(757a) Effects of Inhibitory Compounds in Lignocellulosic Hydrolysate on Rhodotorula Glutinis Growth and Lipid Accumulation

Microbial lipophilic compounds, referred to as single-cell oils (SCO), are of potential industrial interest due to their triacylglycerol structure, which can be used as biodiesel feedstock. The utilization of pulp and paper wastewater as fermentation media and lignocellulosic hydrolysate as a substrate for cultivation of the oleaginous yeast Rhodotorula glutinis has been investigated for the efficient single-cell oil (lipid) production. Our previous studies indicated that the oleaginous yeast R. glutinis could utilize a mixture of glucose and xylose in pulp and paper wastewater and produce lipids efficiently, which implies a potential utilization of lignocellulosic substrates. For the purpose of bioconversion of lignocellulosic biomass into lipids, the cellulose and hemicelluloses must be broken down into reducing sugars such as glucose and xylose. However, the depolymerization of cellulose and hemicellulose results in the production of inhibitory byproducts that can considerably decrease the fermentability of lignocellulosic hydrolysates. In this study, the synthetic lignocellulosic hydrolysate was used as a substrate for the sustainable production of microbial lipids as biodiesel feedstock by the oleaginous yeast Rhodotorula glutinis. Lignocellulosic hydrolysate was added to the wastewater media to obtain high C/N ratio for enhanced lipid production. The effects of three representative lignocellulose inhibitors including furfural, 5-hydroxymethylfurfural, and acetic acid on the growth and lipid accumulation of R. glutinis were studied. The synergetic effect of inhibitors was investigated and the tolerance level of R. glutinis was evaluated. The effect of inhibitors on fatty acid composition of storage lipid was then determined in order to evaluate the suitability of the microbial oil feedstock for biodiesel production.