Structural Considerations on the Use of Endo-Xylanases for the Production of prebiotic Xylooligosaccharides from Biomass

Abstract

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 substi-tutions, 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 dif-ferently 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 specifici-ties 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 fa-cilitate use in functional food manufacturing.

Characterization of a novel xylanase from Aspergillus flavus with the unique properties in production of xylooligosaccharides

“…Actually, the most common XOs produced by enzymatic hydrolysis from previously reported endo‐xylanases are X2 and X3 . Interestingly, the endo‐xylanase AfXynB that we described herein exhibited a new hydrolytic property compared to the other reported endo‐xylanases, and it could hydrolyze the beechwood xylan to only yield X2 and X5.…”

Electrospray multistage mass spectrometry in the negative ion mode for the unambiguous molecular and structural characterization of acidic hydrolysates from 4‐O‐methylglucuronoxylan generated by endoxylanases

“…Xylan‐derived hydrolysates have already found commercial applications (ethanol, xylitol, and xylo‐oligosaccharides) . XOSs, including arabinose‐substituted XOSs and acidic XOSs containing MeGlcA substituents, have recently gained interest as prebiotics …”

Galactomannan from Trigonella foenum‐graecum L. seed: Prebiotic application and its fermentation by the probiotic Bacillus coagulans strain MTCC 5856

“…Later, Hutkins et al in 2016 defined prebiotics as "food ingredients that help support growth of probiotic bacteria" or "nondigestible substances that act as food for the gut microbiota" (Hutkins et al, 2016). There are prebiotic compounds such as galactooligosaccharide and inulin and the dietary fibers such as resistant starch, pectin, beta-glucans, and xylooligosaccharides that qualify for the prebiotics definition (Linares-Pastén, Aronsson, & Nordberg, 2017;Roberfroid, 2007;Zaman & Sarbini, 2015). Prebiotics confer the benefits by supporting the growth of probiotics in the colon by serving as a substrate.…”