Microalgae are microscopic, usually unicellular or filamentous photosynthetic organisms that thrive in diverse and often harsh aquatic habitats. Compared with terrestrial crops, they offer striking advantages: short multiplication times, no need for arable land, and dry biomass productivity exceeding 100 tonnes per hectare per year. They convert sunlight into chemical energy with an efficiency of around 10 percent, far above the roughly 4.6 percent maximum estimated for C3 terrestrial plants, and they are highly efficient at fixing carbon dioxide. Wild-type algae species have been estimated to reach a maximum photosynthetic efficiency of 8.3 percent, and outdoor cultures supplemented with carbon dioxide have reported annual average efficiencies above 5 percent. Because microalgae contain more chlorophyll per unit area than land plants, they can remove 10 to 50 times more CO2, making them a compelling candidate for carbon capture and storage with high photosynthetic rates, rapid growth, superior environmental adaptation and low operating costs.

The global algae industry has already expanded dramatically, surging from 0.56 million tonnes in 1950 to 35.82 million tonnes in 2019, with more than 97 percent of production coming from Asia. China leads with 57 percent of global output, followed by Indonesia at 27 percent, South Korea at 5 percent and the Philippines at 4 percent. Europe, by contrast, produced 287,390 tonnes in 2019, just 0.8 percent of global output, and less than 1 percent of that came from microalgae. European microalgae are primarily produced on land, with photobioreactors accounting for 71 percent of production, ponds for 19 percent and fermenters for 10 percent. A survey of 447 manufacturing units across 23 countries found that over half produce microalgae or Spirulina, with Germany, Spain, France and Italy leading the sector. The most frequently cultivated species in Europe are Chlorella, Nannochloropsis and Haematococcus pluvialis, and the industry is uniquely positioned to supply high-value products such as nutraceuticals.

The food and health nexus is where microalgae have made their most visible commercial inroads. These organisms are among the healthiest sustainable functional food sources, rich in polyunsaturated fatty acids, vitamins, proteins, minerals, amino acids, pigments and phenolic compounds, with documented antibacterial, antioxidant, anti-inflammatory, antiviral, anti-obesity and anticancer activities. Spirulina, a prokaryotic cyanobacterium grown commercially for over 30 years, has been classified by the World Health Organisation as a health food, and both NASA and the European Space Agency recognise it as a candidate food for long-term space missions. Indigenous populations in Mexico and Africa have consumed it for centuries, crafting cakes known as tecuitlatl and dihe from lakeside harvests. Recent studies show that enriching pasta with 2 to 15 percent Spirulina powder increased protein, antioxidants, iron and calcium without harming texture, while biscuits fortified with 4 percent Spirulina saw protein content rise by 57 percent, and Spirulina-based white chocolate outscored conventional chocolate in sensory acceptance.

Chlorella vulgaris, another green microalga, contains 50 to 60 percent protein by dry weight, with an amino acid profile that meets or surpasses WHO and FAO nutritional standards. Approved species vary by country, reflecting a complex regulatory landscape: in the United States, the FDA grants GRAS status after rigorous testing, while in the European Union, foods not widely consumed before May 1997 are classified as novel foods requiring an EFSA safety assessment. One consumer hurdle is the intense green colour microalgae impart to foods, which the EFSA has addressed by approving two pale-coloured, low-chlorophyll Chlorella powders that are more visually neutral. Meanwhile, Dunaliella salina, a halophilic alga whose beta-carotene content can reach 14 percent of dry weight, supports the world’s largest commercial microalgae facilities, two Australian sites covering nearly 900 hectares. Haematococcus pluvialis supplies astaxanthin, a carotenoid valued at more than USD 240 million annually with a market price around USD 2,000 per kilogram, prized for neutralising singlet oxygen and scavenging free radicals.

