Production and optimization of xylooligosaccharides from beech wood xylan by Bacillus amyloliquifaciens NRRL B-14393 xylanase and its antioxidant potential

Abstract

Background and objective Xylanase is a prominent industrially applicable enzyme. The present study investigated the applicability of crude Bacillus amyloliquifaciens NRRL B-14393 xylanase for production of xylooligosaccharides (XOS) from beech wood xylan (BWX). Materials and methods Crude xylanase activity was characterized in terms of xylanolytic activities present, pH, and temperature. The effect of incubation time, enzyme dosage, and substrate concentration on XOS production was investigated by response surface methodology based on central composite design. The antioxidant potential of produced XOS was assayed by 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and H2O2 methods besides their correlated total phenolic content was estimated using Folin-Ciocalteu colorimetric method. Results and conclusion The crude enzyme extract was β-xylosidase free and proved active over a broad pH range. The enzyme was thermostable up to 70°C and maximal enzyme activity was observed at 50°C and pH 8. Functional groups and purity of BWX were identified by fourier transform infrared spectroscopy (FT-IR). XOS yield was optimized to 16.02 mg XOS/ml xylan (400.45 mg XOS/g xylan) applying 1.70 mg enzyme/g xylan, 4.91 h incubation time and 1.08%, w/v substrate concentration. Xylobiose and xylopentose were identified by high performance liquid chromatography (HPLC) as the hydrolysate main end products. Total phenolic content of 115±0.60 mg GAEq/g XOS explicated the high antioxidant capacities exhibited by produced XOS.