Partial purification and properties of cellulase-free alkaline xylanase produced by Rhizopus stolonifer in solid-state fermentation.

摘要

The properties of a cellulase-free alkaline xylanase produced by Rhizopus stolonifer through fermentation in a solid medium containing wheat bran were determined. The purified enzyme obtained after molecular exclusion chromatography had an optimum temperature between 40 and 60 degrees C. The optimum pH of xylan hydrolysis was determined at 45 degrees C. There were 2 pH optima (6.0 and 9.0), indicating the presence of isoforms. The Km and Vmax values at pH 6.0 (7.42 mg/ml and 0.47 micro mol/mg protein, respectively) were lower than those at pH 9.0 (10 mg/ml and 0.87 micro mol/mg protein, respectively). The xylan hydrolysis products at pH 6.0 and 9.0 were xylotriose and xylo-oligosaccharides. However, after 120 minutes, xylobiose was observed at pH 9.0. In addition, traces of xylose were observed. It is concluded that the enzyme is an endo-xylanase [endo-1,4-beta-xylanase]..