Optimization of an artificial cellulase cocktail for high-solids enzymatic hydrolysis of cellulosic materials with different pretreatment methods

Optimization of the composition of cellulase mixtures is an effective strategy to improve their hydrolytic efficiency and reduce protein demand during enzymatic degradation of lignocelluloses. In this study, the mixture design method was used to optimize the ratios of endoglucanase II (EG II), cellobiohydrolase I (CBH I) and beta-glucosidase I (BG I) from Penicillium oxalicum in an artificial cellulase mixture for the hydrolysis of six different cellulosic materials. The optimal composition of enzyme mixture was distinctly different among not only cellulosic materials with different pretreatment methods but hydrolyses at different solids concentrations. CBH I was most critical for the hydrolysis of two acid-pretreated materials, probably due to its strong adsorption on lignin. A higher proportion of EG II was needed for the hydrolysis of ammonium sulfite pretreated wheat straw. The requirements of specific cellulase components were more pronounced at high solids concentrations, highlighting the importance of considering solids loading when optimizing cellulase cocktails.