Direct enzymatic hydrolysis of alkaline storage pretreated corn stover for lipid production by Rhodosporidium toruloides

Abstract

Lignocellulosic biomass (LCB) conversion often requires chemical and energy-intensive pretreatment, which produces toxic by-products that impede microbial cell growth and downstream processes. Thus, pretreatment under mild conditions remains to be developed to improve enzymatic digestibility and reduce degradation products. Here, we investigated the direct enzymatic hydrolysis of alkaline storage pretreated corn stover (AS-CS) that was treated with different concentrations of sodium hydroxide (NaOH) under various temperatures for different storage duration. Results revealed that AS-CS was suitable for direct enzymatic hydrolysis for high sugar recovery. The total reducing sugar (TRS) recovery reached 88% for the CS sample treated with 6% NaOH for 60 days at 15 °C, and the corresponding hydrolysates were successfully used by Rhodosporidium toruloides for lipid production at a lipid yield of 0.20 g/g consumed TRS. Storage temperatures ranged from 15 to 35 °C had no differential impacts on enzymatic digestibility, however at 25 °C, the control and those CS samples treated with 2% NaOH were found with relatively high microbial contamination. This method offers an energy-efficient LCB conversion for high TRS recovery and supports microbial lipid technology. Future studies should focus on scalability and techno-economic analysis to validate its applicability on a larger scale.