高效木聚糖降解酶系定制的新进展与挑战

木聚糖是植物细胞壁中含量最丰富的非纤维素多糖,大约占陆地生物质资源的20%-35%。不同物种来源的木聚糖结构因取代方式不同而具有广泛的异质性,这对生物质资源向生物燃料和其他高值产品高效转化提出了重大挑战。因此,需要开发由不同类型酶组成的最佳混合物以有效糖化木聚糖类底物。但是针对特定类型的底物设计高效降解酶系十分困难,应考虑底物的类型、底物的组成和物理性质、多糖的聚合度以及不同降解酶组分的生化性质等。本文从不同植物木聚糖的结构异质性与合成复杂性方面展示了其抗降解屏障,同时介绍了木聚糖主链降解酶系及侧链降解酶系的多样性以及协同降解作用,综述了复杂生境中微生物种群产生的混合酶系、降解菌株产生的高效酶系,以及基于特定木聚糖底物改造并定制简化高效的酶系统。随着不同种类木聚糖精细结构和木聚糖降解酶底物特异性的深入研究,针对特定底物类型进行绿色高效木聚糖酶系定制,加速木聚糖类底物的降解,从而实现木质纤维素资源的绿色高值化利用。

New advances and challenges in customizing xylan-degrading enzymes

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.