Production and in vitro evaluation of xylooligosaccharides generated from corncobs using immobilized Penicillium occitanis xylanase

Penicillium occitanis xylanase 3 expressed in Pichia pastoris, termed PoXyn3, was immobilized on chitosan with glutaraldehyde by covalent coupling reaction. The immobilization yield and the xylanase activity recovery were 98.8 +/- 2.5% and 94.45 +/- 3.5%, respectively. The optimum pH was not affected by immobilization, but the immobilized PoXyn3 exhibited more acidic and large optimum pH range (pH 2.0-4.0) than that of the free PoXyn2 (pH 3.0). The free PoXyn3 had an optimum temperature of 50 degrees C, whereas that of the immobilized enzyme was shifted to 65 degrees C. Immobilization increased both pH stability and thermostability when compared with the free enzyme. It also exhibited high storage stability and retained 70% of its initial activity after 120 days. The main hydrolysis products yielded from corncob extracted xylan were xylobiose and xylotriose. The resulting xylooligosaccharides (XOS) could be used as a special nutrient for lactic bacteria. Therefore, prebiotic effect of XOS was evaluated by in vitro fermentation using known probiotic strains viz. Bifidobacterium adolescentis and Lactobacillus acidophilus. The results of this study revealed better growth of Bifidobacterium spp on XOS as a carbon source than Lactobacillus spp. (C) 2014 Elsevier B.V. All rights reserved.