Improvement in catalytic activity and thermostability of a GH10 xylanase and its synergistic degradation of biomass with cellulase

Abstract

BackgroundXylanase is one of the most extensively used biocatalysts for biomass degradation. However, its low catalytic efficiency and poor thermostability limit its applications. Therefore, improving the properties of xylanases to enable synergistic degradation of lignocellulosic biomass with cellulase is of considerable significance in the field of bioenergy.ResultsUsing fragment replacement, we improved the catalytic performance and thermostability of a GH10 xylanase, XylE. Of the ten hybrid enzymes obtained, seven showed xylanase activity. Substitution of fragments, M3, M6, M9, and their combinations enhanced the catalytic efficiency (by 2.4- to fourfold) as well as the specific activity (by 1.2- to 3.3-fold) of XylE. The hybrids, XylE-M3, XylE-M3/M6, XylE-M3/M9, and XylE-M3/M6/M9, showed enhanced thermostability, as observed by the increase in the T50 (3–4.7 °C) and Tm (1.1–4.7 °C), and extended t1/2 (by 1.8–2.3 h). In addition, the synergistic effect of the mutant xylanase and cellulase on the degradation of mulberry bark showed that treatment with both XylE-M3/M6 and cellulase exhibited the highest synergistic effect. In this case, the degree of synergy reached 1.3, and the reducing sugar production and dry matter reduction increased by 148% and 185%, respectively, compared to treatment with only cellulase.ConclusionsThis study provides a successful strategy to improve the catalytic properties and thermostability of enzymes. We identified several xylanase candidates for applications in bioenergy and biorefinery. Synergistic degradation experiments elucidated a possible mechanism of cellulase inhibition by xylan and xylo-oligomers.

Improvement of XYL10C_∆N catalytic performance through loop engineering for lignocellulosic biomass utilization in feed and fuel industries

“…Corn stalk, wheat bran, and corn cob were soaked in 15% (w/w) aqueous ammonia at 60 °C for 24 h, as previously described [ 43 ]. Three lignocellulose biomass samples were soaked in 30 mL of phosphate buffer (pH 4.5, 0.01 mM) at a concentration of 5% (w/v), following which cellulase from Aspergillus niger [ 44 ] and/or xylanases were added.…”

“…The DS value was calculated using the following equation: where represents the content of reducing sugars produced in the reaction system when xylanase and cellulase were added simultaneously. and represent the quantity of reducing sugar when cellulase and xylanase are added during the hydrolysis process, respectively [ 43 ].…”

Structural and biochemical characterization of bifunctional XynA

“…In addition, XynA hydrolyzed corn stover pretreated with cellulase, showing an obvious synergistic effect (18). These unparalleled characteristics make XynA become an attractive candidate in biotechnology applications, such as bioenergy production and pulp processing (19)(20)(21). However, the xyanase activity of XynA is much stronger than its cellulase activity, which may raise some problems during application, for instance, the insufficient degradation of substrates and the quality control.…”

Structure-function relationship of bifunctional XynA

“…In addition, XynA hydrolyzed corn stover pretreated with cellulase, showing an obvious synergistic effect (Wang et al, 2019). These unparalleled characteristics make XynA become an attractive candidate in biotechnology applications, such as bioenergy production and pulp processing (Dhiman et al, 2014;Dodd & Cann, 2009;You et al, 2019). However, the xyanase activity of XynA is much stronger than its cellulase activity, which may raise some problems during application, for instance, the insufficient degradation of substrates and the quality control (Dodd & Cann, 2009).…”