Characterization of Enzyme Released Antioxidant Phenolic Acids and Xylooligosaccharides from Different Graminaceae or Poaceae Members

Abstract

Xylooligosacchrides (XOS) and phenolic acids were simultaneously produced from hemicelluloses using crude enzyme mixture synthesized by a novel Bacillus subtilis KCX006. The strain synthesized XOS-forming endo-xylanase and de-branching α-L-arabinofuranosidase and esterase but not β-xylosidase. This enzyme mixture can improve the yield of XOS and phenolic acids from xylan due to the absence of hydrolysis of XOS by β-xylosidase and release of phenolic acids by esterase. Hence, the enzyme mixture was tested for simultaneous production of XOS and phenolic acids from xylan (28–35%)-rich Graminaceae or Poaceae plant biomass, such as wheat bran, sugarcane bagasse, bamboo, and rise husk. Hemicellulose fractions of the biomasses were extracted by alkaline treatment and hydrolyzed using crude xylanase mixture. The profiles of XOS and phenolic acids formed were analyzed by HPLC. The lyophilized hydrolytic products were further analysed by 1H NMR to identify the substitutions in XOS. The observed profile of XOS and phenolic acids varied with the biomass sources. Maximum amounts of XOS (665.2 mg/g dwt) and phenolic acids (89.69 μg/g dwt) were produced from hemicellulose A fractions of sugarcane bagasse and bamboo bagasse, respectively. HPLC and 1H NMR analysis of XOS revealed the formation of free- and arabino-XOS. Phenolic acids consisted of hydroxycinnamic and hydroxybenzoic acids and the antioxidant activity correlated well with hydroxycinnamic acids content. The crude enzyme of B. subtilis is useful to produce mixture of XOS and phenolic acids from biomass.