Screening of chemical modulators for lipid accumulation in Schizochytrium sp. S31

Harnessing oleaginous protist Schizochytrium for docosahexaenoic acid: Current technologies in sustainable production and food applications

Docosahexaenoic acid (DHA) exerts versatile roles in nutrition supplementation and numerous health disorders prevention. Global consumption demand for DHA has also been consistently increasing with enhanced health awareness. Oleaginous marine protist Schizochytrium is praised as a potential DHA source due to short growth cycle, convenient artificial culture, harmless to the human body, and easy manipulation of the DHA synthesis pathway. However, factors including strain performances, fermentation parameters, product harvest and extraction strategies, safety and stability maintenance, and also application limitations in health and functional properties affect the widespread adoption of Schizochytrium DHA products. This review provides a comprehensive summary of the current biotechnologies used for tackling factors affecting the Schizochytrium DHA production, with special focuses on Schizochytrium strain improvement technologies, fermentation optimization projects, DHA oil extraction strategies, safety evaluations and stability maintenance schemes, and DHA product application approaches in foods. Inspired by systematic literature investigations and recent advances, suggestive observations composed of improving strain with multiple breeding technologies, considering artificial intelligence and machine learning to optimize the fermentative process, introducing nanoparticles packing technology to improve oxidation stability of DHA products, covering up DHA odor defect with characteristic flavor foods, and employing synthetic biology to construct the structured lipids with DHA to exploit potential functions are formed. This review will give a guideline for exploring more Schizochytrium DHA and propelling the application development in food and health.

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.

Enhanced fatty acid storage combined with the multi-factor optimization of fermentation for high-level production of docosahexaenoic acid in Schizochytrium sp

Schizochytrium sp. hasreceived much attention for itsability to synthesize and accumulate high-level docosahexaenoic acid (DHA), which can reach nearly 40 % of total fatty acids. In this study, the titer of DHA in Schizochytrium sp. was successfully improved by enhancing DHA storage through overexpressing the diacylglycerol acyltransferase (ScDGAT2C) gene, as well as optimizing the supply of precursors and cofactors required for DHA synthesis by response surface methodology. Notably, malic acid, citric acid, and biotin showed synergistic and time-dependent effects on DHA accumulation. The maximum lipid and DHA titers of the engineered Schizochytrium sp. strain reached 84.28 ± 1.02 g/L and 42.23 ± 0.69 g/L, respectively, with the optimal concentration combination (1.62 g/L malic acid + 0.37 g/L citric acid + 8.28 mg/L biotin) were added 48 h after inoculation. This study provides an effective strategy for improving lipid and DHA production in Schizochytrium sp.

Simultaneous production of high-value lipids in Schizochytrium sp. by synergism of chemical modulators

The study focuses on the simultaneous improvement of biomass, lipid, and docosahexaenoic acid (DHA) productivities in a single reactor using modulator control strategies. The efficacy of three different biochemical modulators, sesamol (Ses), 6-benzylaminopurine (6-BAP), and ethylenediaminetetraacetic acid (EDTA), as potential stimulants in augmenting the biomass, lipid, and DHA production of Schizochytrium sp. MTCC 5890 was elucidated. After 48 h of cultivation, among tested modulators, the individual supplementation of 6-BAP and Ses showed improvement in biomass, lipid, and DHA accumulation by 28.2%, 56.1%, and 87.2% and 21.7%, 47.9%, and 91%, respectively, over the non-supplemented group. In addition, the cooperative effect of selected concentrations, i.e., 10 mgL-1 6-BAP and 200 mgL-1 Ses, further increased the productivities of biomass of 13.5 gL-1d-1 ± 0.66, lipid of 7.4 gL-1d-1 ± 0.69, and DHA of 3.2 gL-1d-1 ± 1.09 representing 8%, 39%, and 69% increase over the individual addition of 6-BAP or Ses, respectively, in batch culture. Supplementation with 6-BAP + Ses at 12 h of time point eventually increased the lipid yield to 15.6 ± 0.42 gL-1 from 7.88 ± 0.31 gL-1 (control) and DHA yield to 6.4 ± 0.11 gL-1 from 2.23 ± 0.09 gL-1 (control), respectively. Furthermore, the process was optimized in continuous culture supplemented with 6-BAP + Ses for enhanced productivities. Continuous culture resulted in maximum biomass (2.04 ± 1.12 gL-1 day-1), lipid (1.0 ± 0.73 gL-1 day-1), and DHA (0.386 ± 0.22 gL-1 day-1) productivities, which were higher as compared with the batch and fed-batch processes by 26 ± 1.21%, 22 ± 1.01%, and 21 ± 0.98% and 24 ± 0.45%, 16 ± 0.38%, and 14 ± 0.12%, respectively. This work represents the potential application of the combined effect of modulators for the simultaneous enhancement of biomass production and lipid and DHA productivities. KEY POINTS: • The cumulative study of 6-BAP and sesamol proved to be more efficient in the simultaneous production of biomass, lipid, and DHA in a single reactor. • Addition of a combination of 6-BAP + Ses remarkably increased the biomass, lipid, and DHA productivities in tandem in continuous culture.

