Search Results (69)

Microalgal lipids are promising sustainable feedstocks for high-value functional ingredients. However, the influence of cultivation-driven lipid composition on enzymatic conversion remains poorly understood. This study integrated cultivation strategy and enzymatic upgrading to tailor Neochloris oleoabundans lipids for mono- and diacylglycerol (MAG and DAG) production. Heterotrophic cultivation achieved a maximum dry biomass concentration of 2.78 ± 0.14 g L⁻¹, whereas autotrophic cultivation reached 0.39 ± 0.01 g L⁻¹, confirming the superior biomass productivity of heterotrophic metabolism. Lipid fractions obtained under both trophic conditions were characterized and subjected to glycerolysis catalyzed by Novozym 435 under a 5:1 glycerol-to-oil ratio for 16 h. Heterotrophic oils, characterized by triacylglycerol-rich and low-free fatty acid (FFA) profiles, achieved higher MAG + DAG conversion (45%), while autotrophic oils reached 43% conversion despite elevated FFAs and polar lipids. The presence of FFAs, pigments, and phospholipids in non-refined microalgal oils influenced catalytic behavior, reducing conversion efficiency and favoring competing esterification and hydrolysis pathways. These findings demonstrate that substrate purity, acylglycerol distribution, and cultivation-specific lipid architecture strongly affect lipase performance, highlighting oil refining and cultivation optimization as key strategies for improving sustainable MAG and DAG production. Full article

Microalgae represent a promising alternative as biofertilizers and biostimulants, providing essential nutrients and bioactive compounds that support plant growth. In this study, a screening of seven microalgal species—including Arthrospira platensis, Nannochloris sp., Chlorella sp., Chlorella vulgaris, Acutodesmus obliquus, Parachlorella kessleri, Coelastrella vacuolata—and one isolated mixed culture was conducted to evaluate their potential as biostimulants and biofertilizers under autotrophic cultivation conditions. Whole cultures and corresponding supernatants were directly applied, without any pretreatment, reducing potential processing costs. Their biostimulant activity was evaluated through multiple bioassays, including germination index and auxin- and cytokinin-like responses, while nitrogen, phosphorus, and potassium content was analyzed to assess biofertilizer potential. The results revealed that biostimulant effects were strongly influenced by species, concentration, and sample fraction. Chlorella species consistently showed high performance across assays, combining strong germination and rooting responses with high nitrogen content (8.2–8.8% w/w), while A. platensis and Nannochloris sp. showed inhibitory effects in many cases. Overall, under the cultivation and application conditions tested, C. vulgaris, mixed culture, and A. obliquus are identified as promising candidates for combined biostimulant and biofertilizer applications. This study is a primary step in identifying the most promising species as an alternative to synthetic fertilizers, enabling further optimization towards more sustainable agricultural practices. Full article

This study set out to cultivate and isolate hydrogen-oxidising bacteria (HOB) for microbial protein production under a specific culture strategy with a particular focus on assessing the influence of different environmental sources on enrichment culture and strain diversity. Therefore, HOB were enriched from samples collected from various freshwater lakes and streams, and novel strains were subsequently isolated from these cultures. The enrichment procedure revealed significant shifts in community compositions, which were mainly driven by changes in the relative abundance of genera affiliated to Pseudomonadota and Bacteroidota. Sample-specific variations were observed in the communities of the inocula, reflecting distinct community structures associated with distinct ecological functions. The most common autotrophic HOB, Hydrogenophaga, proliferated in some of the cultures. However, several genera, such as Acinetobacter and Klebsiella that have not been previously recognised with hydrogen-oxidation characteristics, were also enriched, suggesting potential novel contributors to HOB communities. Full article