Beyond human nutrition, microalgae are reshaping animal feeding and agriculture. Livestock farming demands extensive land and water while emitting considerable greenhouse gases, and algae can partially substitute traditional feed proteins while improving immune function, lipid metabolism, stress resistance and gut health. Over half of all Spirulina produced worldwide is used as a feed additive. In poultry, a 5 to 10 percent algae incorporation can partially replace conventional proteins, and chickens fed with Porphyridium showed egg yolk cholesterol reduced by 10 percent alongside darker, carotenoid-rich yolks. In ruminant studies, supplementing diets with Chlorella vulgaris or Nannochloropsis oculata reduced methane emissions while improving nutrient degradability. In aquaculture, microalgae feed larvae and juvenile fish, raise zooplankton, improve water quality through nutrient removal, and deliver natural omega-3 fatty acids and immunostimulants; shrimp fed with Phaeodactylum tricornutum and Tetraselmis showed significantly lower mortality after pathogen exposure. Microalgae also serve as biofertilisers and biostimulants, a market projected to reach USD 5,377.8 million by 2029 with a compound annual growth rate of 15.2 percent, as companies from Spain to India commercialise algal formulations that fix nitrogen and solubilise phosphorus.

The environmental services of microalgae may prove even more transformative. With global water demand expected to rise 20 to 30 percent by 2050, microalgae-based wastewater treatment offers low cost, low energy consumption, minimal sludge formation and nutrient recovery. One study using seven microalgae species in urban wastewater removed more than 80 percent of dissolved nitrogen and 87 percent of phosphorus. Recent innovations include membrane microalgal-bacterial coupling systems that remove antibiotic residues, a semi-transparent photovoltaic bioreactor that simultaneously treats wastewater, produces lipids and generates over 37 kWh per square metre of electricity, and a modular phototrophic biofilm reactor that cut phosphate by 92 percent and nitrate by 62 percent at an operating aquaculture facility. The French company ZENI is installing photobioreactors at factory wastewater outlets to strip nitrates and phosphates, while researchers at the University of Almería developed the ABACO-2 application to simulate algae-bacteria consortia for economical, odour-free treatment. On the carbon side, modelling studies suggest microalgae could reduce annual CO2 emissions by up to 2.35 gigatonnes, equivalent to 5.31 to 8.01 percent of the global reduction needed in 2020, and artificial intelligence tools such as GA-ANFIS models are being deployed to predict and optimise fixation rates.

Biofuels remain the most contentious frontier. The field spans four generations, from edible crop feedstocks to bioengineered organisms, with microalgae anchoring the third generation as a theoretically carbon-neutral fuel requiring little or no additional land. The US Department of Energy’s Aquatic Species Programme invested roughly USD 25 million between 1978 and 1995, and a subsequent report estimated the United States could produce 152 million tonnes of microalgae biomass annually using 268 million tonnes of CO2, with algal fuel potentially costing less than USD 4 per gallon gasoline equivalent when co-produced with algal protein. Yet the sector’s history is cautionary: Japan invested over USD 117 million in enclosed bioreactors that failed on inaccurate cost forecasts, and ExxonMobil eventually withdrew from its high-profile partnership. New momentum is building around sustainable aviation fuel, with Viridos securing USD 25 million from Breakthrough Energy Ventures, United Airlines Ventures and Chevron, Malaysia planning a 10,000-acre biorefinery in Sarawak targeting 100,000 barrels of crude algae oil per day by 2030, and Cepsa partnering with the Instituto Tecnológico de Canarias on a project aiming for 2.5 million tonnes of annual biofuel capacity with up to 90 percent lower CO2 emissions than conventional fuels.

Bioplastics complete the portfolio. Packaging accounts for roughly 40 percent of plastic use, and an estimated 24 to 34 million metric tonnes of plastic waste enter aquatic ecosystems each year. Microalgae synthesise starch, cellulose and polyhydroxyalkanoates that can be processed into biodegradable materials without competing with food crops. Researchers have produced antimicrobial films from Scenedesmus obliquus extracts blended with polyurethane and converted high-purity Chlorella starch into softer, more ductile thermoplastic starch than commercial potato-based equivalents. Startups and consortia from Indonesia to Sweden, including the EU-funded NENU2PHAR project and Umeå University’s Waste2Plastic initiative, are pushing toward industrial scale, though extensive life cycle assessment work is still needed. The review’s authors are candid about the obstacles: biomass production costs range from EUR 290 to EUR 587 per kilogram dry weight, microalgae-based carbon capture costs USD 800 to 1,600 per tonne, and a survey of 3,048 Spanish consumers found that roughly 85 percent lacked information about microalgae as food. Their prescription combines artificial intelligence and machine learning for cultivation optimisation, genetic engineering of high-value strains, biorefinery concepts that valorise every fraction of biomass, workforce training through initiatives such as the Algae Technology Educational Consortium, and coordinated policy support under the European Green Deal. If those pieces align, the authors conclude, these ancient photosynthetic cells could anchor a circular economy that feeds people, powers aircraft and cleans the planet’s water simultaneously.