Efficient Biosynthesis of Odd-Chain Fatty Acids via Regulating the Supply and Consumption of Propionyl-CoA in Schizochytrium sp

Odd chain fatty acids (OCFAs) are high-value-added compounds with great application in the field of food and medicine. As an oleaginous microorganism, Schizochytrium sp. has the potential to produce OCFAs efficiently. Propionyl-CoA is used as a precursor to synthesize OCFAs through the fatty acid synthetase (FAS) pathway, so its flow direction determines the yield of OCFAs. Here, different substrates were assessed to promote propionyl-CoA supply for OCFA accumulation. Moreover, the methylmalonyl-CoA mutase (MCM) was identified as the key gene responsible for propionyl-CoA consumption, which promotes the propionyl-CoA to enter into the tricarboxylic acid cycle rather than the FAS pathway. As one of the classic B₁₂-dependent enzymes, the activity of MCM can be inhibited in the absence of B₁₂. As expected, the OCFA accumulation was greatly increased. However, the removal of B₁₂ caused growth limitation. Furthermore, the MCM was knocked out to block the consumption of propionyl-CoA and to maintain cell growth; results showed that the engineered strain achieved the OCFAs titer of 2.82 g/L, which is 5.76-fold that of wild type. Last, a fed-batch co-feeding strategy was developed, resulting in the highest reported OCFAs titer of 6.82 g/L. This study provides guidance for the microbial production of OCFAs.

Metabolic analysis of Schizochytrium sp. mutants with high EPA content achieved with ARTP mutagenesis screening

Eicosapentaenoic acid (EPA) belonged to the ω-3 series of polyunsaturated fatty acids and had physiological functions lipid as regulating blood lipid and preventing cardiovascular diseases. Schizochytrium sp. was considered to be a potential industrial fermentation strain of EPA because of its fast growth, high oil content, and simple fatty acid composition. However, Schizochytrium sp. produced EPA with low production efficiency and a long synthesis path. This research aims to improve the yield of EPA in Schizochytrium sp. by ARTP mutagenesis and to reveal the mechanism of high-yield EPA through transcriptome analysis. ARTP mutagenesis screening yielded the mutant M12 that whereas the productivity of EPA increased 108% reaching 0.48 g/L, the total fatty acid concentration was 13.82 g/L with an increase of 13.7%. The transcriptomics revealed 2995 differentially expressed genes were identified between M12 and the wild-type strain and transcripts involved in carbohydrate, amino acid, energy, and lipid metabolism were up-regulated. Among them, the hexokinase (HK) and the phosphofructokinase genes (PFK), which can catalyze pyruvate to acetyl-CoA, were increased 2.23-fold and 1.78-fold. Glucose-6-phosphate dehydrogenase (G6PD) and glutamate dehydrogenase (GLDH), which can both generate NADPH, were increased by 1.67-fold and 3.11-fold. Furthermore, in the EPA synthesis module, the expression of 3-oxoacyl-[acyl-carrier protein] reductase(fabG) and carbonyl reductase 4 / 3-oxoacyl-[acyl-carrier protein] reductase beta subunit(CBR4), also up-regulated 1.11-fold and 2.67-fold. These may lead to increases in cell growth. The results provide an important reference for further research on promoting fatty acid and EPA accumulation in Schizochytrium sp.

