Docosahexaenoic acid production by Schizochytrium sp.: review and prospect

Docosahexaenoic acid-enriched diet improves the flesh quality of freshwater fish (Megalobrama amblycephala): Evaluation based on nutritional value, texture and flavor

Docosahexaenoic acid (DHA) is a potential regulatory substance for flesh quality of fish, while the related evaluation is still barely. In this study, the effects of DHA-enriched diets on the flesh quality of freshwater fish (Megalobrama amblycephala) were investigated systematically. The sub-adult M. amblycephala were randomly fed with control diet (CON), 0.2% DHA diet (DL) or 0.8% DHA diet (DH). After 12-week feeding trial, the DH group flesh had higher concentrations of essential amino acids and polyunsaturated fatty acids compared to the CON group. Meanwhile, the hardness, springiness, shear force and moisture-holding capacity, as well as the values of umami, richness and sweetness were also improved by DH. The non-targeted metabolomics analysis revealed the key metabolites that may have significantly positive influence on flavor. Collectively, the diet supplementation with 0.8% DHA could achieve the improvement of the flesh quality in terms of nutritional value, texture and flavor in freshwater fish.

Formation mechanism of off-flavor and the inhibition regulatory strategies in the algal oil-loaded emulsions-a review

Algal oil rich in docosahexaenoic acid is easily oxidized and degraded to produce volatile short-chain compounds, leading to the deterioration of product flavor. Currently, the emulsion delivery of algal oil provides a promising approach to minimize oxidative deterioration and conceal its off-flavor. However, algal oil emulsions would also experience unanticipated oxidation as a result of the large specific surface area between the aqueous phase and the oil phase. The current paper offers a mechanism overview behind off-flavor formation in algal oil emulsions and explores corresponding strategies for the inhibition regulation. Additionally, the paper delves into the factors influencing lipid oxidation and the perception of off-flavors in such emulsions. To mitigate the development of off-flavors in algal oil emulsions resulting from oxidation, it is crucial to decline the likelihood of lipid oxidation and proactively prevent the creation of off-flavors whenever possible. Minimizing the release of volatile off-flavor compounds that are inevitably generated is also considered effective for weakening off-flavor. Moreover, co-encapsulation with particular desirable aroma substances could improve the overall flavor characteristics of emulsions.

Docosahexaenoic Acid (DHA) and Eicosapentaenoic Acid (EPA)-Should They Be Mandatory Supplements in Pregnancy?

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are essential fatty acids for the human body. Seafood and microalgae are the most important sources of omega-3 fatty acids. Supplementation with 200 mg/day of DHA during pregnancy and breastfeeding has been suggested for women and infants in countries with low seafood consumption. Maternal concentration of DHA and EPA was associated with concentration in cord blood and breast milk. High concentrations of DHA and EPA were identified at the level of retinal photoreceptors and neuronal cell membranes. It was observed that supplementation with DHA and EPA during pregnancy had beneficial effects on the neurological development of the fetus and infant by improving language, memory, attention, and hand coordination, affecting sleep patterns, and improving visual acuity. Beneficial effects on the development of the infant were also associated with the maternal intake of omega-3 fatty acids during breastfeeding. Supplementation with DHA and EPA may reduce the risk of preterm birth but also of preeclampsia in low-risk pregnancies. Women of childbearing age should have an intake of 250 mg/day of DHA + EPA from their diet or supplements. To reduce the risk of premature birth, pregnant women must additionally receive at least 100-200 mg of DHA every day. It is recommended that supplementation with omega-3 fatty acids starts before 20 weeks of pregnancy. Beneficial effects on the mother have been identified, such as the reduction of postpartum depression symptoms, the decrease of cardiovascular risk, and the anti-inflammatory role.

