Effect of Lignin Chemistry on the Enzymatic Hydrolysis of Woody Biomass

Abstract

The impact of lignin-derived inhibition on enzymatic hydrolysis is investigated by using lignins isolated from untreated woods and pretreated wood pulps. A new method, biomass reconstruction, for which isolated lignins are precipitated onto bleached pulps to mimic lignocellulosic biomass, is introduced, for the first time, to decouple the lignin distribution issue from lignin chemistry. Isolated lignins are physically mixed and reconstructed with bleached pulps. Lignins obtained from pretreated woods adsorb two to six times more cellulase than lignins obtained from untreated woods. The higher adsorption of enzymes on lignin correlates with decreased carbohydrate conversion in enzymatic hydrolysis. In addition, the reconstructed softwood substrate has a lower carbohydrate conversion than the reconstructed hardwood substrate. The degree of condensation of lignin increases significantly after pretreatment, especially with softwood lignins. In this study, the degree of condensation of lignin (0.02 to 0.64) and total OH groups in lignin (1.7 to 1.1) have a critical impact on cellulase adsorption (9 to 70%) and enzymatic hydrolysis (83.2 to 58.2%); this may provide insights into the more recalcitrant nature of softwood substrates.

Delignification of Lignocellulosic Biomass and Its Effect on Subsequent Enzymatic Hydrolysis

“…It is widely accepted that the removal of lignin by various delignification processes can enhance the enzymatic hydrolysis of lignocellulosic biomass by reducing physical and biochemical hindrances from lignin and by making pores more accessible for the effective mass transfer of enzymes (Yu et al 2011(Yu et al , 2014. The increase in carbohydrate conversion after delignification has also been confirmed in this study, but it will be necessary to explain the high carbohydrate conversion in oxygen-delignified HW samples, which still contain a considerable amount of lignin.…”

Lignin-based polyoxyethylene ether enhanced enzymatic hydrolysis of lignocelluloses by dispersing cellulase aggregates

“…As a result, the residual lignin acts as a physical barrier and an attractant to cellulase to reduce the adsorption of cellulase on cellulose (Kumar et al, 2012;Li et al, 2014;Selig et al, 2007). Hence, lignin has a significant negative impact on the enzymatic hydrolysis efficiency of lignocelluloses (Nakagame et al, 2011;Pan, 2008;Yu et al, 2014;Zeng et al, 2014).…”

Characteristics of Lignin Fractions from Dilute Acid Pretreated Switchgrass and Their Effect on Cellobiohydrolase from Trichoderma longibrachiatum

“…It is widely accepted that lignin inhibits enzymatic hydrolysis of lignocellulosic biomass (Zeng et al, 2014;Lu et al, 2016;Saini et al, 2016;Yang et al, 2016). The adsorption of enzymes onto isolated lignins from dilute acid or hot water pretreated biomass has been studied (Zheng et al, 2013;Yu et al, 2014;Li et al, 2016;Lu et al, 2016;Sun et al, 2016). They reported key lignin-enzyme binding effects including the effects of condensed phenolic OH groups, methoxy groups, and the degree of lignin condensation on cellulase binding.…”