Propanol and 1, 3-propanediol enhance fatty acid accumulation synergistically in Schizochytrium ATCC 20888

The effects of propanol and 1, 3-propanediol on fatty acid and biomass accumulation in Schizochytrium ATCC 20888 were explored. Propanol increased the contents of saturated fatty acids and total fatty acids by 55.4 and15.3%, while 1, 3-propanediol elevated the polyunsaturated fatty acids, total fatty acids and biomass contents by 30.7, 17.0, and 6.89%. Although both of them quench ROS to increase fatty acids biosynthesis, the mechanisms are different. The effect of propanol did not reflect on metabolic level while 1, 3-propanediol elevated osmoregulators contents and activated triacylglycerol biosynthetic pathway. The triacylglycerol content and the ratio of polyunsaturated fatty acids to saturated fatty acids were significantly increased by 2.53-fold, which explained the higher PUFA accumulation in Schizochytrium after adding 1, 3- propanediol. At last, the combination of propanol and 1, 3-propanediol further elevated total fatty acids by approximately 1.2-fold without compromising cell growth. These findings are valuable for scale-up production of designed Schizochytrium oil for various application purposes.

Integration of the Exogenous Tuning of Thraustochytrid Fermentation and Sulfur Polymerization of Single-Cell Oil for Developing Plant-like Oils

In this study, we have demonstrated a bioprocessing approach encompassing the exogenous addition of low-molecular-weight compounds to tune the fatty acid (FA) profile in a novel thraustochytrid strain to produce desirable FAs. Maximum lipid recovery (38%, dry wt. biomass) was obtained at 1% Tween 80 and 0.25 mg/L of Vitamin B12. The transesterified lipid showed palmitic acid (C16, 35.7% TFA), stearic acid (C18, 2.1% TFA), and oleic acid (C18:1, 18.7% TFA) as the main components of total FAs, which are mainly present in plant oils. Strikingly, D-limonene addition in the fermentation medium repressed the production of polyunsaturated fatty acid (PUFAs). Sulfur-polymerization-guided lipid separation revealed the presence of saturated (SFAs, 53% TFA) and monounsaturated fatty acids (MUFAs, 46.6% TFA) in thraustochytrid oil that mimics plant-oil-like FA profiles. This work is industrially valuable and advocates the use of sulfur polymerization for preparation of plant-like oils through tuneable thraustochytrid lipids.

Microalgal Biomass as Feedstock for Bacterial Production of PHA: Advances and Future Prospects

The search for biodegradable plastics has become the focus in combating the global plastic pollution crisis. Polyhydroxyalkanoates (PHAs) are renewable substitutes to petroleum-based plastics with the ability to completely mineralize in soil, compost, and marine environments. The preferred choice of PHA synthesis is from bacteria or archaea. However, microbial production of PHAs faces a major drawback due to high production costs attributed to the high price of organic substrates as compared to synthetic plastics. As such, microalgal biomass presents a low-cost solution as feedstock for PHA synthesis. Photoautotrophic microalgae are ubiquitous in our ecosystem and thrive from utilizing easily accessible light, carbon dioxide and inorganic nutrients. Biomass production from microalgae offers advantages that include high yields, effective carbon dioxide capture, efficient treatment of effluents and the usage of infertile land. Nevertheless, the success of large-scale PHA synthesis using microalgal biomass faces constraints that encompass the entire flow of the microalgal biomass production, i.e., from molecular aspects of the microalgae to cultivation conditions to harvesting and drying microalgal biomass along with the conversion of the biomass into PHA. This review discusses approaches such as optimization of growth conditions, improvement of the microalgal biomass manufacturing technologies as well as the genetic engineering of both microalgae and PHA-producing bacteria with the purpose of refining PHA production from microalgal biomass.

Enhancement of lipid accumulation and docosahexaenoic acid synthesis in Schizochytrium sp. H016 by exogenous supplementation of sesamol

Schizochytrium sp. is one of the most promising marine oleaginous microorganisms for industrial production of docosahexaenoic acid (DHA). In this study, the exogenous supplementation of 1 mM sesamol to the fermentation medium effectively prevented the peroxidation of polyunsaturated fatty acids in the fermentation process, which thereby significantly increasing the lipid and DHA yield by 53.52% and 78.30%, respectively. The addition of sesamol also increased the total antioxidant capacity of cells and induce the gene expression of polyketide synthase and antioxidant enzyme system. Moreover, the supply of nicotinamide adenine dinucleotide phosphate was regulated by sesamol by inhibiting the malic enzyme activity and promoting the glucose-6-phosphate dehydrogenase activity. Finally, fed-batch fermentation showed that the addition of sesamol significantly enhanced the DHA yield by 90.76%. This study provides an important reference for enhancing the DHA productivity of Schizochytrium sp. in industrial fermentation.

