Search Results (106)

Palmitoleic acid (POA; 16:1 n-7 or cis-9 16:1) is a bioactive monounsaturated fatty acid (FA) with emerging metabolic and skin-health relevance, yet conventional botanical and animal sources provide limited and variable levels. Here we report on the development of a high-yield POA product platform in the heterotrophic microalga Prototheca moriformis through targeted genetic engineering. A Δ9-fatty acid desaturase from Macadamia integrifolia (MiSAD1618) was integrated using a phosphite-based selection system. Primary screening identified stable transformants producing up to 54% POA of total fatty acids, compared to 0.8% in the parental strain. In 1 L shake-flask cultivation, POA reached up to 58.2% of total fatty acids. In a 1 L fed-batch fermentation, the engineered strain accumulated 47.8 g/L of lipids with 43.5% POA after 96 h of fermentation, corresponding to 20.8 g/L of POA. GC–MS analysis of 4,4-dimethyloxazoline (DMOX) derivatives confirmed that the major 16:1 isomer was 16:1 n-7 (Δ9). Together, these results establish P. moriformis as a scalable fermentation platform for producing POA-rich oil and highlight its potential as an efficient alternative source of POA, providing a foundation for further strain and process optimization toward commercial production. Full article

The use of microalgae as a food source is limited by consumers’ dislike of their organoleptic traits, primarily the intense green color and bitter taste associated with high chlorophyll content. The eukaryotic microalgae Chlorella vulgaris can grow under heterotrophic conditions, providing the opportunity to cultivate chlorophyll-less strains. In this work we applied random mutagenesis for breeding chlorophyll-deficient C. vulgaris strains. Wild-type strain was UVC-radiated, and 12 colonies with changed pigmentation were selected. Based on phenotypic stability two mutants, M6 and M11, were selected for characterization of growth, pigment and biomass accumulation. Cultivation under photo-, mixo- and heterotrophic conditions revealed distinct phenotypes for the two mutants. M6 remained chlorophyll-deficient in all cultivation conditions tested, while chlorophyll was observed in M11 when grown under light. Under heterotrophic and mixotrophic growth conditions, both mutants were chlorophyll-deficient while biomass productivity, protein content, and amino acid composition remained similar to wild type. Characterization of the cellular ultrastructure of the wild type and mutants using cryo Focused Ion-Beam Scanning Electron Microscopy revealed that functional chloroplasts and thylakoid membranes were absent in the mutants. Our work demonstrates how a simple approach using UV mutagenesis and visual screening can provide novel strains of C. vulgaris with traits for improved consumer acceptance, without compromising the use of the algae biomass as a protein-rich food source. Full article

Aquaculture sustainability requires a reduction in the reliance on marine-derived raw materials such as fish oil in aquafeeds while maintaining fish health and product quality. This study investigated the effects of replacing fish oil with plant oils supplemented with DHA-rich Schizochytrium limacinum biomass on the gut microbiota of European sea bass (Dicentrarchus labrax). S. limacinum SR21—an oleaginous microalga naturally rich in omega-3 fatty acids—was produced through heterotrophic fermentation using crude glycerol, a waste stream from biodiesel production, within a circular economy framework. A 21-week feeding trial was conducted in an indoor recirculating aquaculture system using 280 fish distributed across eight tanks. Four experimental diets were tested: fish oil-based (FO), plant oil-based without microalga (VO + 0), and plant oil-based supplemented with 5% (VO + 5) or 10% (VO + 10) microalgal biomass. Gut microbiota was analyzed in 22 fish per group using 16S rRNA gene sequencing. While alpha and beta diversity analyses of gut microbiota revealed modest structural shifts at phylum and class ranks, genus-rank differences were evident, with Lactobacillus and Clostridium sensu stricto associated with FO and VO + 0 diets, and Pseudomonas and Staphylococcus enriched in microalga-supplemented groups. Functional inference highlighted enhanced bile acid biosynthesis and carbohydrate metabolism in VO + 0, whereas antioxidant-related pathways, including ubiquinone and carotenoid biosynthesis, were stimulated in VO + 5 and VO + 10 groups. These results demonstrate that S. limacinum biomass modulates microbiota functional capacity, potentially contributing to oxidative stress mitigation and host resilience. The findings support microbiota-informed feed formulation strategies to advance sustainable aquaculture. Full article

