Production of novel halo-alkali-thermo-stable xylanase by a newly isolated moderately halophilic and alkali-tolerant Gracilibacillus sp. TSCPVG

An aerobic xylanolytic Gracilibacillus sp. TSCPVG growing at moderate to extreme salinity (1-30%) and neutral to alkaline pH (6.5-10.5) was isolated from the salt fields near Sambhar district of Rajasthan, India. β-xylanase (18.44. U/ml) and β-xylosidase (1.01. U/ml) were produced in 60. h in the GSL-2 mineral base medium with additions of (in g/l) Birchwood xylan (7.5), yeast extract (10.0), tryptone (8.0), proline (2.0), thiamine (2.0), Tween-40 (2.0) and NaCl (35) at pH 7.5, 30 °C and 180. rpm. The β-xylanase was active within a broad salinity range (0-30% NaCl), pH (5.0-10.5) and temperature (50-70 °C). It exhibited maximal activity with 3.5% NaCl, pH 7.5 at 60 °C. It was extremely halotolerant retaining more than 80% of activity at 0 and 30% NaCl and alkali-tolerant retaining 76% of activity at pH 10.5. The acetone precipitated xylanase was highly stable (100%) at variable salinities of 0-30% NaCl, pH of 5.0-10.5 and temperatures of 0-60 °C for 48. h. HPLC analysis showed xylose, arabinose and xylooligosaccharides as hydrolysis products of xylan. This is the first report on hemi-cellulose degrading halo-alkali-thermotolerant enzyme from a moderately halophilic Gram-positive Gracilibacillus species. © 2010 Elsevier Ltd.