Production of polyunsaturated fatty acids by Schizochytrium (Aurantiochytrium) spp

Diverse health benefits are associated with dietary consumption of omega-3 long-chain polyunsaturated fatty acids (ω-3 LC-PUFA), particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Traditionally, these fatty acids have been obtained from fish oil, but limited supply, variably quality, and an inability to sustainably increase production for a rapidly growing market, are driving the quest for alternative sources. DHA derived from certain marine protists (heterotrophic thraustochytrids) already has an established history of commercial production for high-value dietary use, but is too expensive for use in aquaculture feeds, a much larger potential market for ω-3 LC-PUFA. Sustainable expansion of aquaculture is prevented by its current dependence on wild-caught fish oil as the source of ω-3 LC-PUFA nutrients required in the diet of aquacultured animals. Although several thraustochytrids have been shown to produce DHA and EPA, there is a particular interest in Schizochytrium spp. (now Aurantiochytrium spp.), as some of the better producers. The need for larger scale production has resulted in development of many strategies for improving productivity and production economics of ω-3 PUFA in Schizochytrium spp. Developments in fermentation technology and metabolic engineering for enhancing LC-PUFA production in Schizochytrium spp. are reviewed.

The strategies to reduce cost and improve productivity in DHA production by Aurantiochytrium sp.: from biochemical to genetic respects

The marine oleaginous protist Aurantiochytrium sp. (Schizochytrium sp.) is a well-known docosahexaenoic acid (DHA) producer and its different DHA products are the ideal substitute for the traditional fish oil resource. However, the cost of the DHA products derived from Aurantiochytrium sp. (Schizochytrium sp.) is still high, limiting their wide applications. In order to reduce the cost or improve the productivity of DHA from the microbial resource, many researches are focusing on exploring the renewable and low-cost materials as feedbacks, and/or the stimulators for biomass and DHA production. In addition, the genetic engineering is also being used in the Aurantiochytrium sp. (Schizochytrium sp.) system for further improvement. These break the bottleneck of the DHA production by Aurantiochytrium sp. (Schizochytrium sp.) in some degree. In this review, the strategies used currently to reduce cost and improve DHA productivity, mainly from the utilizations of low-cost materials and effective stimulators to the genetic engineering perspectives, are summarized, and the availabilities from the cost perspective are also evaluated. This review provides an overview about the strategies to revolve the production cost and yield of the DHA by Aurantiochytrium sp. (Schizochytrium sp.), a theoretical basis for genetic modification of Aurantiochytrium sp. (Schizochytrium sp.), and a practical basis for the development of DHA industry. KEY POINTS : • Utilizations of various low-cost materials for DHA production • Inducing the growth and DHA biosynthesis by the effective stimulators • Reducing cost and improving DHA productivity by genetic modification • The availability from cost perspective is evaluated.

Different Classes of Phytohormones Act Synergistically to Enhance the Growth, Lipid and DHA Biosynthetic Capacity of Aurantiochytrium sp. SW1

In the present study, the impact of eight phytohormones from six different classes on the growth, lipid and docosahexaenoic acid (DHA) biosynthetic capacity of Aurantiochytrium sp. SW1 (SW1) was evaluated. Kinetin (KIN), jasmonic acid (JA) and gibberellic acid (GA) significantly enhanced the growth and DHA production of SW1 by 16%-28% and 66%-84% in comparison to the control, respectively. The synergistic effect of these three phytohormones, evaluated by the response surface methodology (RSM), showed that a combination of 3.6 mg/L GA, 2.0 mg/L KIN and 20.0 mg/L JA further increased the growth and DHA production of SW1 by 16% to 28% and 22% to 36%, respectively, in comparison to the individual supplementation. The synergistic effect of these phytohormones was also shown to be time-dependent, where feeding at 24 h of cultivation led to 15%, 26% and 35% further increments in the biomass, lipid and DHA production in comparison to that of 0 h, respectively. The determination of stress markers, antioxidant enzymes and key enzymes involved in fatty acid biosynthesis aided to elucidate the potential mechanism underlying the improvement of growth and DHA production by SW1 at various times of feeding. Supplementation with the phytohormones at 24 h exhibited the maximum impact on reducing the level of reactive oxygen species (ROS) and malondialdehyde (MDA), as well as augmented the antioxidants (superoxide dismutase and catalase) and key metabolic enzymes involved in lipogenesis (malic, glucose-6-phosphate dehydrogenase and ATP-citrate lyase) in comparison to the control and other time points. This study signifies the potential application of phytohormones for improving the growth, lipid and DHA production in Aurantiochytrium spp.