Members of the class Campylobacteria are microaerophilic bacteria widely distributed across diverse environments and are abundant in hydrothermal systems. However, cultivated representatives, particularly from shallow-water vents, remain limited. Here, we investigated the genomic diversity and environmental adaptation of the genus Sulfurospirillum. Phylogenomic analysis revealed a clear separation between terrestrial and marine clades, with relatively few cultured representatives in the marine lineage. Strain 1307, isolated from shallow-water hydrothermal vents, expands the genomic representation of this underexplored clade. Pan-genome analyses based on complete genomes revealed an open pan-genome, indicating ongoing diversification of genus Sulfurospirillum. Further comparison between hydrothermal vent (HTV) and non-HTV lineages identified distinct adaptive features. Vent-associated strains are enriched in genes involved in sulfur metabolism, carbon fixation, the glycine cleavage system (GCS), and the biosynthesis of key cofactors (spermidine, thiamine, lipoate, and heme), reflecting metabolic adaptation to hydrothermal environments. Beyond well-established processes such as sulfur metabolism and autotrophic carbon fixation, the widespread presence of the GCS in vent-associated lineages suggests its potential role as an auxiliary carbon fixation pathway under anaerobic conditions. Overall, this study expands the phylogenetic and genomic diversity of Sulfurospirillum and offers new insights into the mechanisms underlying environmental adaptation and niche differentiation in vent-associated Campylobacteria. Full article

Background/Objectives: Natural polysaccharides have many bio-pharmacological effects, which make them compounds with potential in healthcare. Limnospira platensis (Spirulina), a well-known blue–green cyanobacterium with relevance in the market of nutraceuticals, produces polysaccharides with recognized antioxidant and anti-inflammatory activities. Noteworthy, the growth of the cyanobacterium biomass may be obtained in a more sustainable manner under mixotrophic conditions. In the present study, we compared the antioxidant and anti-inflammatory effects of polysaccharide-enriched extracts from the cyanobacterium cultured under autotrophism (Auto−P extract) or mixotrophism (Mixo−P extract); this latter was realized using medium added with brewery wastewater (BWW). Methods and Results: Non-cellular investigation showed a better antioxidant profile for Mixo−P extract in the OH radical scavenging assay and a similar activity between the extracts in ABTS and ferrous chelation assays. The antioxidant protective activity of L. platensis extracts investigated on HaCat cells in the range of 0.3–10 μg/mL (not cytotoxic concentrations), against hydrogen peroxide (H₂O₂, 600 μM)-induced damage, revealed a similar activity by the two extracts. When tested against the inflammatory stimuli with lipopolysaccharide (LPS, 10 μg/mL) or tumor necrosis factor-α (TNF-α, 10 ng/mL), both Auto−P and Mixo−P showed an ability to prevent the effects of the inflammatory agents on cell viability and on interleukin-1β (IL-1β) and interleukin-6 (IL-6) release, with a slightly greater potency by Mixo−P extract. Conclusions: In conclusion, our data suggest the possible use of L. platensis polysaccharide-enriched extracts in biological-made pharmaceuticals for skin disorders or in cosmeceuticals. In addition, this study demonstrates that mixotrophic cultivation of L. platensis may be an alternative and sustainable way for biotechnological applications of the cyanobacterium biomass. Full article

Research on heterotrophic bioflocs is extensive, whereas investigations into autotrophic bioflocs remain limited. This study established an in situ autotrophic biofloc (ABF) system for intensive Pacific white shrimp (Penaeus vannamei) farming, aiming for zero water exchange and optimized water quality. A 120-day indoor experiment tested three stocking densities (300 (T1), 250 (T2), and 200 shrimp per m³ (T3)) with no water exchange. Water quality was monitored every two days, and bacterial communities were analyzed on days 10 and 70. The results indicated that ABF maturation was achieved by day 70 across all treatments, marked by three key indicators: (1) synchronous declines in nitrite and nitrate concentrations; (2) concurrent decreases in pH and total alkalinity approaching maturation; and (3) sustained high nitrogen removal efficiency (nitrite < 0.7 mg/L, ammonia < 0.6 mg/L). All density groups displayed similar patterns in both water quality dynamics and microbial community evolution. Bacterial analysis revealed that dominant genera such as Ruegeria, Bacillus, Muricauda, SM1A02, and Nitrospira played critical roles in toxic nitrogen removal, while pathogenic Klebsiella and Vibrio significantly decreased post-maturation. Heterotrophic nitrification and aerobic denitrification microorganisms (HNADMs) were identified as potentially responsible for nitrite accumulation. Nitrite accumulation was found in all groups. T2 and T3 achieved satisfactory breeding performance despite pre-maturation nitrate peaks exceeding 40 mg/L, whereas T1 suffered a low survival rate (27.47%) due to severe nitrite accumulation (>50 mg/L). A biofloc volume (BFV) of 4–8 mL/L effectively managed daily feed inputs of 75–110 g/m³. These findings lay a theoretical and technical foundation for the application of in situ ABF cultivation in intensive farming and enhance the sustainability of aquaculture. Full article