Subject of Research: The role of microalgae biotechnology in advancing a sustainable blue bioeconomy

Article Title: Blue bioeconomy and biotechnology: towards a sustainably growing microalgae industry

Article References: Tang, D. Y. Y., Ooi, C., & Show, P. L. (2025). Blue bioeconomy and biotechnology: towards a sustainably growing microalgae industry. Blue Biotechnology, 2(1), Article 13. https://doi.org/10.1186/s44315-025-00036-8

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00036-8

Keywords: microalgae, blue bioeconomy, biotechnology, carbon capture, wastewater treatment, biofuels, nutraceuticals, animal feed, bioplastics, circular economy, photobioreactors, sustainability

The review frames biofuels as a carbon-neutral proposition in principle: the carbon dioxide released when a biofuel burns is offset by the carbon dioxide the feedstock absorbed while growing. That logic underpins projections from the International Energy Agency that biofuels will supply roughly 30 percent of the renewable energy sector by 2025, with production needing to rise dramatically, from about 9.7 million gigajoules per day to 46 million gigajoules per day by 2040. But not all biofuels are created equal. The authors organize the field into four generations, each defined by its feedstock and its trade-offs, and the trajectory from first to fourth generation tells a story of steadily decoupling fuel production from food production and land use.

First-generation biofuels, derived directly from food crops such as sugarcane, corn, wheat and vegetable oils, launched the renewable fuel movement but quickly ran into the food-versus-fuel dilemma. Diverting edible crops into fuel tanks raises food security concerns, drives land-use change and can trigger deforestation and soil degradation, eroding the very climate benefits these fuels were meant to deliver. Second-generation biofuels answered part of that critique by turning to non-edible lignocellulosic biomass: agricultural waste, forestry residues, switchgrass, poplar and reed canary grass. Because this material would otherwise go to waste, the net carbon balance approaches neutrality. The technical catch is recalcitrance. Lignin resists anaerobic fermentation and must be broken down with harsh pretreatments such as alkaline peroxide, concentrated acid or organic solvents before cellulases and beta-glucosidases can hydrolyze cellulose and hemicellulose into fermentable glucose. Microbes ranging from Penicillium capsulatum to thermophilic actinomycetes and the hyperthermophile Caldicellulosiruptor saccharolyticus can degrade hemicellulose, but processing costs and seasonal feedstock variability have kept second-generation fuels from scaling.

Third-generation biofuels shift the burden from land plants to microbes, and algae have emerged as the flagship feedstock. Research on microalgae for fuel dates to the 1950s, when Ostwald and Golueke in California tested algal species in anaerobic processes. Today the appeal is easy to quantify: many microalgae accumulate 50 to 70 percent of their dry weight as lipids under optimal conditions, and some species produce 10 to 20 times more biofuel per unit area than terrestrial crops, with certain strains doubling their biomass within 24 hours. Algae cultivation is also strikingly efficient at the level of carbon accounting, fixing about 1.83 grams of carbon dioxide for every gram of biomass generated. Mixotrophic cultivation, in which algae such as Chlorella protothecoides receive both light and an organic carbon source, has shown 69 percent higher lipid production and 61.5 percent lower carbon dioxide emissions than heterotrophic approaches. Crucially, algae can grow on non-arable land, in saline or brackish water, and even in wastewater, where they strip out nitrogen and phosphorus while producing fuel feedstock.

