Microalgae-Based Technologies for Wastewater Treatment, Resource Recovery, and High-Value Bioproducts

Topic Information

Dear Colleagues,

Microalgae-based technologies are gaining increasing attention as sustainable solutions to global challenges in wastewater treatment, resource recovery, CO₂ mitigation, and the development of value-added bioproducts. Microalgae exhibit exceptional capabilities in nutrient removal, CO₂ fixation, the biosorption of pollutants, and the biotransformation of organic wastes. Moreover, their biomass can be further valorized into biofuels, feed additives, bioactive compounds, pigments, polysaccharides, and other high-value products.

This Topic aims to bring together cutting-edge research on microalgae–wastewater systems, spanning fundamental mechanisms, rational design and engineering of algal strains, bioprocess engineering, and industrial applications. We welcome submissions that explore innovative technologies for water pollution control, nutrient recovery, algal–bacterial interactions, and integrated biorefineries, as well as interdisciplinary approaches linking environmental engineering, biotechnology, and marine bioresources.

Topics of interest include, but are not limited to, the following:

• Microalgae-based wastewater treatment (nutrient removal, ammonia/organic-rich wastewater treatment, biogas slurry treatment, pollutant degradation);
• Algal–bacterial consortia systems;
• Biological nitrogen and carbon removal processes (autotrophic nitrogen removal, anaerobic systems, carbon capture using microalgae);
• Resource recovery and circular bioeconomy (valorization of waste streams into lipids, H₂, pigments, polysaccharides, proteins, biofertilizers);
• Heterotrophic and mixotrophic microalgae cultivation;
• Metabolic regulation and synthetic biology for improved bioproduct accumulation;
• Bioprocess engineering and scale-up (photobioreactors, outdoor cultivation, bioreactor design, magnetic harvesting, co-culture strategies);
• Marine microalgae and marine bioactive compounds (functional ingredients, antioxidant/antitumor activities, bioactive polysaccharides);
• Life-cycle assessment, techno-economic analysis, and large-scale demonstration practices.

We particularly encourage contributions demonstrating pilot- or engineering-scale applications, innovative process integration, and strategies that advance microalgae-based technologies toward practical deployment.

We believe that this Topic will serve as an inspiring platform to promote interdisciplinary collaboration and accelerate the transition toward sustainable water treatment and resource recovery using microalgae.

Dr. Yuansheng Hu
Prof. Dr. Hui Chen
Prof. Dr. Liqin Sun
Dr. Zhongliang Sun
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.9	6.1	2011	15 Days	CHF 2400	Submit
BioTech biotech	3.6	5.6	2012	20.7 Days	CHF 1800	Submit
Chemistry chemistry	2.6	4.4	2019	13 Days	CHF 1800	Submit
Foods foods	6.0	10.3	2012	14.8 Days	CHF 2900	Submit
Marine Drugs marinedrugs	5.7	11.6	2003	14.2 Days	CHF 2900	Submit
Microorganisms microorganisms	4.7	8.2	2013	16.5 Days	CHF 2700	Submit
Water water	3.5	6.7	2009	17.7 Days	CHF 2600	Submit

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Published Papers (5 papers)

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All Marine Drugs Water Microorganisms Applied Sciences BioTech Foods Chemistry

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26 pages, 374 KB  

Open AccessReview

Microalgae as Novel Food Resources: Technological Breakthroughs, Application Bottlenecks, and Future Pathways

by Xiaomei Zhang, Weixian Chen and Hui Chen

Foods 2026, 15(12), 2241; https://doi.org/10.3390/foods15122241 - 22 Jun 2026

Viewed by 489

Abstract

Global population growth and the demand for sustainable food systems have pushed microalgae into the spotlight as promising novel food resources. They are rich in protein, omega-3 fatty acids, and bioactive pigments including astaxanthin and phycocyanin. Unlike conventional farming, microalgae cultivation can be [...] Read more.

Global population growth and the demand for sustainable food systems have pushed microalgae into the spotlight as promising novel food resources. They are rich in protein, omega-3 fatty acids, and bioactive pigments including astaxanthin and phycocyanin. Unlike conventional farming, microalgae cultivation can be conducted on non-arable land and may reduce direct competition with conventional food crops for land resources, depending on the production system used. Regulatory progress in China, the European Union (EU), and the United States has resulted in the authorization or approval of several microalgal species and microalgae-derived ingredients for specific food and nutritional applications, including dietary supplements, infant nutrition products, and alternative protein ingredients. Despite these advances, broader commercial adoption remains constrained by several challenges, such as off-flavors and the dark green color, high production costs from closed photobioreactors and energy-intensive downstream purification, fragmented regulatory frameworks across jurisdictions and limited long-term data on bioavailability, allergenicity, safety, and dose–response relationships for some emerging strains. This review focuses on microalgae as novel food resources, covering regulatory approvals, strain selection, high-value utilization, and market translation, synthesizes evidence on nutritional evaluation, application scenarios, and global regulatory differences, analyzes key bottlenecks, and proposes pathways to bridge fundamental research with industrial practice. It also highlights unresolved knowledge gaps to guide future research and policy. Full article

