Delineating metabolomic changes in native isolate Aurantiochytrium for production of docosahexaenoic acid in presence of varying carbon substrates

Abstract

Oils rich in polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) have industrial significance due to their benefits in human nutrition and health. In this context, our preliminary screening with glucose (i.e., 2%, 3%, 4%, 6%, 8% and 10% w/v), in a marine indigenous thraustochytrid Aurantiochytrium sp., revealed that a concentration of 3% (w/v) was the optimal for further study. Henceforth, the impact of complementation to improve the biomass and DHA production were assessed with other alternative carbon substrates like galactose, fructose, xylose, sucrose, and glycerol. Our results demonstrate that the overall biomass and DHA productivities were maximal in 3% (w/v) glycerol, i.e. 1.91 g L−1 D−1, and 134.76 mg L−1 D−1, respectively. Also, utilization profiles of different carbon substrates demonstrate that although glycerol (0.174 g h−1) has a lower consumption rate than glucose (0.209 g h−1), galactose and fructose (0.208 g h−1), it results in higher biomass (Yx/s) yield of 0.5 g g−1 of the substrate. Further the investigation was done by qualitative metabolomics through gas chromatography-mass spectrometry (GC-MS) identified 34 metabolites comprised of fatty acids, sugars, and organic acids which were found to be significantly regulated. This led to our hypothesis that glycerol can induce cell growth with improved fatty acid yields via., upregulation of pentose phosphate pathway. In conclusion, this study demonstrates efficient valorization of biorefinery by-products (such as crude glycerol) as a cost-effective alternative for the production of high-value added PUFAs from heterotrophic thraustochytrids, the essential ingredients for food, nutraceutical and pharmaceutical industries.