Microcystis aeruginosa formed in natural water bodies grow in aggregate particles, while Microcystis aeruginosa commonly used in scientific research grow in a single-celled discrete state during cultivation. To elucidate the factors and mechanisms of Microcystis aeruginosa entering the “cell-aggregate” survival state in the natural environment, we focused on studying the influence of biological factors in their living environment (coexisting bacteria) on the aggregation behavior and growth characteristics of Microcystis aeruginosa. The bacterial strain A20, which can promote the aggregative behavior of Microcystis aeruginosa, was isolated from the water of Taihu Lake, where a cyanobacterial bloom broke out. A20 was identified as Priestia megaterium. Results showed that A20 could significantly drive Microcystis aeruginosa to form sac-like aggregate structures and promote the increase of aggregate particle size from 3–7 μm to 180 μm. The coexistence of bacteria and algae exhibited a dynamic stage adaptation strategy, with A20 promoting the transition of Microcystis aeruginosa from “high-chlorophyll, low-photochemical efficiency growth and proliferation” to “stable survival and maintenance of chlorophyll and photochemical efficiency in fluctuating changes” adaptation strategies. The coexistence of bacteria and algae significantly intensified the release of humic acid-like, fulvic acid-like, and protein-like substances from Microcystis aeruginosa, with the most significant increase in small-molecule fulvic acid-like substances. This is probably related to the endogenous metabolic stress response of Microcystis aeruginosa during A20 invasion, as well as the utilization and transformation of autotrophic Microcystis aeruginosa metabolites by heterotrophic bacteria A20. This study contributes to the study of microbial interactions underlying bloom outbreaks and can be useful for developing community-targeted algal control technologies. Full article

The agro-industrial sector in Indonesia produces significant amounts of nutrient-rich waste and wastewater, which pose environmental risks but also present opportunities for valorization within a circular bioeconomy. Microalgae provide a promising solution for transforming these wastewaters into valuable products such as biomass for bioenergy, biofertilizers, or pigments, all while helping to remediate pollutants. This review synthesizes current knowledge on the use of major Indonesian agro-industrial effluents, specifically palm oil mill effluent (POME), byproducts from cassava and sugarcane, and soybean residues, as substrates for microalgal biomass production and cultivation. Furthermore, various cultivation strategies are summarized, including autotrophic, heterotrophic, and mixotrophic methods, as well as the use of open ponds, photobioreactors, and hybrid systems. These cultivation processes influence biomass yield, metabolite production, and nutrient removal. Reported studies indicate high removal efficiencies for organic loads, nitrogen, and phosphorus, along with considerable production of lipids, proteins, pigments, and biofuels. Yet, effluent pretreatment, concerns about heavy metal and pathogen contamination, high downstream processing costs, and biosafety issues remains as challenges. Nonetheless, the application of microalgal cultivation into Indonesia’s agro-industrial wastes treatment can provide the dual benefits of waste mitigation and resource recovery, helping to advance climate goals and promote rural development. Full article

Anaerobic digestion (AD) produces renewable energy but releases biogenic CO₂ and generates digestate requiring management. This paper evaluates four emerging pathways for CO₂ capture and reuse in AD systems: (1) in situ CO₂ conversion to CH₄ via microbial electrolysis cells (MECs), (2) hydrogenotrophic CO₂ methanation using green hydrogen, (3) enzymatic CO₂ capture coupled with autotrophic algae cultivation, and (4) digestate pyrolysis with syngas biomethanation. Each pathway is assessed in terms of technical feasibility, biocatalyst performance, system configuration, and key implementation challenges. Integrated scenarios demonstrate up to 98% CO₂ emission reduction, substantial bioenergy yield improvements, and enhanced nutrient and biomass recovery compared to conventional AD. MEC-based and hydrogenotrophic pathways show the highest energy efficiency, while algae-based systems provide added bioproduct valorization. The remaining limitations include cost, process integration, and scale-up. The study defines development priorities to advance zero-emission AD technologies for the agri-food and waste management sectors. Full article

