Effects of furfural and acetic acid on growth and lipid production from glucose and xylose by Rhodotorula glutinis

Microbial conversion of lignocellulosic sugars to triacylglycerols (a biodiesel or renewable diesel feedstock) was investigated using the oleaginous yeast Rhodotorula glutinis (ATCC 15125). In the shake flask experiments, R. glutinis was first grown in a nitrogen-rich medium utilizing an artificial acid hydrolysate of lignocellulosic biomass switchgrass as the sole carbon and energy source. Once the culture had reached the stationary phase, the cells were harvested and transferred to a fresh nitrogen-free media containing artificial acid hydrolysate sugars for lipid accumulation. Analysis of the data collected showed that the yeast were able to grow in the medium containing artificial acid hydrolysate sugars as the carbon and energy source. The net specific Growth rate(s) indicated that the presence of acetic acid and furfural in the artificial acid hydrolysate inhibited the growth of R. glutinis on glucose, but not the growth on xylose. The lipid accumulated in the cells, determined by gravimetrical method, increased from initial 4.3%–39.0% of dry cell mass weight. The major fatty acids of the accumulated lipids were palmitic acid, stearic acid, oleic acid, linoleic acid and γ-linoleic acid. These results indicate that it is feasible to convert the sugars in acid hydrolysate of lignocellulosic biomass to triacylglycerols using R. glutinis.