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.
Highlights
Xylanase is one of the most extensively used biocatalysts for biomass degradation
A single band was observed for all enzymes after treatment with endo-β-Nacetylglucosaminidase H (Endo H), which corresponded to the theoretical molecular weight (Additional file 1: Figure S2)
Xylanases used in biomass degradation need to possess high catalytic efficiency and excellent thermostability
Summary
Xylanase is one of the most extensively used biocatalysts for biomass degradation. its low catalytic efficiency and poor thermostability limit its applications. Improving the properties of xylanases to enable synergistic degradation of lignocellulosic biomass with cellulase is of considerable significance in the field of bioenergy. Biomass is considered to be among the most promising renewable energy sources due to its energyrich reserves and low cost of production [2]. Lignocellulosic materials, such as agricultural residues, are mainly composed of cellulose, hemicellulose, and other minor components. Due to its heterogeneous structure, the degradation of xylan requires several types of backbone and sidechain-cleaving enzymes. Xylanases are crucial enzymes that catalyze the hydrolysis of xylan backbones, and have widespread applications in animal feed, food, bioethanol, detergent, and paper pulp industries [5, 6]
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