Abstract
BackgroundSchizochytrium 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.ResultsFour 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.ConclusionThe 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.
Highlights
Schizochytrium sp. is a marine fungus with great potential as an alternative commercial source of lipids rich in polyunsaturated fatty acids (PUFAs)
Effects of different benzoic acid derivatives on lipid yield To screen the benzoic acid derivatives, Schizochytrium limacinum SR21 was cultured in fermentation medium supplemented with different concentration of the solution stocks
The results showed that p-aminobenzoic acid (p-ABA) was the best benzoic acid derivative, and the optimal concentration was 0.2 g/L for the lipid yield
Summary
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. Benzoic acid derivatives showed positive effects on lipid accumulation in Schizochytrium, the biochemical mechanism needs further investigation. To further increase lipid accumulation and DHA yield in Schizochytrium sp., several strategies of fermentation process optimization have been performed. The regulation of lipids and polyunsaturated fatty acids by exogenous addition has become one of the hotspots of current research. Yu et al reported that 6-benzylaminopurine led to a 25.9% increase in lipid yield in Schizochytrium sp., reaching 52.8% of biomass [9]. Zhang et al noted that the addition of p-methyl benzoic acid was able to increase the growth of oleaginous yeast, resulting in a higher lipid accumulation [16]. Sofia et al reported that benzoic acid had a dramatic effect on intracellular phospholipid content, but the stress response mechanism was unclear [17]
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