Comprehensively Understanding Enzymatic Hydrolysis of Lignocellulose and Cellulase–Lignocellulose Adsorption by Analyzing Substrates’ Physicochemical Properties

Abstract

In order to understand the relationship among enzymatic hydrolysis of lignocellulose, cellulase adsorption characteristics, and physicochemical properties of lignocellulose, a series of investigations was conducted, including composition, surface morphology, chemical bonds, functional groups, pore characteristics, cellulase accessibility, productive cellulase adsorption, cellulase adsorption isotherm, and kinetics of sodium hydroxide (NaOH) and ammonia-treated sugarcane bagasse (SCB) substrates. The results showed that the hydrolysis efficiency of NaOH-treated SCB (87.85%) was higher than that of ammonia-treated SCB (33.65%) and NaOH-treated SCB had less lignin, looser surface, and larger specific surface area and pore volume. This suggested that better accessibility of NaOH-treated SCB to cellulase resulted in higher enzymatic hydrolysis efficiency. The data on cellulase adsorption showed that NaOH-treated SCB had more productive adsorption, less non-productive adsorption, better adsorption capacity, and smaller binding strength with cellulase, which was also beneficial to the enhancement of enzymatic hydrolysis of NaOH-treated SCB. In addition, it was found that once cellulase molecules were adsorbed onto these two SCB substrates, two types of bonds as follows might be formed: one was C-OR (R means organic groups) and the other was C-OH··NH that was a type of hydrogen bond formed between the hydrogen of amino group in cellulase and the hydroxyl group in lignocellulose. This study would help further learn the link between lignocellulosic substrate characteristics and enzymatic hydrolysis or cellulase adsorption properties of lignocellulose.