Analysis of glucose inhibition characteristics during high-solids enzymatic hydrolysis of pretreated lignocellulose
Jingrui Liang, Jian Du, Xiujun Zhang, M. X. Liu, Yamin Zhang, Nannan Chen, Wenjie Sun, Jingxuan Nie, Mengxian Liang, Pinwen Wang, Xinyu He
Abstract
High-solids enzymatic hydrolysis is a key process for ensuring the economic feasibility of lignocellulose bioconversion. During enzymatic hydrolysis, the rate of cellulose conversion decreases markedly with increasing solids concentration, which is attributed to inhibition by soluble compounds. Thus, gaining insights into the inhibitory properties of these compounds is essential for reducing enzyme costs. During hydrolysis, glucose-induced inhibition accounted for more than 37 % of the total inhibitory effect after 24 h, and this inhibitory effect increased with time. The inhibitor-to-enzyme ratio was a critical factor influencing the extent of inhibition; however, cellulase was more sensitive to glucose inhibition at high concentrations. As such, glucose-induced inhibition could not be overcome by increasing enzyme loading within normal dosage ranges. Different enzyme components experienced varying degrees of inhibition, and the synergistic effects among these components were also considerably reduced. Glucose inhibition of endoglucanase II involved both competitive and noncompetitive modes, which included competitive binding of carbohydrate-binding modules to the substrate and overlapping binding sites on the catalytic channel of the catalytic domain. We propose that modifying these conflicting binding sites can reliably alleviate glucose inhibition. This study has implications for addressing severe enzyme inhibition and reducing costs in bioconversion processes at a commercial scale.