New advances and challenges in customizing xylan-degrading enzymes

Abstract:

Xylan is the most abundant non-cellulose polysaccharide in plant cell walls, accounting for about 20%?35% of terrestrial biomass resources. Xylan shows structural heterogeneity due to different substitution, which poses a major challenge for the conversion of biomass resources to biofuels and other value-added products efficiently. Therefore, it is necessary to develop optimal mixtures composed of different types of enzymes for efficient degrading xylan substrates. However, it is difficult to customize efficient degradation enzyme systems for specific types of substrates. The types of substrates, the composition and physical properties of substrates, the degree of polymerization of polysaccharides as well as the performance of different degrading enzyme components should be considered. This paper shows the recalcitrant barrier of plant xylan from structural heterogeneity and synthesis complexity. Moreover, the diversity of xylan degrading enzymes and their synergistic degradation are analyzed, as well as the mixed enzymes produced by microbial flora in nature habitats, the efficient enzyme system produced by degrading dominant microorganism, and the simplified efficient enzyme system modified and customized based on specific xylan substrates. With the deeper study on the fine structure of different types of xylan and the substrate specificity of the xylan-degrading enzymes, the green and efficient xylanase system was customized for specific substrate to accelerate the degradation of xylan substrate, so as to realize the friendly and high-value utilization of lignocellulosic resources.

Key words:Xylan, Structural heterogeneity, Xylan-backbone degradation enzymes, Xylan side-chain degradation enzymes, Synergistic degradation, customized enzymes