Fourth-generation biofuels push the concept further by marrying engineered organisms with carbon capture and storage. Synthetic biology and CRISPR-based editing are being used to build microbes that convert feedstocks into fuel while sequestering carbon, and thermochemical routes such as pyrolysis, gasification and solar-to-fuel conversion are being tuned to raise hydrocarbon yields. The cyanobacterium Synechocystis has become a workhorse model because its compact genome was among the first sequenced among photosynthetic organisms, making it an ideal platform for studying and engineering oxygenic photosynthesis. These systems remain experimental, but they point toward fuels that are not merely carbon-neutral but potentially carbon-negative.

The biotechnological toolkit driving all of this is expanding rapidly. Tissue culture, for instance, allows clonal propagation of biofuel crops under controlled conditions independent of climate, and callus cultures can be manipulated to accumulate lipids. In one striking example, in vitro-grown industrial hemp callus was hydrothermally liquefied into biocrude with a petroleum-like composition, yielding 22.61 percent biocrude by weight, composed of acids, ketones, aldehydes, aromatics and hydrocarbons. Genetic engineering of microbes has delivered equally concrete gains: an engineered Escherichia coli strain expressing genes including lacZ, gapA, ldhA and pflB showed an 85 percent improvement in bioethanol production from wheat straw. A consortium of Scheffersomyces stipitis and Zymomonas mobilis increased xylose consumption by 5.52 percent and ethanol titer by 6.52 percent, and further metabolic engineering of Z. mobilis lifted xylose consumption and ethanol titer by 15.36 percent and 6.81 percent respectively. Engineered Saccharomyces cerevisiae has even co-produced ethanol and the bioplastic precursor polyhydroxybutyrate from lignocellulosic biomass.

Metabolic engineering and enzyme optimization round out the arsenal. Researchers achieved 20 grams per liter of isobutanol from cheese whey using plasmid libraries and strain improvement in E. coli, and CRISPR-Cas9 editing enabled isobutanol production in Paenibacillus polymyxa. Consolidated bioprocessing, which folds enzyme production, polysaccharide hydrolysis and sugar fermentation into a single step, cuts costs by eliminating externally supplied enzymes; the thermophilic anaerobe Clostridium thermocellum is considered a leading biocatalyst for the approach because it both degrades cellulose and produces ethanol. Extraction is being modernized too, with ultrasound-assisted and supercritical fluid techniques reducing energy and solvent use, and pyrolysis offering an economically attractive thermal route from algae to bio-oil.

Turning algae into fuel at industrial scale still requires solving a chain of engineering problems. Cultivation can proceed in open ponds, which are cheap but vulnerable to contamination, or in closed photobioreactors, which deliver higher yields and purity at higher capital cost; vertical tubular reactors exchange gases more efficiently than horizontal ones but are prone to biofilm formation. Hybrid two-stage systems offer a compromise, growing biomass first in a photobioreactor and then shifting conditions to trigger lipid accumulation. Harvesting by flocculation and filtration can recover roughly 0.1 percent dry mass per liter, and solvent extraction, including cyclopentyl methyl ether, which achieved a 39.4 percent oil extraction rate in one study, feeds into transesterification for biodiesel or fermentation for ethanol. Light, temperature, carbon dioxide concentration, pH and nutrient availability all modulate yield, with elevated carbon dioxide around 10 percent shown to boost growth and lipid synthesis by 30 to 50 percent.

The economics improve further when algae are treated as a biorefinery feedstock rather than a single-purpose crop. Beyond fuel, microalgae yield proteins exceeding 30 percent of dry weight, omega-3 fatty acids, antioxidants, pigments such as astaxanthin and beta-carotene, and bioactive compounds including the immunosuppressive agent Microcolin-A from Lyngbya majuscula and the antiviral protein cyanovirin from Nostoc. Algal sterols show anticancer and anti-inflammatory properties, and species such as Chlorella and Arthrospira are already commercialized in health foods. Algal biomass also serves as a biofertilizer: cyanobacteria fix atmospheric nitrogen and suppress soil-borne pathogens, offering a renewable alternative to synthetic fertilizers. Japan’s commercial algal production in the 1960s, which generated roughly 5,000 metric tons of dry biomass and about 1.25 billion dollars in bio-products, foreshadowed this multiproduct model.

