Enhanced Bioconversion in Herbaceous Feedstocks from Impregnation of Co-Catalytic Lewis Acid and Deacetylation and Mechanical Refining

Improvements in conversion processes are needed to further reduce process complexity, biorefinery capital and operating (CAPEX/OPEX) costs, lower enzyme usage. Previous work has demonstrated that deacetylation and mechanical refining (DMR) process effectively deconstructs herbaceous biomass while producing highly digestible lignocellulosic slurries, with high titers of monomeric sugars, at reduced enzyme loadings (Poster 553 Chen at al,). We evaluated a co-catalytic approach using three Lewis acids: Fe+2, Fe+3, and Al+3, in sulfate form, at 1 mM, 5 mM and 10 mM concentrations. Lewis acids were impregnated into corn stover, followed by deacetylation with NaOH, and mechanically refined, prior to enzymatic hydrolysis (EH). Lower concentrations of Lewis acid positively impacted EH yield, increasing concentration lowered EH yield. Likewise Lewis acid treatment was more effective when combined with deacetylation than with deacetylation or Lewis acid treatment, alone. Comparing the effectiveness of the three Lewis acids identified ferrous iron more effective than ferric or aluminum (Fe+2 > Fe+3> Al+3) sulfate. Enzymatic hydrolysis sugar (glucose and xylose) concentration was higher 8% and 13%, respectively, in Fe2+ impregnated corn stover compared to the control. Refining energy required for PFI milling was reduced by ~25% with Fe+2 impregnation. However, treatment with Fenton treatment of the Fe2+ impregnated, deacetylated and PFI milled corn stover resulted in lower yields. for monomeric glucose and xylose due to non-specific degradation of carbohydrates and lignin.