Value addition to corncob: production and characterization of xylooligosaccharides from alkali pretreated lignin-saccharide complex using Aspergillus oryzae MTCC 5154

Comparison of various pretreatments such as mild alkali/acid treatments and pressure cooking of corncob to expose its lignin-saccharide complex has been carried out to enhance enzymatic hydrolysis of xylan to xylooligosaccharides (XOS). Scanning electron micrographs of lignin-saccharide complex of native and pretreated corncob powder showed that the complex was greatly altered during alkali pretreatment. Hydrolysis of alkali pretreated corncob powder using a commercial endoxylanase produced 81+/-1.5% of XOS in the hydrolyzate equivalent to 5.8+/-0.14 mg ml(-1) of XOS. Reaction parameters for the production of XOS from corncob using endoxylanase from Aspergillus oryzae MTCC 5154 were optimized and an XOS yield of 10.2+/-0.14 mg ml(-1) corresponding to 81+/-3.9% with 73.5% xylobiose was obtained. HPLC/RID and ESI/MS analysis of XOS mixture and purified fractions showed that XOS was a mixture of neutral oligosaccharides of DP, 2-7.