The review’s authors are candid that significant hurdles remain, including high production costs, water and nutrient demands, resource-intensive processing, and unresolved questions about the ecological risks of releasing genetically modified microorganisms. First-generation feedstocks still dominate the industry, a practice they call unsustainable given its conflict with food security. Their prescription is continued interdisciplinary work spanning biology, engineering and economics, paired with policies and public engagement that reward genuinely sustainable practices. If those pieces align, algae-derived fuels, boosted by CRISPR-engineered strains and integrated biorefineries, could move from promising laboratory systems to a mainstream pillar of a low-carbon energy future.

Subject of Research: Biotechnological advances, including genetic and metabolic engineering, for improving algal biofuel production and environmental sustainability

Article Title: Sustainable energy solutions: the role of biotechnology and algal biofuels in environmental preservation

Article References: Kumari, S., Dalania, K., Magotra, S., Singh, A. K., & Negi, N. P. (2025). Sustainable energy solutions: the role of biotechnology and algal biofuels in environmental preservation. Discover Biotechnology, 2(1), Article 16. https://doi.org/10.1007/s44340-025-00023-0

Image Credits: AI Generated

DOI: 10.1007/s44340-025-00023-0

Keywords: algal biofuels, biotechnology, CRISPR-Cas9, metabolic engineering, biodiesel, bioethanol, microalgae, biorefinery, carbon sequestration, lignocellulosic biomass, photobioreactors, sustainable energy

The commercial stakes are considerable. The global organic acids market is projected to reach 36.86 billion dollars by 2026, and in 2004 the United States Department of Energy identified twelve high-priority building-block chemicals obtainable from biomass, roughly seventy percent of which are organic acids. These include succinic acid, 3-hydroxypropionic acid, itaconic acid, and levulinic acid, compounds that serve as precursors for biodegradable plastics, solvents, pharmaceuticals, and food additives. Traditionally these chemicals come from petrochemical synthesis or heterotrophic fermentation, both of which carry substantial carbon footprints. Cyanobacteria offer a third route: photoautotrophic biosynthesis that consumes the greenhouse gas responsible for climate change as its raw material.

The metabolic logic behind this capability is elegant. Cyanobacteria fix atmospheric carbon dioxide through the Calvin-Benson-Bassham cycle, generating central intermediates such as pyruvate, phosphoenolpyruvate, and acetyl-CoA that feed into the tricarboxylic acid cycle. From these nodes, carbon can be channeled into acetate, lactate, citrate, succinate, fumarate, and malate. Intriguingly, cyanobacteria possess an atypical, incomplete TCA cycle lacking the canonical 2-oxoglutarate dehydrogenase complex. Instead, they bypass this step via 2-oxoglutarate decarboxylase and succinic semialdehyde dehydrogenase, an evolutionary adaptation that appears designed to preserve carbon skeletons for biosynthesis rather than burning them off as carbon dioxide. Some strains also harbor the glyoxylate shunt and a gamma-aminobutyric acid shunt, alternative routes that connect carbon metabolism with nitrogen assimilation and redox regulation.

The organisms also display a striking diurnal rhythm that researchers are learning to exploit. During daylight, cyanobacteria assimilate carbon dioxide into glycogen stores; when darkness falls and oxygen dwindles, they ferment these reserves, secreting organic acids and hydrogen. Under dark, anoxic conditions, Synechocystis sp. PCC 6803 has been shown to release more than 400 milligrams per liter of acetate, along with lactate, succinate, and malate, independent of nitrogen source. This natural overflow metabolism acts as a redox-balancing mechanism, dumping excess reducing equivalents when the cell’s usual sinks, such as glycogen and protein synthesis, are unavailable. Engineers are now working to redirect this flux deliberately toward single target products under continuous illumination.

Case studies demonstrate how far metabolic engineering can push these yields. In Synechocystis PCC 6803, inserting a codon-optimized phosphoketolase from Pseudomonas aeruginosa boosted acetate production fortyfold, and co-expressing phosphotransacetylase raised titers to 2.3 grams per liter, an eightyfold increase over the starting strain. Lactate engineering has been even more dramatic: combining overexpression of malic enzyme and d-lactate dehydrogenase with deletion of the acetate kinase gene produced a record 26.6 grams per liter of d-lactate from high-density cell cultures after seventy-two hours of fermentation. Because lactate is the monomer for polylactic acid, a biodegradable plastic used in packaging and 3D printing, such strains could eventually supply the bioplastics industry with carbon-negative feedstock.