(This article belongs to the Topic Microalgae-Based Technologies for Wastewater Treatment, Resource Recovery, and High-Value Bioproducts)

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27 pages, 3580 KB  

Open AccessArticle

Use of an Alkaline Wastewater Stream to Increase the Initial pH of Whey and Recover a Microbial Biomass with High Protein Content

by Marisol Pérez-Cortés, Janet A. Gutiérrez-Uribe and Mariana Franco-Morgado

Foods 2026, 15(11), 2022; https://doi.org/10.3390/foods15112022 - 4 Jun 2026

Viewed by 372

Abstract

Sweet whey (SW) and nejayote (NE), two agro-industrial wastewaters generated in Mexico, were evaluated as growth media for the cultivation of an alkaliphilic microalgae–cyanobacteria consortium (AMC) which has been reported to contain Nannochloropsis sp. and Pseudanabaena sp. at different initial pH (8, 9, [...] Read more.

Sweet whey (SW) and nejayote (NE), two agro-industrial wastewaters generated in Mexico, were evaluated as growth media for the cultivation of an alkaliphilic microalgae–cyanobacteria consortium (AMC) which has been reported to contain Nannochloropsis sp. and Pseudanabaena sp. at different initial pH (8, 9, and 10). Phototrophic-mixotrophic cultivation was conducted for 14 d using nejayote with biomass (NEB), sweet whey with biomass (SWB), and a mixture of nejayote and sweet whey with biomass (NESWB) to assess organic matter removal, biomass formation, and metabolite dynamics. The highest chemical oxygen demand (COD) removal was observed in NEB at pH 8, reaching 91.66% and a final COD of 1.04 g L⁻¹. Initial pH values of 9 and 10 maintained alkaline conditions through phototrophic–mixotrophic cultivation, indicating stable biological pH regulation associated with photosynthetic activity. NESWB promoted higher biomass production, particularly at pH 9, suggesting enhanced conversion of organic matter into suspended solids. Moreover, the highest intracellular protein content (30.50 ± 0.90% dry weight) was obtained in NESWB at pH 10, supported by FTIR and SDS-PAGE analyses that indicated changes in protein-related spectral features and band profiles. Biomass reached 4.77 ± 0.80 g L⁻¹ and COD decreased from 14.60 ± 0.70 to 4.18 ± 0.31 g L⁻¹. These results demonstrate that the integration of sweet whey and nejayote under alkaline conditions enables simultaneous wastewater treatment and production of protein-rich biomass, highlighting a sustainable strategy for agro-industrial residue valorization. Full article

(This article belongs to the Topic Microalgae-Based Technologies for Wastewater Treatment, Resource Recovery, and High-Value Bioproducts)

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21 pages, 2967 KB  

Open AccessArticle

5-Aminolevulinic Acid Drives Coordinated Astaxanthin and Lipid Accumulation in Green Alga Chromochloris zofingiensis

by Jinrui Gao, Zhongliang Sun, Bin Liu, Yu Zhang and Liqin Sun

Foods 2026, 15(10), 1768; https://doi.org/10.3390/foods15101768 - 17 May 2026

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Abstract

Chromochloris zofingiensis, a photosynthetic microalga, has attracted considerable attention due to its ability to simultaneously accumulate lipids and astaxanthin. However, the induction of lipid and secondary metabolite biosynthesis by abiotic stress is typically accompanied by growth inhibition, resulting in a trade-off between [...] Read more.

Chromochloris zofingiensis, a photosynthetic microalga, has attracted considerable attention due to its ability to simultaneously accumulate lipids and astaxanthin. However, the induction of lipid and secondary metabolite biosynthesis by abiotic stress is typically accompanied by growth inhibition, resulting in a trade-off between metabolite accumulation and biomass production. In recent years, phytohormones have emerged as an effective strategy for regulating microalgal metabolism, owing to their high specificity and low effective dosage. In this study, 5-aminolevulinic acid (5-ALA) was applied under nitrogen-deficient conditions, and its effects on growth, photosynthesis, lipid metabolism, and carotenoid biosynthesis were systematically evaluated through integrated physiological, biochemical, and transcriptomic analyses. The results showed that 5-ALA had no significant effect on biomass accumulation or photosynthetic performance. However, at 2 μM, 5-ALA exhibited the strongest promotive effect on lipid and astaxanthin accumulation, with total fatty acids (TFA) and triacylglycerol (TAG) contents increasing by 13.3% and 25.7%, respectively, and total carotenoids and astaxanthin contents increasing by 15.6% and 17.2%, respectively. Under semi-continuous cultivation, TAG and astaxanthin productivities were enhanced by 13.9% and 22.9%, reaching 164 mg L⁻¹ d⁻¹ and 2.15 mg L⁻¹ d⁻¹, respectively. Transcriptomic analysis revealed that 5-ALA induced only limited transcriptional changes but enhanced glycolysis, central carbon metabolism, and nitrogen recycling, thereby increasing the supply of carbon precursors and energy. Notably, no significant transcriptional changes were observed in the carotenoid biosynthesis pathway, indicating that the enhanced accumulation of total carotenoids and astaxanthin was likely driven by increased metabolic flux. In terms of lipid metabolism, the upregulation of pathways involved in the conversion of membrane lipids into TAG, together with the downregulation of TAG degradation pathways and enhanced carbon flux, collectively promoted TAG accumulation. Overall, this study demonstrates that supplementation with 2 μM 5-ALA provides a practical and cost-effective strategy for the efficient co-production of lipids and astaxanthin in C. zofingiensis. Full article

