With the rapid depletion of crude resources, microorganism lipids have started attracting increasing attention because of their renewable qualities. However, their production is limited by high costs. In this study, we aimed to reduce the production cost of Sporidiobolus pararoseus JD-2 lipid by co-producing extracellular polysaccharide (EPS) and single-cell protein (SCP). In batch fermentation, the yields of lipid, EPS and SCP under ammonia nitrogen limitation increased by 20.3%, 32.0% and 43.7%, respectively, compared with the yields in the control group (without NH4+). Next, fed-batch fermentation was performed under different ammonia nitrogen levels. The yield, productivity and coefficient of lipid reached 47.1 ± 1.1 g/L, 0.66 g/L/h and 0.250 g/g, respectively, under an ammonia nitrogen level of 20 g/L (NH4)2SO4. In the same process, 14.3 ± 1.6 g/L EPS and 12.7 ± 0.8 g/L SCP were also obtained. Nutrient analysis of the product revealed that NH4+ affected the proportion of pigments in the carotenoids and increased the content of unsaturated fatty acids in the lipid; EPS mainly comprised galactose, glucose, mannose and fucose, at a ratio of approximately 45:37:2:1; and the essential amino acid content in SCP accounted for 48% of the product. Thus, this study provided a new strategy for improving S. pararoseus JD-2 lipid production at a lower cost.
Keywords: Ammonia nitrogen-limited; Exopolysaccharide; Microbial lipid; Single-cell protein; Sporidiobolus pararoseus JD-2.