Lab-Scale Optimization of Aurantiochytrium sp. Culture Medium for Improved Growth and DHA Production

Thraustochytrids have gained increasing relevance over the last decades, due to their fast growth and outstanding capacity to accumulate polyunsaturated fatty acids (PUFAs), particularly docosahexaenoic acid (DHA). In this context, the present work aimed to optimize the growth performance and DHA yields by improving the culture medium of Aurantiochytrium sp. AF0043. Accordingly, two distinct culture media were optimized: (i) an inorganic optimized medium (IOM), containing only monosodium glutamate and glucose as nitrogen and carbon sources, respectively; and (ii) an organic and sustainable waste-based optimized medium (WOM), containing corn steep powder and glycerol, added in fed-batch mode, as nitrogen and carbon sources, respectively. Overall, the lab-scale optimization allowed to increase the biomass yield 1.5-fold and enhance DHA content 1.7-fold using IOM. Moreover, WOM enabled a 2-fold increase in biomass yield and a significant improvement in lipid contents, from 22.78% to 31.14%. However, DHA content was enhanced almost 3-fold, from an initial content of 10.12% to 29.66% of total fatty acids contained in the biomass. Therefore, these results strongly suggest, not only that the production pipeline was significantly improved but also confirmed the potential use of Aurantiochytrium sp. AF0043 as a source of DHA.

Nutrient recovery from tofu whey wastewater for the economical production of docosahexaenoic acid by Schizochytrium sp. S31

Docosahexaenoic acid plays a vital role in human health as it is essential for the proper function of the nervous system and for visual functions. To decrease the cost of docosahexaenoic acid production by Schizochytrium, the cost of the medium should be further decreased. In this study, the use of tofu whey wastewater to culture Schizochytrium sp. for docosahexaenoic acid production was tested, with the goal of reducing the medium cost. The results indicated that tofu whey wastewater presented a better culture performance with respect to biomass, lipid, and docosahexaenoic acid production compared with three traditional media. Through simple pH adjustment, the biomass and docosahexaenoic acid productivity reached 1.89 and 0.24 g/L/day, respectively, which were much higher than those obtained using traditional medium. The removal efficiency of chemical oxygen demand, total nitrogen, and total phosphorus reached 64.7, 66.0, and 59.3%, respectively. Due to the rich nutrients in tofu whey wastewater, the use of extra nitrogen source was avoided and the total medium cost for docosahexaenoic acid production in cultures using tofu whey wastewater was <1/3 of that of traditional media. This result indicated that tofu whey wastewater is an effective and economic basal medium for docosahexaenoic acid production by Schizochytrium sp.

Metabolic engineering to enhance biosynthesis of both docosahexaenoic acid and odd-chain fatty acids in Schizochytrium sp. S31

BACKGROUND

Docosahexaenoic acid (DHA, C22:6) and odd-chain fatty acids (OCFAs, C15:0 and C17:0) have attracted great interest, since they have been widely used in food and therapeutic industries, as well as chemical industry, such as biodiesel production and improvement. The oil-producing heterotrophic microalgae Schizochytrium sp. 31 is one of main DHA-producing strains. Recently, it was found that Schizochytrium can also synthesize OCFAs; however, contents and titers of DHA and OCFAs in Schizochytrium are still low, which limit its practical application.

