A chemical and histological study on the effect of (1→4)-β-endo-xylanase treatment on wheat bran

A purified thermostable (1 --> 4)-beta-endo-xylanase, solubilised 50% of the arabmoxylan in cell walls of wheat bran. The monosaccharide composition of the hydrolysis products suggest that the xylanase solubilised only arabinoxylans with a high xylose/arabinose ratio, i.e. low substitution. In addition to the release of oligosaccharides, the endoxylanase treatment solubilised some protein (3% of wheat bran dry matter). A microscopical study of the bran before and after endoxylanase treatment showed that the aleurone layer had been completely disorganised. Endoxylanase treatment released 80% and 50%, respectively, of the carbohydrate of the dissected aleurone layer and inner bran (composed of the nucellus, seed coat, tubes cells and cross cells) In contrast, the outer bran (composed of hypodermis and epidermis) was resistant to endoxylanase treatment. (C) 2002 Elsevier Science Ltd.