Turning waste into treasure: A new direction for low-cost production of lipid chemicals from Thraustochytrids

Thraustochytrids are marine microorganisms known for their fast growth and ability to store lipids, making them useful for producing polyunsaturated fatty acids (PUFAs), biodiesel, squalene, and carotenoids. However, the high cost of production, mainly due to expensive fermentation components, limits their wider use. A significant challenge in this context is the need to balance production costs with the value of the end products. This review focuses on integrating the efficient utilization of waste with Thraustochytrids fermentation, including the economic substitution of carbon sources, nitrogen sources, and fermentation water. This approach aligns with the 3Rs principles (reduction, recycling, and reuse). Furthermore, it emphasizes the role of Thraustochytrids in converting waste into lipid chemicals and promoting sustainable circular production models. The aim of this review is to emphasize the value of Thraustochytrids in converting waste into treasure, providing precise cost reduction strategies for future commercial production.

Enhancing docosahexaenoic acid production from Schizochytrium sp. by using waste Pichia pastoris as nitrogen source based on two-stage feeding control

To reduce the cost of docosahexaenoic acid (DHA) production from Schizochytrium sp., the waste Pichia pastoris was successfully used as an alternative nitrogen source to achieve high-density cultivation during the cell growth phase. However, due to the high oxygen consumption feature when implementing high-density cultivation, the control of both the nitrogen source and dissolved oxygen concentration (DO) at each sufficient level was impossible; thus, two realistic control strategies, including "DO sufficiency-nitrogen limitation" and "DO limitation-nitrogen sufficiency", were proposed. When using the strategy of "DO sufficiency-nitrogen limitation", the lowest maintenance coefficient of glucose (12.3 mg/g/h vs. 17.0 mg/g/h) and the highest activities of related enzymes in DHA biosynthetic routes were simultaneously obtained; thus, a maximum DHA concentration of 12.8 ± 1.2 g/L was achieved, which was 1.58-fold greater than that of the control group. Overall, two-stage feeding control for alternative nitrogen sources is an efficient strategy to industrial DHA fermentation.

Engineering Fatty Acid Biosynthesis in Microalgae: Recent Progress and Perspectives

Microalgal lipids hold significant potential for the production of biodiesel and dietary supplements. To enhance their cost-effectiveness and commercial competitiveness, it is imperative to improve microalgal lipid productivity. Metabolic engineering that targets the key enzymes of the fatty acid synthesis pathway, along with transcription factor engineering, are effective strategies for improving lipid productivity in microalgae. This review provides a summary of the advancements made in the past 5 years in engineering the fatty acid biosynthetic pathway in eukaryotic microalgae. Furthermore, this review offers insights into transcriptional regulatory mechanisms and transcription factor engineering aimed at enhancing lipid production in eukaryotic microalgae. Finally, the review discusses the challenges and future perspectives associated with utilizing microalgae for the efficient production of lipids.

Biomass productivity and characterization of Tetradesmus obliquus grown in a hybrid photobioreactor

In this study, the effects of CO2 addition on the growth performance and biochemical composition of the green microalga Tetradesmus obliquus cultured in a hybrid algal production system (HAPS) were investigated. The HAPS combines the characteristics of tubular photobioreactors (towards a better carbon dioxide dissolution coefficient) with thin-layer cascade system (with a higher surface-to-volume ratio). Experimental batches were conducted with and without CO2 addition, and evaluated in terms of productivity and biomass characteristics (elemental composition, protein and lipid contents, pigments and fatty acids profiles). CO2 enrichment positively influenced productivity, and proteins, lipids, pigments and unsaturated fatty acids contents in biomass. The HAPS herein presented contributes to the optimization of microalgae cultures in open systems, since it allows, with a simple adaptation-a transit of the cultivation through a tubular portion where injection and dissolution of CO2 is efficient-to obtain in TLC systems, greater productivity and better-quality biomass.

Lipidomic and transcriptomic analysis of the increase in eicosapentaenoic acid under cobalamin deficiency of Schizochytrium sp