RESULTS

In this study, we found that acetyl-CoA carboxylase suffered from a feedback inhibition by C16-CoA in Schizochytrium, and relief of the inhibition resulted in improved both lipid content and the ratio of OCFAs in total fatty acids. Based on this finding, a novel strategy for elevating both DHA and OCFAs contents was established. First, the total lipid accumulation was increased by overexpressing a malic enzyme from Crypthecodinium cohnii to elevate NADPH supply. Second, the inhibition effect on acetyl-CoA carboxylase was relieved by overexpressing a codon-optimized ELO3 gene from Mortierella alpina, which encodes an elongase enzyme responsible for converting C16 into C18 fatty acids. After the above two-step engineering, contents of DHA and OCFAs were increased by 1.39- and 3.30-fold, reaching a level of 26.70 and 25.08% of dry cell weight, respectively, which are the highest contents reported so far for Schizochytrium. The titers of DHA and OCFAs were elevated by 1.08- and 2.57-fold, reaching a level of 3.54 and 3.32 g/L, respectively. Notably, the OCFAs titer achieved was 2.66-fold higher than the highest reported in Escherichia coli (1.25 g/L), implying potential value for industry application. To reveal the potential metabolic mechanism for the enhanced biosynthesis of both DHA and OCFAs, LC-MS metabolomic analysis was employed and the results showed that the pentose phosphate pathway and the glycolysis pathway were strengthened and intracellular propionyl-CoA concentration were also significantly increased in the engineered Schizochytrium, suggesting an increased supply of NADPH, acetyl-CoA, and propionyl-CoA for DHA and OCFAs accumulation.

CONCLUSIONS

The discovery provides a new source of OCFAs production, and proposes a new strategy to improve contents and titers of both DHA and OCFAs in Schizochytrium. These will be valuable for improving commercial potential of Schizochytrium and guiding the engineering strategy in other fatty acids producing heterotrophic microalga.

Screening chemical modulators of benzoic acid derivatives to improve lipid accumulation in Schizochytrium limacinum SR21 with metabolomics analysis

BACKGROUND

Schizochytrium sp. is a marine fungus with great potential as an alternative commercial source of lipids rich in polyunsaturated fatty acids (PUFAs). To further increase lipid accumulation in Schizochytrium sp., the effect of exogenous additives has become one of the hotspots of current research. Although benzoic acid derivatives showed positive effects on lipid accumulation in Schizochytrium, the biochemical mechanism needs further investigation.

RESULTS

Four benzoic acid derivatives (sodium benzoate, p-aminobenzoic acid, p-methyl benzoic acid and folic acid) were screened and evaluated for their effect on lipid accumulation in Schizochytrium limacinum SR21. The lipid yield was increased by 56.84% with p-aminobenzoic acid (p-ABA) at a concentration of 200 mg/L among the four tested chemical modulators. The metabolomics analysis showed that 200 mg/L p-ABA was optimal for promoting glucose catabolism in glycolysis with an increase in the mevalonate pathway and a weakening of the tricarboxylic acid (TCA) cycle. Moreover, p-ABA increased NADPH generation by enhancing the pentose phosphate pathway (PPP), ultimately redirecting the metabolic flux to lipid synthesis. Fed-batch fermentation further proved that p-ABA could significantly increase the yield of lipid by 30.01%, reaching 99.67 g/L, and the lipid content was increased by 35.03%, reaching 71.12%. More importantly, the yields of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were increased by 33.28% and 42.0%, respectively.

CONCLUSION

The addition of p-ABA could promote the synthesis of tetrahydrofolate, enhancing NADPH, which ultimately promoted the flow of carbon flux to lipid synthesis. These findings provide a valuable strategy for improving the lipid accumulation in Schizochytrium by additives.

Quercetin potentiates the concurrent hyper-accumulation of cellular biomass and lipids in Chlorella vulgaris

Provision of chemical modulators has emerged as an effective strategy to govern cell growth and development. Here, the impact of flavonoid quercetin on algal growth, lipid accumulation and transcriptional patterns was investigated in the green microalga Chlorella vulgaris. These results demonstrated that quercetin (15 μg/l) significantly enhanced the cellular biomass and photosynthetic efficiency, with up to 2.5-fold in the biomass in the stationary phase. Lipidomic analyses revealed that lipid content was increased by 1.8-fold. Furthermore, the functional mechanism of quercetin on the molecular level was dissected by transcriptomic analysis. Results revealed that quercetin upregulated the expression pattern of key genes involved in cellular signaling mechanisms such as phosphatidylinositol 4-kinase α, thus consequently enhanced cell growth. Altogether, the data present in this study demonstrate the dramatic role of quercetin on enhancing microalgal biomass and lipid accumulation by unprecedented regulation, of key metabolic nodes, for the first time and provide a novel insight into microalgal metabolism and regulation.