salinity, temperature, and microbial community structure. Even biodegradable plastics can produce microplastics (<5 mm) if degradation is incomplete, with certain PLA–algal blends persisting > 180 days in sediments [310]. Optimizing polymer composition to exceed 90% degradation without harmful byproducts remains a priority for environmental safety.

Current marine biodegradation systems for algal bioplastics are at TRL 4–6, indicating early-stage field validation. Scaling these technologies will require integrated LCA–ecotoxicity assessments to ensure that marine safety claims are credible and verifiable under varied real-world conditions.

Table 9. Consolidated Challenges, TRLs, and Key Metrics for Algal Bioplastics.

Challenge Category	Key Issues & Metrics	Representative TRL	Notes/ References
Production Economics	Cultivation & harvesting cost: $0.85–$1.50/kg biomass; total production $1.70–$2.50/kg vs. petroplastics $0.90–$2.20/kg	5–7	[311,312]
Biological & Technical Reliability	Low transformation efficiency across microalgae species; challenges with stable genetic integration; strain-dependent variability in modification success; limited genetic toolbox compared to other microorganisms	4–6	[313,314]
Quality Consistency	Variability in mechanical & biodegradability metrics due to biomass source, cultivation conditions; impurity risks from extraction	5–7	[315,316]
Scale-up Infrastructure	Limited commercial-scale photobioreactors; high capital requirements (250,000–272,000 USD/hectare); energy-intensive processing; labor-intensive installation; biomass costs exceed terrestrial alternatives	6–8	[314,317,318]
Policy & Market Integration	Lack of harmonized regulations; infrastructure not designed for algal feedstocks; low consumer awareness; disposal confusion	6–8	[160,314]
Environmental Fate & Marine Biodegradability	PHB: 54–58% loss in 160 days in seawater; PLA: minimal degradation in marine conditions; microplastic risks from incomplete breakdown; biodegradation highly environment-dependent	4–6	[319,320,321,322,323,324]

shows challenges and status of algal bioplastics.

9.5. Environmental and Biodiversity Considerations

Large-scale algal cultivation offers sustainability potential but also poses significant ecological risks. Genetic escape remains a key concern, as engineered algal strains may outcompete native species and disrupt biodiversity through gene flow or competitive dominance [325]. Seaweed farms can shift local species dynamics, further promoting cultivated strains if unmanaged [325].

Water use is another critical issue. Even when using non-potable water, large farms may lower local water tables and disrupt hydrological cycles, risking conflict with surrounding freshwater users [326]. Sustainable water management and hydrological assessments are therefore essential.

In marine settings, cultivation can alter nutrient cycling, affecting benthic communities reliant on stable nutrient inputs [327]. Introducing non-native species also raises the risk of biological invasions with long-term ecosystem consequences [325,328].

Mitigation measures include closed-system cultivation and genetic containment strategies to prevent escape, along with comprehensive environmental impact assessments before introducing new species or techniques [329,330]. These approaches help balance algal cultivation’s benefits with ecological protection.

10. Future Prospects and Recommendations

10.1. Integrated Biorefineries and Wastewater Synergies

The development of algal bioplastics will increasingly benefit from integrated biorefinery systems that convert biomass into multiple high-value products—including biofuels, bioplastics, and nutraceuticals—through coordinated biochemical and thermochemical processes. Such systems enable component fractionation and valorization, improving yield, efficiency, and profitability [331,332,333]. Advanced processing methods, such as anaerobic digestion and transesterification, further enhance flexibility in handling diverse feedstocks and adapting outputs to market demands. Coupling algal cultivation with wastewater treatment provides additional sustainability and cost advantages. Nutrient-rich effluents serve as low-cost growth media, while simultaneous pollutant removal reduces waste disposal burdens [334,335,336]. This closed-loop approach aligns with circular economy principles, lowering operational costs and enabling deployment in municipal and agricultural contexts.

10.2. Digital Optimization and AI-Driven Strain Development

Artificial intelligence (AI) and machine learning (ML) applications are emerging as transformative tools for optimizing algal cultivation and bioplastic production. AI optimization, successfully reducing bacterial fermentation costs by 15–25%, could theoretically achieve similar improvements in algal systems [337]. Predictive AI models, integrated with smart biorefinery control systems, have demonstrated biomass yield increases of 30–50%, along with improved nutrient efficiency and reduced energy consumption [338,339,340,341]. These systems enable real-time monitoring and adaptive control of environmental parameters, stabilizing productivity even under fluctuating external conditions. Incorporating AI and ML into production frameworks will be critical to scaling high-output, resilient algal bioprocesses for industrial applications.

10.3. Collaborative Ecosystem for Commercialization

Transitioning algal bioplastics from laboratory research to market adoption requires a coordinated ecosystem linking government, industry, and academia. Governments can accelerate commercialization through policy incentives, carbon credit schemes, and streamlined regulatory pathways; industries can pilot and scale promising technologies; and academia can provide targeted R&D addressing both performance and market demands [113,342,343,344]. Strategic partnerships, combined with public awareness campaigns, will be essential to build consumer trust and strengthen market penetration, ensuring algal bioplastics compete effectively with conventional materials in diverse sectors.

11. Conclusions

11.1. Synthesis of Key Findings

Algal bioplastics represent a viable and environmentally responsible alternative to petroleum-based polymers, offering benefits such as reduced greenhouse gas emissions, renewable feedstock availability, and potential integration within circular bioeconomy models. Current research demonstrates that advances in cultivation systems, strain improvement, and processing technologies have significantly improved production efficiency and material quality. However, widespread adoption remains constrained by economic and logistical challenges, including high production costs, scalability limitations, and the need for standardized regulatory frameworks. Integrated biorefinery approaches, strategic government–industry–academia collaborations, and continued innovation in process optimization are critical to overcoming these barriers. While this review includes both proven algal applications and theoretical extrapolations from microbial systems, the trajectory clearly indicates that algal bioplastics will transition from concept to commercial reality as the identified technical barriers are addressed. With sustained investment in research, infrastructure, and supportive policy mechanisms, algal bioplastics could transition from niche applications to mainstream markets, contributing substantially to global sustainability goals.

Key Takeaways

Sustainability Potential: Algal bioplastics can reduce environmental impacts compared to petroleum-based plastics.

Technological Progress: Advances in cultivation, strain optimization, and processing are improving efficiency and quality.

Challenges to Scale-Up: High production costs and regulatory gaps remain key barriers.

Path Forward: Biorefinery integration, collaborative partnerships, and supportive policy are essential for market expansion.

11.2. Critical Limitations

This review identifies several critical barriers that must be acknowledged:

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Economic: Current production costs ($4–10/kg) exceed petroplastics.

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Technical: Genetic instability reduces yields by 30–50% over 20 generations.

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Scalability: No facility exceeds 1000 tonnes/year production.

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Regulatory: Absence of international standards for marine biodegradability.

11.3. Prioritized Research Roadmap

Based on this analysis, we propose the following priorities:

• Immediate (1–2 years): Standardize testing protocols and improve genetic stability.
• Short-term (3–5 years): Demonstrate stable pilot-scale production (>100 tonnes/year).
• Medium-term (5–10 years): Achieve cost parity through integrated biorefineries.
• Long-term (10+ years): Establish circular economy infrastructure.