A Highly Glucose Tolerant \xdf-Glucosidase from Malbranchea pulchella (MpBg3) Enables Cellulose Saccharification

Lummy Maria Oliveira Monteiro,Marcos S Buckeridge,Maria De Lourdes Teixeira De Moraes Polizeli Polizeli,Rolf Alexander Prade,Ana Claudia Vici,Matheus Pinto Pinheiro,Richard John Ward,Paulo Ricardo Heinen,Arthur Henrique Cavalcante De Oliveira

doi:10.1038/s41598-020-63972-y

Abstract

β-glucosidases catalyze the hydrolysis β-1,4, β-1,3 and β-1,6 glucosidic linkages from non-reducing end of short chain oligosaccharides, alkyl and aryl β-D-glucosides and disaccharides. They catalyze the rate-limiting reaction in the conversion of cellobiose to glucose in the saccharification of cellulose for second-generation ethanol production, and due to this important role the search for glucose tolerant enzymes is of biochemical and biotechnological importance. In this study we characterize a family 3 glycosyl hydrolase (GH3) β-glucosidase (Bgl) produced by Malbranchea pulchella (MpBgl3) grown on cellobiose as the sole carbon source. Kinetic characterization revealed that the MpBgl3 was highly tolerant to glucose, which is in contrast to many Bgls that are completely inhibited by glucose. A 3D model of MpBgl3 was generated by molecular modeling and used for the evaluation of structural differences with a Bgl3 that is inhibited by glucose. Taken together, our results provide new clues to understand the glucose tolerance in GH3 β-glucosidases.

Highlights

Β-glucosidases catalyze the hydrolysis β-1,4, β-1,3 and β-1,6 glucosidic linkages from non-reducing end of short chain oligosaccharides, alkyl and aryl β-D-glucosides and disaccharides
The Bgls may act as cellulolytic enzymes that synergistically function by converting cellulose to glucose
The activities of cellobiohydrolases and endoglucanases are inhibited by the reaction product, Bgls can overcome this inhibition by the hydrolysis of cellobiose[10,11,12]

Summary

Introduction

Β-glucosidases catalyze the hydrolysis β-1,4, β-1,3 and β-1,6 glucosidic linkages from non-reducing end of short chain oligosaccharides, alkyl and aryl β-D-glucosides and disaccharides. They catalyze the ratelimiting reaction in the conversion of cellobiose to glucose in the saccharification of cellulose for secondgeneration ethanol production, and due to this important role the search for glucose tolerant enzymes is of biochemical and biotechnological importance. Bgls can be considered to be the rate-limiting factor in the conversion of cellulose to glucose in biomass saccharification Due to this important role, there is an increasing demand for the identification, production and characterization of new Bgls that retain their catalytic activity in the presence of glucose[15]. The objective of this study was the isolation of a glucose-tolerant GH3 β-glucosidase produced by M. pulchella together with the biochemical characterization and a structural study of this enzyme

Objectives

Methods

Results