Succinate, a top Department of Energy platform chemical used to make 1,4-butanediol, gamma-butyrolactone, and biodegradable polymers, has seen similar success. In Synechococcus elongatus PCC 7942, researchers used CRISPR interference to repress glycogen synthesis and succinate dehydrogenase while overexpressing key carboxylation and decarboxylation enzymes, achieving the highest cyanobacterial succinate titer reported to date: 4.8 grams per liter in twenty-eight days, rising to 8.9 grams per liter with reinoculation. A separate photomixotrophic strategy engineered the same strain to import glucose at low pH and export succinate at high pH, exploiting opposing proton symporters to reach 5.0 grams per liter in ten days. Even citrate, long considered too tightly regulated to accumulate, has been produced photoautotrophically in PCC 7002 using a theophylline-responsive riboswitch to throttle TCA flux, yielding more than a hundredfold increase over wild type.

Redox engineering has emerged as a central theme in these efforts. Cyanobacteria inherently produce abundant NADPH through photosynthesis, yet many fermentative enzymes prefer NADH, creating a cofactor mismatch that limits yields. Solutions include overexpressing transhydrogenases such as PntAB to interconvert the two pools, and site-directed mutagenesis to swap enzyme cofactor preferences, as demonstrated with an NADH-dependent lactate dehydrogenase from Lactobacillus bulgaricus that was redesigned to accept NADPH. Environmental tuning matters too: raising cultivation temperature from 30 to 37 degrees Celsius enhanced d-lactate and succinate production in PCC 6803, while mildly acidic conditions increase passive secretion of weak acids by boosting membrane permeability. Nitrogen starvation can push glycogen-deficient strains into a photo-catalytic state, continuously excreting alpha-ketoglutarate and pyruvate even without growth.

Formidable obstacles remain before these microbes can compete with petrochemical plants. Cyanobacteria grow slowly, allocate only a minor fraction of fixed carbon to target products, and suffer from genetic instability, low transformation efficiency, and byproduct formation as carbon leaks into competing pathways. Product recovery is another bottleneck: organic acids exist in ionized form at neutral pH, and traditional acidification with mineral acids generates mountains of inorganic salt waste. Photobioreactors struggle with uneven light penetration, limited gas transfer, and biofouling, and techno-economic and life-cycle assessments for engineered cyanobacterial systems remain scarce, making it difficult to judge commercial feasibility. Most studies to date remain at proof-of-concept or laboratory scale.

The road ahead is nonetheless rich with opportunity. Emerging tools include CRISPR-based gene repression and activation, riboswitches and light-inducible promoters that decouple growth from production, and adaptive laboratory evolution to breed acid-tolerant strains. Machine learning-guided flux modeling and multi-omics integration are converting strain design from trial-and-error into predictive optimization, while next-generation photobioreactors with optical waveguides and gas-permeable membranes promise better scalability. Co-cultures with heterotrophs, photomixotrophy using waste-derived carbon, and multi-product biorefineries coupling organic acids with biofuels and bioplastics could further improve economics. Greener recovery technologies, including membrane filtration, electrodialysis, and in situ product removal, are being developed to replace salt-generating acidification. If these threads converge, cyanobacteria could transform sunlight and carbon dioxide into the molecular backbone of a circular, fossil-free chemical economy, turning the planet’s oldest oxygen-makers into its newest industrial workhorses.

Subject of Research: Metabolic engineering of cyanobacteria for sustainable photosynthetic production of organic acids

Article Title: Advances in organic acid production using cyanobacteria: strategies and applications

Article References: Pathania, R., & Srivastava, A. (2025). Advances in organic acid production using cyanobacteria: strategies and applications. Blue Biotechnology, 2(1), Article 22. https://doi.org/10.1186/s44315-025-00045-7

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00045-7

Keywords: cyanobacteria, organic acids, metabolic engineering, synthetic biology, carbon dioxide fixation, succinate, lactate, TCA cycle, bioplastics, photobioreactors, CRISPRi, sustainable biomanufacturing