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.