Metabolic engineering of Schizochytrium sp. for superior docosahexaenoic acid production

Schizochytrium sp. is an industrial producer of docosahexaenoic acid (DHA), which is an important omega-3 polyunsaturated fatty acid used in the nutraceutical and food industry. Here, we rewired the carbon metabolism of Schizochytrium sp. ATCC20888 for superior DHA production and constructed 18 engineered strains through combinatorial gene manipulation of 8 crucial genes (acc, acl, ampD, dga1, mae, mfe1, pex10, and zwf) related to lipogenesis. Reducing 8-oxidations (Delta pex10, Delta mfe1), reinforcing the biosynthetic precursors supply (OACC, OACL, OAMPD), reinforcing NADPH supply (OMAE, OZWF), or promoting TAG formation (ODGA1) efficiently promoted DHA and lipid production of Schizochytrium. MAE and DGA1 overexpression exhibited cooperativity towards increasing DHA production and lipogenesis in the WT strain and ACC-overexpression strain, but had no cooperative advantage in the Delta pex10 strain. The highest lipid content (82.2%) and DHA yield (7.04 g/L) were obtained in an engineered strain OACL-ACC/Delta pex10, which is 72.1% higher than DHA yield of parental strain. Therefore, inhibition of 8-oxidations and ample biosynthetic precursors supply are the determining factors for high DHA productivity and lipid accumulation of Schizochytrium.