Investigation of the effect of lignin/pseudo-lignin on enzymatic hydrolysis by Quartz Crystal Microbalance

Abstract

During acidic pretreatments, both lignin and pseudo-lignin tend to form aggregated droplets on the surface of cellulose and further inhibit its enzymatic digestibility. However, the interaction performance between pseudo-lignin and enzymes is still obscure. In this work, acid pretreated bamboo residues (AP-BR) were extracted with 1, 4-dioxane to remove these droplets, which decreased the lignin content and increased the glucose yield from 16.3 % to 23.0 %. To further investigate these droplets on the enzymatic hydrolysis, the adsorption capability of pseudo-lignin and residual lignin on the enzymes were measured by quartz crystal microgravimetry with dissipation monitoring. The results indicated that pseudo-lignin has similar adsorption capability to enzymes as lignin in the fast adsorption process, but residual lignin in AP-BR (PMWL) and pseudo-lignin generated from glucose (GPL) take longer time in slow adsorption process than the pseudo-lignin generated from xylose (XPL). Besides, lignin showed faster desorption capability than pseudo-lignin. It is also interesting to find that lignin and pseudo-lignin exhibited lower adsorption capability toward enzymes than cellulose. According to the dynamics of enzymatic hydrolysis, when pseudo-lignin and lignin were mixed with cellulose, the maximum amount of products could be reduced and it would take longer time to reaching the maximum enzymatic hydrolysis efficiency than neat cellulose. This work provides an insight into how the pseudo-lignin /lignin droplets affect the enzymatic digestibility of pretreated biomass.