Schizochytrium sp. is a heterotrophic microorganism capable of accumulating polyunsaturated fatty acids and has achieved industrial production of docosahexaenoic acid (DHA). It also has the potential for eicosapentaenoic acid (EPA) production. In this study, it was found that the cell growth, lipid synthesis and fatty acid composition of Schizochytrium sp. were significantly affected by the level of cobalamin in the medium, especially with regard to the content of EPA in the fatty acids. The content of EPA in the fatty acids increased 17.91 times, reaching 12.00%, but cell growth and lipid synthesis were significantly inhibited under cobalamin deficiency. The response mechanism for this phenomenon was revealed through combined lipidomic and transcriptomic analysis. Although cell growth was inhibited under cobalamin deficiency, the genes encoding key enzymes in central carbon metabolism were still up-regulated to provide precursors (Acetyl-CoA) and reducing power (NADPH) for the synthesis and accumulation of fatty acids. Moreover, the main lipid subclasses observed during cobalamin deficiency were glycerolipids (including glycerophospholipids), with EPA primarily distributed in them. The genes involved in the biosynthesis of these lipid subclasses were significantly up-regulated, such as the key enzymes in the Kennedy pathway for the synthesis of triglycerides. Thus, this study provided insights into the specific response of Schizochytrium sp. to cobalamin deficiency and identified a subset of new genes that can be engineered for modification.

Fine-tuning of key parameters to enhance biomass and nutritional polyunsaturated fatty acids production from Thraustochytrium sp

The escalating demand for long-chain polyunsaturated fatty acids (PUFAs) due to their vital health effects has deepened the exploration of sustainable sources. Thraustochytrium sp. stands out as a promising platform for omega-3 and 6 PUFA production. This research strategically optimizes key parameters: temperature, salinity, pH, and G:Y:P ratio and the optimized conditions for maximum biomass, total lipid, and DHA enhancement were 28 °C, 50 %, 6, and 10:1:2 respectively. Process optimization enhanced 32.30 and 31.92 % biomass (9.88 g/L) and lipid (6.57 g/L) yield. Notably, DHA concentration experienced a substantial rise of 69.91 % (1.63 g/L), accompanied by notable increases in EPA and DPA by 82.69 % and 31.47 %, respectively. MANOVA analysis underscored the statistical significance of the optimization process (p < 0.01), with all environmental factors significantly influencing biomass and lipid data (p < 0.05), particularly impacting DHA production. Thraustochytrium sp. can be a potential source of commercial DHA production with the fine-tuning of these key process parameters.

Marine Microalgae Schizochytrium sp. S31: Potential Source for New Antimicrobial and Antibiofilm Agent

BACKGROUND

The rise of antibiotic-resistant bacteria necessitates the discovery of new, safe, and bioactive antimicrobial compounds. The antibacterial and antibiofilm activity of microalgae makes them a potential candidate for developing natural antibiotics to limit microbial infection in various fields.

OBJECTIVE

This study aimed to analyze the antibacterial effect of the methanolic extract of Schizochytrium sp. S31 microalgae by broth microdilution and spot plate assays.

METHODS

The antibacterial effects of Schizochytrium sp. S31 extract was studied on gramnegative pathogens, Pseudomonas aeruginosa, Escherichia coli 35218, Klebsiella pneumonia, which cause many different human infections, and the gram-positive pathogen Streptococcus mutans. At the same time, the antibiofilm activity of the Schizochytrium sp. S31 extract on Pseudomonas aeruginosa and Escherichia coli 35218 bacteria were investigated by crystal violet staining method.

RESULTS

Schizochytrium sp. S31 extract at a 60% concentration for 8 hours displayed the highest antibacterial activity against P. aeruginosa, E. coli 35218, and K. pneumonia, with a decrease of 87%, 92%, and 98% in cell viability, respectively. The experiment with Streptococcus mutans revealed a remarkable antibacterial effect at a 60% extract concentration for 24 hours, leading to a notable 93% reduction in cell viability. Furthermore, the extract exhibited a dose-dependent inhibition of biofilm formation in P. aeruginosa and E. coli 35218. The concentration of 60% extract was identified as the most effective dosage in terms of inhibition.

CONCLUSION

This research emphasizes the potential of Schizochytrium sp. S31 as a natural antibacterial and antibiofilm agent with promising applications in the pharmaceutical sectors. This is the first study to examine the antibacterial activity of Schizochytrium sp. S31 microalgae using broth microdilution, spot plate assays, and the antibiofilm activity by a crystal staining method. The findings of this study show that Schizochytrium sp. S31 has antibacterial and antibiofilm activities against critical bacterial pathogens.

