Thermostable and alkaline tolerant xylanase production by Bacillus subtilis isolated form marine environment

The aim of the present study was to isolate a thermostable and alkaline tolerant xylanase producing strain from an estuarine environment, and to produce, purify and characterize the enzyme. The bacterium, Bacillus subtilis isolated from the estuarine environment was grown in shake flasks to derive the optimum culture conditions and also cultured in lab scale fermentor to obtain more xylanase. Maximum enzyme production (128 U/mL) was recorded in stationary phase (36 h) of the culture. The enzyme was purified using ammonium sulphate precipitation (60% saturation), followed by DEAE-cellulose column chromatography. The enzyme was optimally active at 55 degrees C and pH 9.0. Influence of metal ions on enzyme activity revealed that, Fe2+, Ca2+, and Mg2+, greatly enhanced the enzyme activity to 238, 148, 208 U/mL, respectively: whereas Hg2+ (0 U/mL) and EDTA (18 U/mL) strongly inhibited the enzyme activity. Based on the results obtained, xylanase isolated in this study may be useful in pulp pre-bleaching process to remove the hemicelluloses. The use of thermostable alkaline tolerant xylanase for enzyme assisted pulp bleaching could greatly reduce the need for pH and temperature readjustment, thus offering enormous technical and economic advantages.