Increasing demands for improved energy efficiency and resource recovery in wastewater management have driven intensified research on microalgal–bacterial consortia (M-BC). This technological approach represents one of the most promising and continuously evolving concepts for integrated wastewater treatment and energy recovery. M-BC systems exploit complementary processes, including photosynthesis, oxygen production, nutrient uptake by microalgae, as well as heterotrophic degradation of organic contaminants and CO₂ generation by bacteria. Laboratory- and pilot-scale studies demonstrate that such integration can substantially reduce energy demand while significantly improving technological performance. Metabolic synergy, metabolite exchange, intercellular communication, and the specific aggregate architecture collectively determine the stability and high productivity of these consortia. Depending on operational conditions, M-BC may occur as suspended cultures, biofilm-based systems, or granules, which differ in process characteristics and biomass recovery potential. Available evidence indicates that M-BC biomass can serve as a highly efficient substrate for anaerobic digestion (AD). The methane production potential of M-BC reaches 350–365 mL CH₄/gVS, and following pretreatment may increase to 530–560 mL CH₄/gVS, exceeding typical ranges reported for conventional sewage sludge. These values were obtained under specific process conditions and depend on biomass characteristics, consortium structure, inoculum type, and operational parameters; therefore, their generalisation should be interpreted with caution. However, practical implementation remains constrained by process-related barriers directly affecting AD performance, including extracellular polymeric substance (EPS)-mediated hydrolysis limitation and nitrogen-associated inhibition linked to low C/N ratios and ammonia accumulation. Additional challenges include seasonal variability in biomass composition and incomplete understanding of M-BC behaviour under anaerobic conditions, particularly at scale. This paper provides a comprehensive and integrative analysis of the structure and biochemistry of M-BC biomass, their ecological mechanisms, technological configurations, and current knowledge regarding their susceptibility to anaerobic digestion. The review identifies the key biological, chemical, and process-related barriers and highlights research directions required for future integration of M-BC into circular wastewater treatment systems and energy-oriented biomass valorisation. Full article

Heterotrophic bacteria and microalgae are key regulators of marine biogeochemical cycles. The phycosphere, a nutrient-rich microenvironment surrounding microalgae, serves as a crucial interface for bacterial–algal interactions. Our previous work identified Opacimonas immobilis LMIT016^T, a phycosphere isolate from the diatom Actinocyclus curvatulus that possesses the smallest genome within the Alteromonadaceae family. However, its adaptation mechanisms to the phycosphere remain unclear, particularly given its extensive genome streamlining, a process involving the selective loss of non-essential and energetically costly genes to enhance fitness in nutrient-specific niches. Here, the co-cultivation experiments demonstrated significant mutual growth promotion between LMIT016^T and its host microalgae, with the bacterium forming dense attachments on diatom surfaces. Genomic analysis revealed that in addition to loss of motility-related genes, the strain exhibits a substantial reduction in c-di-GMP signaling components, including both synthases and receptors. Conversely, LMIT016^T harbors numerous genes essential for extracellular polysaccharide (EPS) biosynthesis and adhesion, supporting long-term attachment and biofilm formation. Other retained genes encode pathways for nutrient acquisition, stress response, and phosphate and nitrogen metabolism, reflecting its adaptations to the nutrient-rich phycosphere. Furthermore, the genome of LMIT016^T encodes two polysaccharide utilization loci (PULs) targeting laminarin and α-1,4-glucans, whose functions were experimentally validated by the transcriptional induction of the corresponding carbohydrate-active enzyme genes. These findings indicate that this strain counterbalances genome reduction by enhancing its attachment capabilities and metabolic specialization on algal polysaccharides, potentially facilitating stable association with diatom cells. Our results suggest that genome streamlining may represent an alternative ecological strategy in the phycosphere, highlighting a potential evolutionary trade-off between metabolic efficiency and niche specialization. Full article

