High solids loading conversion of corn stover for lipid production by Rhodosporidium toruloides

Abstract

The conversion of lignocellulosic biomass (LCB) at high solids loading is economically viable; nonetheless, it presents difficulties for hydrolytic enzymes and microbial cells because of increased sugar levels, other by-products, and high viscosity. In the current study, alkaline storage pretreated corn stover (AS-CS) received upon treatment with sodium hydroxide (NaOH) was utilized, and a squeezing process was employed to remove alkaline black liquid (ABL) from the steamed AS-CS slurry. Total reducing sugar (TRS) recoveries from AS-CS were 84%, 89%, and 100% at NaOH loadings of 2%, 4%, and 6%, respectively. The squeeze process removed 75–80% of the ABL while obtained hydrolysates with lower viscosity and fewer inhibitors. Rhodosporidium toruloides exhibited robust growth on AS-CS hydrolysates with ABL removed, even at solids loading of up to 40%. However, the same strain failed to grow when exposed to non-squeezed AS-CS hydrolysates with solids loading exceeding 10%. When using AS-CS hydrolysates at 20% solids loading with ABL removed, a lipid yield of 0.19 g/g TRS was obtained. The economic viability of ABL removal for large-scale LCB conversion should be the focus of future research.