Modeling and design of fed-batch strategies for achieving 255 g/L sugar concentration from high-solid enzymatic hydrolysis of pretreated corn stover

Abstract

Achieving high sugar concentrations through enzymatic hydrolysis of pretreated lignocellulose with low enzyme loadings is crucial for reducing the costs of lignocellulosic biorefineries. However, the adverse effects of the “solid effect” pose essential challenges in this regard. In this study, the objective is to improve the sugar concentrations through enzymatic hydrolysis of Densifying Lignocellulose with Ca(OH)2 or H2SO4 followed by Autoclave pretreated corn stover (DLCA(ch)-CS or DLCA (sa)-CS) at 40 % w/w solid loading through kinetic analysis and a statistically designed fed-batch feeding strategy. Initially, the hydrolysis kinetics of different pretreated biomass were analyzed using fractal kinetic modeling, aiming to elucidate the reasons for the observed differences in hydrolysis. Furthermore, leveraging the kinetic differences, the optimal initial solid loading was determined, and statistical models were employed to optimize feeding modes for enzymatic hydrolysis. The result revealed that compared with H2SO4, Ca(OH)2 serves as an better catalyst for improving the hydrolysability of biomass, enhancing cellulose accessibility to cellulases and reduce the mass transfer rate during enzymatic hydrolysis. Interestingly, the optimal feeding mode for less digestible substrate (DLCA(sa)-CS) is different from the more digestible substrate (DLCA(ch)-CS). Notably, by using the optimized fed-batch feeding mode, the sugar concentration can reach a maximum of 255 g/L, with glucan conversion of 89.8 %, at low enzyme loading (10 mg protein/g glucan). This is the highest total sugar concentration achieved through 72 h enzymatic hydrolysis with low enzyme loadings using a fed-batch strategy. This approach proves highly effective in designing fed-batch strategies for pretreated biomass and has great potential to serve as a universal tool for designing suitable feeding schemes for various bionconversion process.