Linares-Pasten Javier A, Aronsson Anna, Karlsson Eva Nordberg
Biotechnology, Department of Chemistry, Lund University, Lund, Sweden.
Curr Protein Pept Sci. 2018;19(1):48-67. doi: 10.2174/1389203717666160923155209.
Xylooligosaccharides (XOS) have gained increased interest as prebiotics during the last years. XOS and arabinoxylooligosaccharides (AXOS) can be produced from major fractions of biomass including agricultural by-products and other low cost raw materials. Endo-xylanases are key enzymes for the production of (A)XOS from xylan. As the xylan structure is broadly diverse due to different substitutions, diverse endo-xylanases have evolved for its degradation. In this review structural and functional aspects are discussed, focusing on the potential applications of endo-xylanases in the production of differently substituted (A)XOS as emerging prebiotics, as well as their implication in the processing of the raw materials. Endo-xylanases are found in at least eight different glycoside hydrolase families (GH), and can either have a retaining or an inverting catalytic mechanism. To date, it is mainly retaining endo-xylanases that are used in applications to produce (A)XOS. Enzymes from these GH-families (mainly GH10 and GH11, and the more recently investigated GH30) are taken as prototypes to discuss substrate preferences and main products obtained. Finally, the need of new and accessory enzymes (new specificities from new families or sources) to increase the yield of different types of (A)XOS is discussed, along with in vitro tests of produced oligosaccharides and production of enzymes in GRAS organisms to facilitate use in functional food manufacturing.
在过去几年中，低聚木糖（XOS）作为益生元越来越受到关注。低聚木糖和阿拉伯木聚糖低聚糖（AXOS）可以从包括农业副产品和其他低成本原料在内的大部分生物质中生产出来。内切木聚糖酶是从木聚糖生产（A）XOS的关键酶。由于木聚糖结构因不同取代基而广泛多样，因此进化出了多种内切木聚糖酶来降解它。在这篇综述中，我们讨论了内切木聚糖酶的结构和功能方面，重点关注内切木聚糖酶在生产不同取代的（A）XOS作为新兴益生元方面的潜在应用，以及它们在原材料加工中的作用。内切木聚糖酶至少存在于八个不同的糖苷水解酶家族（GH）中，其催化机制可以是保留型或转化型。迄今为止，在生产（A）XOS的应用中主要使用的是保留型内切木聚糖酶。来自这些GH家族（主要是GH10和GH11，以及最近研究的GH30）的酶被用作原型来讨论底物偏好和获得的主要产物。最后，讨论了需要新的和辅助酶（来自新家族或新来源的新特异性）来提高不同类型（A）XOS的产量，以及对所生产的低聚糖进行体外测试和在公认安全的生物体中生产酶以促进其在功能性食品制造中的应用。
