Distribution of long-chain polyunsaturated fatty acids and the effects of molasses on DHA production in Thraustochytrium sp. 26185

Abstract

Thraustochytrium sp. 26185 is a microorganism that produces docosahexaenoic acid (DHA) and other long-chain polyunsaturated fatty acids (LCPUFA). However, expression patterns of the key genes involved in LCPUFA synthesis during cell growth remain unclear. Therefore, this study investigated the distribution of LCPUFAs in glycerol backbones that form phospholipids and triacylglycerols (TAG) during cell growth. Integrated transcriptomic and lipidomic analyses were performed at different growth time points. LCPUFAs were associated with glycerol backbones after 12 h of phospholipid biosynthesis and synthesized TAGs at 72 h. In addition, the effects of different carbon sources (glucose, sugarcane molasses, and mixtures of each with glycerol) on growth and LCPUFA production were evaluated. The highest biomass (7.02 ± 0.05 g/L), cell growth rate (1.03 ± 0.12 g/L/d), lipid content (4.72 ± 0.02 g/L), and DHA production (1.55 ± 0.02 g/L) obtained at 72 h when sugarcane molasses was added as the carbon source. Gene expression analysis revealed upregulated expression of the fatty acid and phospholipid biosynthetic genes encoding acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), and lysophosphatidylcholine acyltransferase 2 (LPCAT2) at 6–12 h. In contrast, the expression of diacylglycerol acyltransferase (DGAT) for TAG biosynthesis was upregulated after 12 h in the sugarcane molasses medium. These findings revealed the sequential distribution of DHA with growth, and indicated glucose could be substituted with sugarcane molasses for DHA production in Thraustochytrium sp. 26185.