Analysis of metabolic fluxes for better understanding of mechanisms related to lipid accumulation in oleaginous yeast Trichosporon cutaneum

Microbial fermentation for producing biodiesel from lignocellulosic hydrolysates is receiving increasing attention and attempts have been made to screen an oleaginous Trichosporon sp. with high lipid content and a strong tolerance to lignocellulose hydrolysates. In order to better understand mechanisms related to its lipid accumulation, metabolic flux analysis was performed under 5 g L−1 ammonium sulfate (high nitrogen) and/or 0.4 g L−1 ammonium sulfate (low nitrogen) conditions. Cell growth phase and lipid accumulation phase were shown for cells grown under low nitrogen condition. Results of flux distribution demonstrated that NADPH provided by cytosolic malic enzyme and the acetyl-CoA from cytoplasmic citrate by the ATP: citrate lyase were the two primary sources for excess lipid accumulation. Flux data also supported the fact that the citrate pyruvate cycle plays an essential role in the lipid accumulation. The flux information obtained could also motivate new design strategies for oleaginous yeasts for enhanced biodiesel production.