Understanding the effects of different residual lignin fractions in acid-pretreated bamboo residues on its enzymatic digestibility

Publication year: 2021
Authors: Wenqian Lin 1, Jinlai Yang 2, Yayue Zheng 1, Caoxing Huang 1, Qiang Yong 1
Affiliations:

1 - Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing, 210037, China
2 - China National Bamboo Research Center and Key Laboratory of High Efficient Processing of Bamboo of Zhejiang Province, Hangzhou, 310012, Zhejiang, China

Published in: Biotechnology for Biofuels, 2021, Vol. 14, Article number: 143 (2021)
doi: 10.1186/s13068-021-01994-y

Background

During the dilute acid pretreatment process, the resulting pseudo-lignin and lignin droplets deposited on the surface of lignocellulose and inhibit the enzymatic digestibility of cellulose in lignocellulose. However, how these lignins interact with cellulase enzymes and then affect enzymatic hydrolysis is still unknown. In this work, different fractions of surface lignin (SL) obtained from dilute acid-pretreated bamboo residues (DAP-BR) were extracted by various organic reagents and the residual lignin in extracted DAP-BR was obtained by the milled wood lignin (MWL) method. All of the lignin fractions obtained from DAP-BR were used to investigate the mechanism for interaction between lignin and cellulase using surface plasmon resonance (SPR) technology to understand how they affect enzymatic hydrolysis

Results

The results showed that removing surface lignin significantly decreased the yield for enzymatic hydrolysis DAP-BR from 36.5% to 18.6%. The addition of MWL samples to Avicel inhibited its enzymatic hydrolysis, while different SL samples showed slight increases in enzymatic digestibility. Due to the higher molecular weight and hydrophobicity of MWL samples versus SL samples, a stronger affinity for MWL (KD = 6.8–24.7 nM) was found versus that of SL (KD = 39.4–52.6 nM) by SPR analysis. The affinity constants of all tested lignins exhibited good correlations (r > 0.6) with the effects on enzymatic digestibility of extracted DAP-BR and Avicel.

Conclusions

This work revealed that the surface lignin on DAP-BR is necessary for maintaining enzyme digestibility levels, and its removal has a negative impact on substrate digestibility.

 


MP-SPR keywords: Au sensor slide, interaction mechanism, protein-polymer interaction, spin-coated sensors