Purification and some properties of low-molecular-weight extreme halophilic xylanase from Chromohalobacter sp TPSV 101

Abstract

An extreme halophilic xylanase was purified from cultures of Chromohalobacter sp. TPSV 101 by ultrafiltration, hydroxylapatite and gel filtration chromatography. SDS-PAGE of the xylanase showed an apparent homogeneity and molecular weight of 15 kDa. The xylanase had maximum activity at pH 9.0 and 65 degrees C in the presence of 15-25% NaCl and was stable in the range of pH 7.0-9.0, temperature between 50 and 70 degrees C. The enzyme was stable at 50-65 degrees C for 1 h retaining 100% activity and by retaining 60% activity at 80 degrees C. The xylanase was completely inhibited by Hg2+ ions and was partially inhibited by Ca2+, Cu2+ and Pb2+ ions, whereas Zn2+, Mn2+ and Co2+ ions enhanced its activity. Both EGTA and EDTA enhanced its activity. It was active in solutions containing water-insoluble organic solvents and osmolytes. Kinetic experiments indicated that the enzyme had K-m and V-max values of 0.2 mg/ml and 1.17 mu mol/ml/min for oat spelt xylan. The major products of the oat spelt xylan hydrolysis were xylose and xylobiose: after prolonged incubation xylose was the major end product. (C) 2011 Elsevier B.V. All rights reserved.