Addressing two major limitations in high-solids enzymatic hydrolysis by an ordered polyethylene glycol pre-incubated strategy: Rheological properties and lignin adsorption for enzyme

Substrate-specific responses to mixing conditions in high-solids enzymatic hydrolysis: Insights from microcrystalline cellulose and dilute-acid pretreated corncob

This study investigates the mixing effects on the enzymatic hydrolysis of microcrystalline cellulose (MCC) and dilute-acid pretreated corncob substrates under high-solid conditions. Enzymatic hydrolysis experiments were conducted to assess cellulose conversion rates under varying mixing conditions (0, 50, 150, and 250 rpm) and solids loadings (5 %, 15 %, 25 %, and 35 %, w/v), and distinct physicochemical properties of the substrates were characterized. Additionally, the role of mixing conditions and solid loadings on cellulose hydrolysis kinetics and enzyme adsorption on both substrates and lignin were elucidated. Results demonstrated that both substrates exhibited a decrease in cellulose conversion as solid loading increased, with dilute-acid pretreated corncob consistently showing higher conversion rates compared to MCC. Kinetic analysis revealed that both the rate constant k and the fractal exponent h increased with mixing intensity; however, the increase was more pronounced for dilute-acid pretreated corncob's k and MCC's h. Enzyme adsorption studies indicated dilute-acid pretreated corncob had a higher adsorption capacity qmax and a weaker binding affinity K compared to MCC. Furthermore, increased mixing enhanced enzyme adsorption qmax while decreasing binding affinity K, with more pronounced effects on dilute-acid pretreated corncob's qmax and MCC's K. Lower mixing intensities favored cellulase-lignin binding, with an optimal cellulase-to-lignin binding ratio of approximately 1:1.3, suggesting a more stable interaction. These findings underscore the critical role of substrate disparities in high-solid enzymatic hydrolysis, offering valuable guidance for optimizing mixing strategies for efficient conversion of lignocellulosic biomass.

Quantitative correlation analysis between particle liquefaction and saccharification through dynamic changes of slurry rheological behavior and particle characteristics during high-solid enzymatic hydrolysis of sugarcane bagasse

This study identified the intrinsic relationships among slurry rheology, particle characteristics, and lignocellulosic liquefaction/saccharification based on correlation analysis and principal component analysis during the hydrolysis of sugarcane bagasse pretreated by deep eutectic solvents (DES) and mechanical milling (MM). The DES-MM pretreated lignocellulosic slurry (20% solids) exhibited high apparent viscosity of 1.4 × 104 Pa·s and shear stress of 929.0 Pa under steady state. Glucose production had a negative linear correlation with slurry viscosity (R2, 0.69-0.97), whereas its correlation with yield stress (R2, 0.85-0.98) depended on the particle liquefaction rate. The availability of free water provided a major contribution to improving slurry rheology. However, the size reduction of submillimeter particles and the changes in particle hydrophilicity during liquefaction were not significantly correlated with rheological changes. Various interrelated particle characteristics and rheological changes were integrated into two simple principal variables to predict glucose production with a high R2 of 0.96.