Lignin Interaction with Cellulase during Enzymatic Hydrolysis

The conversion of lignocellulosic biomass into biofuels or biochemicals typically involves a pretreatment process followed by the enzyme-catalyzed hydrolysis of cellulose and hemicellulose components to fermentable sugars.Many factors can contribute to the recalcitrance of biomass,e.g.,the lignin content and structure,crystallinity of cellulose,degree of fiber polymerization,and hemicellulose content,among others.However,nonproductive binding between cellulase and lignin is the factor with the greatest impact on enzymatic hydrolysis.To reduce the nonproductive adsorption of enzymes on lignin and improve the efficiency of enzymatic hydrolysis,this review comprehensively summarized the progress that has been made in understanding the interactions between lignin and enzymes.Firstly,the effects of pretreatment techniques on lignin content and enzymatic hydrolysis were reviewed.The effects of lignin content and functional groups on enzymatic hydrolysis were then summarized.Methods for the preparation and characterization of lignin films were assessed.Finally,the methods applied to characterize the interactions between lignin and cellulase were reviewed,and methods for decreasing the nonproductive binding of enzymes to lignin were discussed.This review provides an overview of the current understanding of how lignin hinders the enzymatic hydrolysis of lignocellulosic biomass,and provides a theoretical basis for the development of more economical and effective methods and additives to reduce the interaction of lignin and enzymes to improve the efficiency of enzymatic hydrolysis.

Preparation of Aminated Lignin through Etherification and Amination

A new method for the preparation of aminated lignin （AEL） through etherification and amination reaction was presented. Chlorine atoms were ？rstly introduced into lignin through its etheri？cation with epichlorohydrin. Then, hydrophilic amine groups were grafted to the modi？ed lignin structure through amination with ethylenediamine to obtain AEL. Subsequent acidi？cation of AEL led to the ionized aminated lignin （IAEL）. The results of our analyses showed that the nitrogen content of AEL was 6.9%. Foaming and emulsifying experiments indicated that AEL had better foamability and emulsifying properties than IAEL. Surface tension tests showed that AEL and IAEL had similar critical micelle concentration （CMC）. However, IAEL had lower surface tension （36.33 mN/m） than AEL （42.89 mN/m） at CMC. These results demonstrate the promising applicability of AEL as an emulsi？er and that of IAEL as feedstock in the production of detergent and dispersant.