Astaxanthin, a high-value keto-carotenoid with potent antioxidant and health-promoting properties, has gained global attention as a sustainable nutraceutical and biotechnological product. The green microalgae Haematococcus pluvialis and Chromochloris zofingiensis represent two promising natural producers, yet they differ markedly in physiology, productivity, and industrial scalability. This review provides a focused comparative analysis of these two species, emphasizing their quantitative performance differences. H. pluvialis can accumulate astaxanthin up to ~3–5% of dry biomass but typically reaches biomass densities of only 5–10 g L⁻¹, whereas C. zofingiensis achieves ultrahigh biomass concentrations of 100–220 g L⁻¹ under heterotrophic fed-batch fermentation, although its astaxanthin content is much lower (~0.1–0.5% DW). While H. pluvialis remains the benchmark for natural astaxanthin due to its exceptionally high cellular content, its thick cell wall, slow growth, and strict phototrophic requirements impose major cost and operational barriers. In contrast, C. zofingiensis exhibits rapid and flexible growth under heterotrophic, mixotrophic, or phototrophic conditions and can achieve ultrahigh biomass in fermentation, though its ketocarotenoid flux and astaxanthin accumulation remain comparatively limited. Meanwhile, a rapidly growing patent landscape demonstrates global technological competition, with major portfolios emerging in China, the United States, and Europe, spanning chemical synthesis, microbial fermentation, algal metabolic engineering, and high-density cultivation methods. These patents reveal clear innovation trends—ranging from solvent-free green synthesis routes to engineered microalgae and yeast chassis for enhanced astaxanthin production—which increasingly shape industrial development strategies. By synthesizing recent advances in metabolic engineering, two-stage cultivation, and green extraction technologies, this review identifies key knowledge gaps and outlines a practical roadmap for developing next-generation astaxanthin biorefineries, with an emphasis on scalable production and future integration into broader biorefinery frameworks. The findings aim to guide future research and provide actionable insights for scaling sustainable, cost-effective production of natural astaxanthin. Full article

Treating wastewater with a low carbon-to-nitrogen (C/N) ratio remains a major challenge for conventional biological processes because insufficient organic carbon limits heterotrophic denitrification. To address this issue, microalgae-based photobioreactors offer a sustainable alternative that couples nutrient removal with biomass valorization. This study systematically evaluated the effects of four key operational parameters—initial inoculum density, aeration rate, light intensity, and photoperiod—on nutrient removal, biomass productivity, and metabolite accumulation of Auxenochlorella pyrenoidosa (A. pyrenoidosa) treating synthetic low C/N wastewater. Optimal operating conditions were identified as an initial OD₆₈₀ of 0.1, aeration rate of 2 L air min⁻¹, light intensity of 112 μmol m⁻² s⁻¹, and a 16L:8D photoperiod. Under these conditions, the photobioreactor achieved 86.35% total nitrogen and 98.43% total phosphorus removal within 11 days while producing biomass rich in proteins, polysaccharides, and lipids. Metagenomic analysis revealed a metabolic transition from denitrification-driven pathways during early operation to assimilation-dominated nitrogen metabolism under optimized conditions, emphasizing the synergistic interactions within algal–bacterial consortia. These findings demonstrate that optimized A. pyrenoidosa-based photobioreactors can effectively recover nutrients and produce valuable biomass, offering a viable and sustainable solution for the treatment of low C/N wastewater. Full article

The accelerating pace of global population growth, urbanization, and industrialization is exerting considerable pressure on freshwater resources. In developing countries, where infrastructure constraints often hinder the adoption of advanced treatment technologies, cost-effective and efficient wastewater solutions are essential. Algal–bacterial bioremediation represents a promising, eco-friendly method for removing organic pollutants through biological processes. This study evaluates a hybrid treatment system composed of three ponds: a covered anaerobic pond for organic matter digestion, a microalgal pond equipped with rotating biological contactors (RBCs) that facilitate interactions between heterotrophic bacteria and diatoms, and a final settling pond. Granular activated carbon embedded within the RBC enhances biofilm formation by attracting heterotrophic bacteria, thereby increasing treatment efficiency. Under optimal conditions—10 g of activated carbon and 1.7 d hydraulic retention time—the system achieved removal efficiencies of 95.8% for total suspended solids (TSS), 96.3% for turbidity, 85% for biological oxygen demand (BOD), and 99.9% for Escherichia coli. Bacteriological analysis showed complete removal of fecal coliform and total coliform. The characteristics of the outflow treated wastewater are 3 mg/L, 0.9 NTU, and 3.2 mg/L for TSS, turbidity, and BOD, respectively, while E. coli detection is under detection limit. The treated effluent complies with Category A for the reuse of treated wastewater in the Egyptian code for the reuse of treated municipal wastewater for agricultural purposes, offering a scalable and sustainable solution for wastewater management in resource-constrained regions. Full article

