Purification and properties of a SDS-resistant xylanase from halophilic Streptomonospora sp YIM 90494

An extracellular xylanase from halophilic Streptomonospora sp. YIM 90494 was purified to homogeneity from a fermentation broth by ammonium sulphate precipitation, gel filtration chromatography and ion exchange chromatography. The purified xylanase appeared as a single protein band on SDS-PAGE with a molecular mass of approximately 50 kDa. The xylanase had maximum activity at pH 7.5 and 55 A degrees C. The enzyme was stable over a broad pH range (pH 4.0-10.0) and showed good thermal stability when being incubated at 60 A degrees C for 2 h. Kinetic experiments indicated that the enzyme had K (m) and V (max) values of 19.24 mg/mL and 6.1 mu mol/min/mg, respectively, using birch wood xylan as substrate. The inhibitory effects of various metal ions and chemical agents on the xylanase activity were investigated. It is greatly interesting to note that Ag+ ion and SDS, which strongly inhibited most xylanases reported previously increases the xylanase activity in this study. These characteristics suggest that the enzyme with new properties has considerable potential in industrial applications.