(This article belongs to the Topic Microalgae-Based Technologies for Wastewater Treatment, Resource Recovery, and High-Value Bioproducts)

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28 pages, 3001 KB  

Open AccessReview

Engineering and Biological Mechanisms of Microalgal CO₂ Fixation: A Review from Molecular Regulation to System Optimization

by Zhongliang Sun, Weixian Chen, Yu Xie, Shoukai Guo, Liqin Sun and Qiang Wang

Microorganisms 2026, 14(5), 999; https://doi.org/10.3390/microorganisms14050999 - 29 Apr 2026

Viewed by 888

Abstract

Microalgae are among the most efficient photosynthetic organisms on Earth, and their capacity for CO₂ fixation directly links the global carbon cycle with green energy conversion, positioning them as strategic biological platforms for achieving carbon neutrality. This review provides a comprehensive and [...] Read more.

Microalgae are among the most efficient photosynthetic organisms on Earth, and their capacity for CO₂ fixation directly links the global carbon cycle with green energy conversion, positioning them as strategic biological platforms for achieving carbon neutrality. This review provides a comprehensive and multiscale synthesis of the engineering and biological mechanisms underlying microalgal CO₂ fixation, integrating perspectives from gas–liquid mass transfer, CO₂ assimilation pathways, key enzymatic systems, metabolic regulation, and environmental control. From an engineering standpoint, we analyze the limitations governing CO₂ transfer from the gas phase to the aqueous phase and critically evaluate intensification strategies aimed at enhancing inorganic carbon availability in cultivation systems. At the biological and biochemical levels, we dissect carbon concentrating mechanisms (CCMs), including C₄-like pathways, and elucidate the structural organization, regulatory properties, and functional coordination of Rubisco and carbonic anhydrase systems. Particular emphasis is placed on the coupling between enzyme-level regulation and metabolic flux redistribution, supported by insights from metabolic flux analysis and systems-level modeling, to establish theoretical and engineering foundations for improving carboxylation efficiency. Finally, we propose an integrated roadmap for the future development of microalgal CO₂ fixation technologies, highlighting the convergence of synthetic biology, artificial intelligence, and systems engineering to achieve end-to-end optimization from molecular mechanisms to reactor-scale performance, while enabling the valorization of waste gas streams and circular carbon utilization. This review aims to provide a coherent theoretical framework and forward looking perspective for the development of efficient, intelligent, and sustainable microalgal CO₂ fixation systems. Full article

(This article belongs to the Topic Microalgae-Based Technologies for Wastewater Treatment, Resource Recovery, and High-Value Bioproducts)

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16 pages, 2115 KB  

Open AccessArticle

Effects of Cultivation Conditions and Bean Curd (Tofu) Wastewater Application on ALA Accumulation in Chlorella sp. L166 and Its Mutant C-12

by Xiaoxuan Zhou, Shuo Wei, Xuechao Zheng and Ye Chen

Foods 2026, 15(9), 1524; https://doi.org/10.3390/foods15091524 - 28 Apr 2026

Viewed by 354

Abstract

Alpha-linolenic acid (ALA) is an essential omega-3 fatty acid and a vital component in food applications. In this study, we investigated a range of physicochemical culture conditions—including pH, temperature, and carbon source—to evaluate biomass and ALA accumulation in Chlorella sp. L166 and its [...] Read more.

Alpha-linolenic acid (ALA) is an essential omega-3 fatty acid and a vital component in food applications. In this study, we investigated a range of physicochemical culture conditions—including pH, temperature, and carbon source—to evaluate biomass and ALA accumulation in Chlorella sp. L166 and its mutant, C-12. The study aimed to identify favorable culture conditions and evaluate the feasibility of using diluted bean curd (tofu) wastewater as a low-cost medium. Under mixotrophic cultivation, ALA content was determined via GC-MS, and the removal efficiencies of total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) were simultaneously monitored. The results showed that L166 achieved its highest ALA accumulation at pH 6.0 and 23 °C with maltose. C-12 exhibited appropriate ALA accumulation at pH 7.0 and 23 °C with maltose and reached its maximum biomass at pH 8.0 and 25 °C with glucose. After 8 days of cultivation in threefold-diluted tofu wastewater, C-12’s ALA content reached 6.1 mg/g, significantly higher than that observed in BG11 medium. Meanwhile, both strains removed 81.2–83.2% of TN, 35.7–36.0% of TP, and 42.6–43.5% of COD. This study provides preliminary data on the effects of culture conditions on microalgal ALA production, highlighting the potential for future practical applications of C-12. Full article

(This article belongs to the Topic Microalgae-Based Technologies for Wastewater Treatment, Resource Recovery, and High-Value Bioproducts)

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