Corncob-induced endo-1,4-β-D-xylanase of Aspergillus oryzae MTCC 5154:: Production and characterization of xylobiose from glucuronoxylan

Eight different fungi were cultivated in a peptone-yeast extract medium containing 1% oat spell xylan (OSX) to evaluate endo-1,4-beta-xylanase secretion for xylooligosaccharide (XOS) production. Aspergillus oryzae MTCC 5154, Aspergillus flavus, Aspergillus niger, and Aspergillus ochraceus showed significant titers of endoxylanases, which were further used for the production of XOS from birch wood xylan (BWX). A. oryzae produced 89.5 +/- 1.13% XOS in the hydrolysate at 24 h of reaction. The effect of OSX, BWX, and raw corncob on the induction of endoxylanase in A. oryzae was studied, and the xylanase activity was maximum at 96 h of cultivation in 3% corncob containing medium. XOS produced at 36 h of reaction was 5.87 +/- 10.53 mg/mL (12 +/- 2% xylose, 48 +/- 12.43% xylobiose, and 40 +/- 3.6% higher oligomers) from 1% BWX. HPLC/refractive index detection and ESI/MS analysis of fractions obtained by GPC corresponded to neutral and 4-O-methyl-alpha-D-glucuronic acid substituted acidic oligosaccharides. The major fraction, beta-D-xylopyranosyl-(1 -> 4)-D-xylanopyranose was characterized using C-13 NMR.