One-pot biorefining of ionic liquid-pretreated corn stover and peanut shell using in-house prepared lignocellulolytic enzymes

This study combined corn stover (CS) and peanut shell (PS) as a carbon source for Bacillus sp. BC-005 to produce lignocellulose-degrading enzymes. All major effective enzyme production factors, i.e., time (0–120 h), nitrogen sources, temperature (30–60 °C), pH (4–12), inducers (glucose, xylose, CMC, starch, sucrose), surfactants (Tween 20, polyethylene glycol, Triton-X), and biomass pretreatment with ionic liquid (IL), were optimized. These enzymes operated effectively at pH 4–12 and 30–50 °C. The optimal enzyme production was achieved when the culture was grown on IL-pretreated biomass at pH 9.0 and 50 °C for 72 h in the presence of polyethylene glycol. After optimizing enzyme production, IL pretreatment, hydrolysis, and ethanol production were conducted into a single-pot. Applying these enzymes to IL-pretreated biomass yielded 122.4 g/L and 109.6 g/L fermentable sugars from CS and PS, respectively. However, ethanol production was limited in the presence of ILs, resulting in 28.4 and 27.3 g/L ethanol (46.9 % and 49.2 % yields), respectively. Water-washing of the IL-pretreated biomass improved ethanol yields to 58.6 and 52.2 g/L (93.1 % and 92.4 % yields), respectively. The integrated approach of enzyme production and direct application in a single-step pretreatment and fermentation demonstrates high potential for large-scale application.