Chlorella is a valuable object of biotechnology with high productivity of biomass and metabolites. The use of Chlorella for CO₂ binding in autotrophic metabolism is also discussed. Various types of stress are used to increase the yield of valuable metabolites. One of the effective approaches may be dark stress. However, there is insufficient data to fully understand the effect of dark stress on productivity, biochemical parameters, the antioxidant system, and the rate of CO₂ fixation by Chlorella during the transfer from autotrophic culture to aphotic conditions. To study these processes, we used two-step cultivation. In the second step, the biomass was grown for 96 h on a BBM medium under standard lighting and in aphotic conditions. According to the results of the study, the metabolic systems of the studied strain of Chlorella sp. CAMU G–145 specifically react to cultivation under aphotic conditions. The greatest response was found in lipid–protein metabolism and the antioxidant defense system, which determines an increase in the overall antioxidant status of cells. At the same time, productivity, CO₂ absorption characteristics, and pigment composition of the photosynthetic system did not change after 96 h of darkening. In general, this approach is a promising strategy for increasing biotechnological productions efficiency. Full article

The aim of the study was to evaluate the feasibility of using exhaust gases as a CO₂ source in the cultivation of Tetraselmis subcordiformis microalgae for biomass and hydrogen production. It was shown that the growth rate of T. subcordiformis biomass and its biochemical composition depended on the CO₂ source. The highest growth rate of 286 ± 15 mgVS/L-d and a final biomass concentration of 2710 ± 180 mgVS/L were achieved in the variant where exhaust gases from a coal and biomass supplementary combustion plant were the CO₂ source (V2). The highest CO₂ reduction efficiency of 90.3 ± 3.2% was achieved in the case where waste gases from biogas combustion were the CO₂ source (V1). In V2, the highest CO₂ utilization efficiency was achieved (CO₂UE = 46.7 ± 2.4%). Analyzing the biomass composition confirmed differences in total carbon content (TC) and polysaccharide fraction. The highest H₂ production efficiency and rate, which were 70.9 ± 2.7 mL/gVS and 2.27 ± 0.08 mL/gVS·h, respectively, were obtained in V2. The results obtained indicate the possibility of integrating fuel combustion processes with the cultivation of T. subcordiformis and photobiological H₂ production, which is a promising solution in the context of climate neutrality and the implementation of circular economy postulates. This approach demonstrates a sustainable strategy for linking industrial CO₂ emissions with the production of renewable biohydrogen and thus contributes to climate protection and the promotion of circular economy concepts. Full article

There is an increasing industrial demand for sustainable resources for lipid-based biofuels and platform chemical production. A promising, CO₂-efficient resource is autotrophically cultivated microalgae, either for direct single-cell oil (SCO) production or as a biomass substrate for fermentative SCO production via organisms like yeasts. Regarding the latter, chemical biomass hydrolysis typically results in high sugar yield and high salt concentrations due to the required neutralization prior to fermentation. In contrast, enzymatic hydrolysis is often lacking in mass efficiency. In this study, the enzymatic hydrolysis of both nutrient-replete and lipid-rich autotrophic Microchloropsis salina biomass was optimized, testing different pre-treatments and enzyme activities. Hereby, the protease treatment to weaken the cell wall integrity and the dosing of the Cellic CTec3 was identified to have the highest effect on hydrolysis efficiency. Sugar yields of 63% (nutrient-replete) and almost 100% (lipid-rich) could be achieved. The process was successfully scaled-up in mini bioreactors at a 250 mL scale. The resulting hydrolysate of the lipid-rich biomass was tested as a substrate of the oleaginous yeast Cutaneotrichosporon oleaginosus in a consumption-based acetic acid fed-batch setup. It outperformed both the model substrate and the glucose control, demonstrating the high potential of the hydrolysate as feedstock for yeast oil production. The presented sequential and circular SCO-producing value chain highlights the potential for mass- and space–time-efficient biofuel production, combining the autotrophic cultivation of oleaginous algae with decoupled yeast oil fermentation for the first time. Full article