Objectives: The aim of this experiment was to explore how the addition of Schizochytrium powder to the feeding ration affected the production performance, egg quality, and antioxidant function of chickens. Schizochytrium powder is a unicellular spherical marine microalga that can be cultivated through heterotrophic fermentation, with characteristics including rapid cell growth, stable composition, and ease of large-scale production. Experimental design: Three hundred and twenty 33-week-old chickens with similar egg production rates and body weights were selected and randomly divided into four groups, with five replicates each and 16 hens in each replicate. The control group (Group I) was fed a corn–soybean meal basal diet, while the test groups were supplemented with 0.5% (Group II), 1.0% (Group III), and 2.0% (Group IV) Schizochytrium powder on top of this basal diet, respectively. The pretest period was 1 week, and the main test period was 8 weeks. The results revealed the following: (1) Compared with Group I, the average daily feed intake (ADFI) and laying rate (LR) were significantly lower (p < 0.05) in Group IV, and there was no significant difference (p > 0.05) in the ADFI and LR between Groups II and III. (2) Compared with Group I, the eggshell strength (ES) and docosahexaenoic acid (DHA) content of Groups II, III, and IV were significantly higher (p < 0.05). (3) Compared with Group I, serum triglyceride (TG) content was significantly decreased (p < 0.05), and serum low-density lipoprotein (LDL) content was significantly increased (p < 0.05) in Groups II, III, and IV. Serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and peroxidase (PO) activities were significantly higher (p < 0.05) and serum malondialdehyde (MDA) content was significantly lower (p < 0.05) in Groups II, III, and IV compared to Group I. In conclusion, adding Schizochytrium powder to the feeding ration could affect chickens’ production performance, increase egg DHA content, and improve the antioxidant capacity of the organism. Based on the results of this study, we recommend a ratio of 1.0% Schizochytrium powder addition. 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

The use of lactose-utilizing microalgae offers a sustainable and cost-effective approach for the bioconversion of dairy industry side-streams and the reduction in microalgae production costs. This work aims to improve the biomass productivity of the lactose-utilizing microalgal strain Graesiella emersonii MSCL 1718 in concentrated cheese whey permeate. It was demonstrated that the mixotrophic growth of the axenic G. emersonii culture resulted in a significantly higher biomass productivity in 20% permeate medium compared to the heterotrophic cultivation. Furthermore, supplementation of the permeate medium with iron, zinc, cobalt, and molybdenum resulted in 12.8%, 12.9%, 9.3%, and 28.9% significant increases (p < 0.05) in biomass synthesis, respectively, compared to the control permeate group. In the subsequent experiment, G. emersonii cultivated in molybdenum-supplemented permeate resulted in 0.34 ± 0.02 g/(L·d) biomass productivity and twofold higher lipid content (30.21 ± 1.29%) compared to the photoautotrophic control in defined synthetic medium. Analysis of the fatty acid composition revealed a twofold increase in saturated fatty acids, reaching 62.16% under mixotrophic cultivation in permeate, compared with the photoautotrophic control. Overall, concentrated cheese permeate proved to be a suitable medium for G. emersonii biomass production, supporting both enhanced growth and increased lipid accumulation. Full article

Winery wastewater (WWW), if released untreated, poses a serious environmental threat due to its high organic load. In this study, Chlorella vulgaris was cultivated in diluted WWW to assess its suitability as a culture medium. Two outdoor cultivation systems—a 270 L raceway and a 40 L bubble column—were operated over 33 days using synthetic medium (control) and WWW. A flow cytometry (FC) protocol was implemented to monitor key physiological parameters in near-real time, including cell concentration, membrane integrity, chlorophyll content, cell size, and internal complexity. At the end of cultivation, the bubble column yielded the highest cell concentrations: 2.85 × 10⁶ cells/mL (control) and 2.30 × 10⁶ cells/mL (WWW), though with lower proportions of intact cells (25% and 31%, respectively). Raceway cultures showed lower cell concentrations: 1.64 × 10⁶ (control) and 1.54 × 10⁶ cells/mL (WWW), but higher membrane integrity (76% and 36% for control and WWW cultures, respectively). On average, cells grown in the bubble column had a 22% larger radius than those in the raceway, favouring sedimentation. Heterotrophic cells were more abundant in WWW cultures, due to the presence of organic carbon, indicating its potential for use as animal feed. This study demonstrates that FC is a powerful, real-time tool for monitoring microalgae physiology and optimising cultivation in complex effluents like WWW. Full article

