Hydrolysis of wheat flour arabinoxylan, acid-debranched wheat flour arabinoxylan and arabino-xylo-oligosaccharides by β-xylanase, α-l-arabinofuranosidase and β-xylosidase

Abstract

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 A2,3XX, 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.