Extraction of soluble arabinoxylan from enzymatically pretreated wheat bran and production of short xylo-oligosaccharides and arabinoxylo-oligosaccharides from arabinoxylan by glycoside hydrolase family 10 and 11 endoxylanases

The enzymatic, ecofriendly pretreatment of wheat bran with α-amylase from Bacillus amyloliquifaciens or B. licheniformis at 90 °C for 1.5 h followed by Neutrase at 50 °C for 4 h, aqueous liquefaction at 121 °C for 15 h and ethanol precipitation enabled the production of soluble arabinoxylan (AX) with purity of 70.9% and 68.4% (w/w) respectively. Process alternatives tried, to simplify the process and curtail the cost resulted in AX products with different purities, yields and arabinose to xylose ratio (A/X). Among the two glycoside hydrolase (GH) family endoxylanases evaluated, GH10 family hydrolysed soluble AX more efficiently with xylanase from Geobacillus stearothermophilus T-6 (GsXyn10A) producing maximum amount of quantifiable short xylo-oligosaccharides (XOS) and arabinoxylo-oligosaccharides (AXOS) (53% w/w) followed by the catalytic module of Rhodothermus marinus Xyn10A (RmXyn10A-CM) with 37% (w/w) conversion. The GH11 family endoxylanases, from Thermomyces lanuginosus (Pentopan Mono BG™) and Neocallimastix patriciarum (NpXyn11A) gave conversions of 21% and 22% (w/w) of the soluble AX, respectively (major AXOS products were not quantified). In addition to the XOS formed such as X2, X3 and X4, the AXOS products identified were A3X and A2XX in the case of GsXyn10A and RmXyn10A-CM while Pentopan Mono BG and NpXyn11A produced XA3XX as the major AXOS product