Comparative Evaluation of Adsorption of Major Enzymes in a Cellulase Cocktail Obtained from Trichoderma reesei onto Different Types of Lignin.

Dae-Seok Lee,Hyeun-Jong Bae,Younho Song,Yoon-Gyo Lee

doi:10.3390/polym14010167

Abstract

Cellulase adsorption onto lignin decreases the productivity of enzymatic hydrolysis of lignocellulosic biomass. Here, adsorption of enzymes onto different types of lignin was investigated, and the five major enzymes—cellobiohydrolases (CBHs), endoglucanase (Cel7B), β-glucosidase (Cel3A), xylanase (XYNIV), and mannanase (Man5A)—in a cellulase cocktail obtained from Trichoderma reesei were individually analyzed through SDS-PAGE and zymogram assay. Lignin was isolated from woody (oak and pine lignin) and herbaceous (rice straw and kenaf lignin) plants. The relative adsorption of CBHs compared to the control was in the range of 14.15–18.61%. The carbohydrate binding motif (CBM) of the CBHs contributed to higher adsorption levels in oak and kenaf lignin, compared to those in pine and rice lignin. The adsorption of endoglucanase (Cel7B) by herbaceous plant lignin was two times higher than that of woody lignin, whereas XYNIV showed the opposite pattern. β-glucosidase (Cel3A) displayed the highest and lowest adsorption ratios on rice straw and kenaf lignin, respectively. Mannanase (Man5A) was found to have the lowest adsorption ratio on pine lignin. Our results showed that the hydrophobic properties of CBM and the enzyme structures are key factors in adsorption onto lignin, whereas the properties of specific lignin types indirectly affect adsorption.

Highlights

Published: 1 January 2022Lignocellulosic biomass is considered an alternative to petroleum as an energy resource and is used to obtain bioconversion products for subsequent biochemical and/or energy production [1]
Lignocellulose is composed of three major polymers: lignin, hemicellulose, and cellulose
Cel3A has been characterized to have a higher isoelectric point (8.5) and hydrophobicity value (−0.163) than those of Cel3B (5.73 and −0.317, respectively) [41]. These results indicate that Cel3A was to have the highest hydrophobicity patch score compared to serum albumin, Cel7A, Axe1, E1, XynA, sulted in lower cellulose consumption and a higher glucose yield in the fraction of the

Summary

Introduction

Lignocellulosic biomass is considered an alternative to petroleum as an energy resource and is used to obtain bioconversion products for subsequent biochemical and/or energy production [1]. The structural complexity of lignocellulose and its recalcitrance to degradation by hydrolytic enzymes reduces saccharification efficiency, and increase the costs to improve bioconversion rate, which, in turn, reduces the price competitiveness of the bioconversion products. The presence of lignin hinders enzymatic hydrolysis of lignocellulose. Two major factors contribute to the negative impact of lignin on hydrolysis. The first factor is the structural recalcitrance of lignocellulose due to lignin. Lignocellulose is composed of three major polymers: lignin, hemicellulose, and cellulose. Lignin is a highly oxygenated aromatic polymer and binds cellulose microfibrils comprised of β-1,4-D-glucose polysaccharide chain bundles, ranging from 10 to 35 nm in diameter, together with a hemicellulose linker

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