Development of a novel microplate for high-throughput screening and optimization of DHA producing strains based on CFD technology

Microtiter plates are suitable for screening and process development of most microorganisms. They are currently the container of choice for high-throughput and small-scale microbial culture, but require optimization for specific work. In this research, a novel type of microtiter plate was developed using computational fluid dynamics (CFD) technology. The new plate provided high oxygen supply and optimal mixing effects for the fermentation culture of docosahexaenoic acid (DHA) producing strains, surpassing the conventional method of strain screening with shake flasks, which was insufficient. The shape of the microtiter plate was modified, and baffles were introduced to improve mass transfer and oxygen supply effects in the vibrating bioreactor. CFD technology was used to model the new plate's characteristics, establishing the superiority of hexagonal microtiter plates with six baffles. Parameters in the incubation process, such as vibration frequency and liquid load, were optimized, and the final result achieved an oxygen transfer coefficient (KL a) of 0.61 s-1 and a volume power input of 2364 w m-3 , which was four to five times better than the original 96-well plate. The culture results optimized by the model were also verified. Therefore, this new microtiter plate provides a powerful tool for future high-throughput screening of strains.

Deciphering and engineering the polyunsaturated fatty acid synthase pathway from eukaryotic microorganisms

Polyunsaturated fatty acids (PUFAs) are important nutrients that play important roles in human health. In eukaryotes, PUFAs can be de novo synthesized through two independent biosynthetic pathways: the desaturase/elongase pathway and the PUFA synthase pathway. Among them, PUFAs synthesized through the PUFA synthase pathway typically have few byproducts and require fewer reduction equivalents. In the past 2 decades, numerous studies have been carried out to identify, analyze and engineer PUFA synthases from eukaryotes. These studies showed both similarities and differences between the eukaryotic PUFA synthase pathways and those well studied in prokaryotes. For example, eukaryotic PUFA synthases contain the same domain types as those in prokaryotic PUFA synthases, but the number and arrangement of several domains are different; the basic functions of same-type domains are similar, but the properties and catalytic activities of these domains are somewhat different. To further utilize the PUFA synthase pathway in microbial cell factories and improve the productivity of PUFAs, many challenges still need to be addressed, such as incompletely elucidated PUFA synthesis mechanisms and the difficult genetic manipulation of eukaryotic hosts. In this review, we provide an updated introduction to the eukaryotic PUFA synthase pathway, summarize the functions of domains and propose the possible mechanisms of the PUFA synthesis process, and then provide future research directions to further elucidate and engineer the eukaryotic PUFA synthase pathway for the maximal benefits of humans.

Dietary Schizochytrium Microalgae Affect the Fatty Acid Profile of Goat Milk: Quantification of Docosahexaenoic Acid (DHA) and Its Distribution at Sn-2 Position

The objective of this study was to detect the influence of dietary Schizochytrium microalgae on milk composition, milk fatty acids, and milk sn-2 fatty acids in goat's milk. Firstly, we could see that the fat content increased in low microalgae supplementation goat's milk (LM, 15 g/day) and the lactose content decreased in medium microalgae supplementation goat's milk (MM, 25 g/day) compared with control goat's milk (C, 0 g/day). Moreover, the absolute concentration of the docosahexaenoic acid (DHA) of LM, MM, and high microalgae supplementation (HM, 35 g/day) goat's milk was 29.485, 32.351, and 24.817 mg/100 g raw milk, respectively, which were all higher than that in the control goat's milk with 4.668 mg/100 g raw milk. In addition, the sn-2 DHA content increased in MM and HM goat's milk. However, the decreasing trend of the sn-2 DHA content was observed in LM goat's milk. As for other fatty acids, the oleic acid (C18:1n9c) and linolenic acid (C18:3n3) content decreased and increased, respectively, in all experimental goat milk. Finally, an interesting phenomenon was found, which was that docosanoic acid (C22:0) and tetracosenic acid (C24:1) were only detected in test goat's milk. Consequently, the phenomena of this study demonstrated that dietary Schizochytrium microalgae have an obvious effect on the fatty acid and sn-2 fatty acid profile of goat's milk, and they provide an effective method to improve the content of goat's milk DHA in practical production.