Structural characterization of the lignin-carbohydrate complex in biomass pretreated with Fenton oxidation and hydrothermal treatment and consequences on enzymatic hydrolysis efficiency

In this study, lignin-carbohydrate complexes (LCCs) were isolated from biomass (raw and pretreated) to investigate the structural changes in biomass pretreated by Fenton oxidation and hydrothermal treatment, and their effect on enzymatic hydrolysis. The composition and structure of the LCCs fractions were investigated via carbohydrate analysis, XRD, FT-IR, and 2D HSQC NMR. The biomass degradation rate of yellow poplar and larch during Fenton oxidation and hydrothermal treatment was approximately 30%. Most of the hemicellulose was degraded during pretreatment, while xylan remained in the yellow poplar, and galactan, mannan, and xylan remained in the larch. The fractional yield of glucan-rich LCC (LCC1) in the yellow poplar (raw and pretreated biomass) was high, while that of glucomannan-rich LCC (LCC3) in larch was higher than the yield yellow poplar. Phenyl glycoside, gamma-ester, and benzyl ether linkages were observed in the LCCs of yellow poplar, while phenyl glycoside and gamma-ester were detected in those of larch. Following pretreatment, the frequencies of beta-beta ', beta-5, and gamma-ester in the LCCs of larch were found to be higher than in those of yellow poplar. The efficiencies of enzymatic hydrolysis for the pretreated yellow poplar and larch were 93.53% and 26.23%, respectively. These finding indicated that the beta-beta ', beta-5, and gamma-ester linkages included in the pretreated biomass affected the efficiency of enzymatic hydrolysis.

Automated summary

This study investigated lignin-carbohydrate complexes (LCCs) isolated from raw and pretreated biomass to study the structural changes during Fenton oxidation and hydrothermal treatment and their impact on enzymatic hydrolysis. It was found that yellow poplar and larch showed different degradation rates and LCCs compositions during pretreatment, affecting the efficiency of enzymatic hydrolysis, with β-β', β-5, and γ-ester linkages playing a significant role.