endo-1,4-β-Xylanase (Cellvibrio japonicus)

endo-1,4-β-Xylanase (EC 3.2.1.8) is employed across a broad range of industries including animal feed, brewing, baking, biofuels, detergents and pulp (paper). Despite its importance, a rapid, reliable, reproducible, automatable assay for this enzyme that is based on the use of a chemically defined substrate has not been described to date. Reported herein is a new enzyme coupled assay procedure, termed the XylX6 assay, that employs a novel substrate, namely 4,6-O-(3-ketobutylidene)-4-nitrophenyl-β-4⁵-O-glucosyl-xylopentaoside. The development of the substrate and associated assay is discussed here and the relationship between the activity values obtained with the XylX6 assay versus traditional reducing sugar assays and its specificity and reproducibility were thoroughly investigated.

A range of α-L-arabinofuranosyl-(1-4)-β-D-xylo-oligosaccharides (AXOS) were produced by hydrolysis of wheat flour arabinoxylan (WAX) and acid debranched arabinoxylan (ADWAX), in the presence and absence of an AXH-d3 α-L-arabinofuranosidase, by several GH10 and GH11 β-xylanases. The structures of the oligosaccharides were characterised by GC-MS and NMR and by hydrolysis by a range of α-L-arabinofuranosidases and β-xylosidase. The AXOS were purified and used to characterise the action patterns of the specific α-L-arabinofuranosidases. These enzymes, in combination with either Cellvibrio mixtus or Neocallimastix patriciarum β -xylanase, were used to produce elevated levels of specific AXOS on hydrolysis of WAX, such as 3²-α-L-Araf-(1-4)-β-D-xylobiose (A³X), 2³-α-L-Araf-(1-4)-β-D-xylotriose (A²XX), 3³-α-L-Araf-(1-4)-β-D-xylotriose (A³XX), 2²-α-L-Araf-(1-4)-β-D-xylotriose (XA²X), 3²-α-L-Araf (1-4)-β-D-xylotriose (XA³X), 2³-α-L-Araf-(1-4)-β-D-xylotetraose (XA²XX), 3³-α-L-Araf-(1-4)-β-D-xylotetraose (XA³XX), 2³ ,3³-di-α-L-Araf-(1-4)-β-D-xylotriose (A²⁺³XX), 2³,3³-di-α-L-Araf-(1-4)-β-D-xylotetraose (XA²⁺³XX), 2⁴,3⁴-di-α-L-Araf-(1-4)-β-D-xylopentaose (XA²⁺³XXX) and 3³,3⁴-di-α-L-Araf-(1-4)-β-D-xylopentaose (XA³A³XX), many of which have not previously been produced in sufficient quantities to allow their use as substrates in further enzymic studies. For A^2,3XX, yields of approximately 16% of the starting material (wheat arabinoxylan) have been achieved. Mixtures of the α-L-arabinofuranosidases, with specific action on AXOS, have been combined with β-xylosidase and β-xylanase to obtain an optimal mixture for hydrolysis of arabinoxylan to L-arabinose and D-xylose.

The mucilage polysaccharides from Dioscorea opposita (DOMP) were extracted and treated with a single/dual enzymatic hydrolysis. The characterisation and viscosity were subsequently investigated in this study. DOMP obtained 62.52% mannose and 23.45% glucose. After single protease and trichloroacetic acid (TCA) treatments, the mannose content was significantly reduced to 3.96%, and glucose increased from 23.45% to 45.10%. Dual enzymatic hydrolysis also decreased the mannose and glucose contents to approximately 18%–35% and 7%–19%, respectively. The results suggest that enzymatic degradation could effectively remove the protein from DOMP accompanied by certain polysaccharides, especially mannose. The molecular weight, surface morphology, viscosity and particle sizes were measured. Enzymatic hydrolysis reduced molecular weight, decreased the viscosity, and increased the particle sizes, which indicates that the characterisations of DOMP samples were altered as structures changed. This study was a basic investigation into characterisation of DOMP to contribute to the processing of food by-products.

A chemo-enzymatic pathway was developed to transform 4-O-methylglucuronic acid (MeGlcpA) containing xylo-oligosaccharides from beechwood into clickable monomers capable of polymerizing at room temperature and in aqueous conditions to form unique polytriazoles. While the gluco-oligosaccharide oxidase (GOOX) from Sarocladium strictum was used to oxidize C6-propargylated oligosaccharides, the acid-amine coupling reagents EDAC and DMT-MM were employed and compared for their ability to append click functionalities to carboxylic acid groups of enzyme-treated oligosaccharides. While DMT-MM was a superior coupling reagent for this application, a triazine side product was observed during C-1 amidation. Resulting bifunctional xylo-oligosaccharide monomers were polymerized using a Cu(I) catalyst, forming a soft gel which was characterized by H¹NMR, confirming the triazole product.