In recent years, microalgae have gained significant biotechnological importance as a sustainable source of various metabolites of industrial interest. Among these, paramylon, a polysaccharide produced by the microalga Euglena gracilis, stands out for its diverse applications in biomedicine and pharmaceuticals. E. gracilis is an adaptable secondary eukaryote capable of growing photoautotrophically, heterotrophically and mixotrophically. During photoautotrophic growth, varying light conditions impact biomass and paramylon production. To investigate the effects of varying illumination more thoroughly, we designed and built a modular photobioreactor that allowed us to simultaneously evaluate the photoautotrophic growth of E. gracilis under twelve different light conditions: seven single-spectrum lights (ultraviolet, royal blue, blue, green, red, far-red, and infrared) and five composite-spectrum lights (3000 K, 10,000 K, and 30,000 K white lights, amber light, and “Full-spectrum” light). The 24-day growing kinetics were recorded, and the growth parameters were calculated for each light regime. Both growth curves and pigment composition present differences attributable to the light regime used for cell culture. Additionally, photosynthetic and respiratory machinery functionality were proven by oximetry. Finally, our results strongly suggest that the far-red component enhances paramylon production during the stationary phase. Full article

Powdered oil ingredients are widely used across food, nutrition, and personal care industries, but they are typically produced through encapsulation technologies that involve multiple additives and stabilizers. These systems can compromise oxidative stability, clean-label compliance, and functional performance. Here, we present the development and characterization of a novel high-oleic algal powder (HOAP) produced from a heterotrophically fermented microalgae. The production strain was developed through classical mutagenesis to enhance oleic acid and lipid accumulation. Three independent fermentation batches at a 20 L scale demonstrated strong reproducibility in key metrics, including dried-cell weight (210.0 g per L on average, CV% = 0.7), oil content (62.0% of DCW on average, CV% = 2.0), and oleic acid (88.8% of total fatty acids on average, CV% = 0.1). HOAP exhibited a favorable nutritional profile (e.g., high monounsaturated fat and fiber, low sugar and moisture) and good oxidative stability under ambient and accelerated storage conditions. Microbiological analyses confirmed compliance with food-grade standards, and in silico allergenicity screening revealed no clinically relevant homologs. Unlike traditional oil powders, HOAP does not require encapsulation and retains oil within a natural protein–fiber matrix, offering both functional and clean-labeling advantages. Its compositional attributes and stability profile support potential use in food, nutrition, and the delivery of bioactive nutrients. These findings establish HOAP as a next generation of oil powder ingredients with broad application potential. Full article

Global population growth makes an increase in food production inevitable, and protein plays a vital role as an essential nutrient. However, as the proportion of land used for agriculture and animal protein production decreases, the search for sustainable, low-cost alternatives to proteins has become a research priority. Microalgae can synthesize a wide range of proteins, among which phycocyanin is of interest due to its unique biological activity. It has a complete amino acid profile, contains essential amino acids, and is a high-quality source of protein. Most of the existing studies have focused on single influencing factors, improved methods, or specific culture conditions for the synthesis of phycocyanin in microalgae and have not yet analyzed the culture conditions, influencing factors, and improved strategies for the synthesis of phycocyanin in microalgae in a systematic and integrated manner, and the studies lacked comprehensiveness and consistency. In this paper, the key factors, mechanisms of action, and improvement strategies affecting the accumulation of phycocyanin in microalgae are reviewed. The growth of microalgae under autotrophic, heterotrophic, and mixed culture conditions and their effects on phycocyanin synthesis were systematically described. The aim is to accelerate the application of phycocyanin in the food industry and alternative proteins by improving the production efficiency of microalgae, promoting their comprehensive utilization, and injecting a new impetus into the development of a sustainable protein industry. Full article