Yacon (Smallanthus sonchifolius) tuber: A novel and promising feedstock for enhanced high-value docosahexaenoic acid production by Schizochytrium sp.

Abstract

Fermentation cost and oxygen-mediated lipid peroxidation have become economic and technical bottlenecks for the commercialization of docosahexaenoic acid (DHA) from microorganisms. Yacon (Smallanthus sonchifolius) tuber is rich in fructan, phenolics and other nutrients, and it represents a low-cost and abundant feedstock for microbial fermentation. Herein, yacon tuber hydrolysate (YTH) yielded by exo-inulinase was used as a novel potential substrate for Schizochytrium sp. ATCC 20888 to produce DHA. Under the optimized medium composition of reducing sugar of 100 g/L, C/N ratio of 30 and C/P ratio of 200, the maximal biomass, lipid and DHA yield in YTH medium reached 50.60, 24.44 and 10.85 g/L, respectively, which were much higher than those produced with glucose and fructose. Antioxidant capacity and enzyme activity analysis showed that the superior fermentation performance using YTH was mainly attributed to the significant increase in the activities of related key lipogenic enzymes, the reduction in intracellular reactive oxygen species and the inhibition of lipid peroxidation. Therefore, yacon tuber was proven to be an ideal alternative feedstock for efficient high-value DHA production by Schizochytrium sp.