Syngas fermentation in combination with chain elongation offers great promise for sustainable medium-chain fatty acid production. While immobilization has proven effective for stabilizing monocultures of C. kluyveri for chain elongation, its applicability to co-cultures involving C. carboxidivorans for simultaneous syngas fermentation remains unexplored. This study investigates the physiological compatibility of C. carboxidivorans with agar-based hydrogel immobilization and its co-cultivation potential with C. kluyveri in a synthetic dual-layer biofilm reactor. First, we conducted autotrophic batch fermentations using suspended and immobilized cells, proving metabolic activity similar for both. Applying different sulfur feeding rates, experiments showed best ethanol formation with C. carboxidivorans at increased sulfur feeding, enabling better conditions for chain elongation with C. kluyveri. In the synthetic dual-layer biofilm reactor, with the C. carboxidivorans biofilm in contact with the CO-containing gas phase above the C. kluyveri biofilm, the formation of 1-butyrate and 1-hexanoate was observed with product formation rates of 0.46 g L⁻¹ d⁻¹ 1-butyrate, and 0.91 g L⁻¹ d⁻¹ 1-hexanoate, respectively. The formation rate of 1-hexanoate in the dual-layer biofilm reactor was approximately 7.6 times higher than that reported with suspended cells in a stirred tank bioreactor. Spatial analysis revealed species-specific migration behavior and confirmed that C. carboxidivorans reduced local CO concentrations, improving the environment for C. kluyveri. Full article

In this paper, the production of biomass, pigments, lipids, and carbohydrates and the elimination of ammonium and orthophosphate by the microalgae Chlorella vulgaris, grown in synthetic wastewater (SWW), were studied under different light intensities (3000–10,000 lux), pH (7.5–9.5) and daily illumination time (8–16 h). The best conditions for the autotrophic culture of microalgae were predicted using response surface methodology (RSM). The results showed that the adaptation of the microalgae for this nutrient source was effective. The best conditions for the cultivation of Chlorella vulgaris in SWW were 8.44 pH and a light intensity of 8433 lux in the daily illumination time of 16 h. Under optimal conditions, the production of microalgal biomass, chlorophyll-a, chlorophyll-b, carotenoids, lipids and carbohydrates was 0.534 g/L, 7.46 mg/mL, 3.53 mg/mL, 2.01 mg/mL, 21.40% and 28.46%, respectively. The removal efficiencies of ammonium and orthophosphate from SWW were 97.66% and 58.78% in autotrophic cultures. This investigation introduces a new aspect by verifying the optimized cultivation conditions with real municipal wastewater, indicating that the procedure could be utilized for sustainable production of bioproducts and efficient treatment of municipal wastewater. Full article

Biomass-derived growth stimulants are widely recognized as green and economical solutions that can significantly enhance microalgae culture efficiency and optimize the biomanufacturing process of target products. In this paper, we investigated the effect of ethanol synergized with guaiacol (GA) on biomass and β-1,3 glucan accumulation in edible microalgae, namely Euglena gracilis. The ethanol-induced mixotrophic mode significantly increased biomass and paramylon production by 12.68 and 6.43 times, respectively, compared to the autotrophic control group. GA further exerted toxic excitatory effects (hormesis) on top of ethanol mixotrophic nutrition. At the optimal concentration of 10 mg·L⁻¹ GA, chlorophyll a, carotenoids, and paramylon production increased by 8.96%, 11.75%, and 16.67%, respectively, compared to the ethanol-treated group. However, at higher concentrations, the biomass and paramylon yield decreased significantly. This study not only establishes an effective combinatorial strategy for enhancing paramylon biosynthesis but also provides novel insights into the hormesis mechanism of phenolic compounds in microalgae cultivation. The developed approach demonstrates promising potential for sustainable production of high-value algal metabolites while reducing cultivation costs, which could significantly advance the commercialization of microalgae-based biorefineries in food and pharmaceutical industries. Full article