Purification and Characterization of Novel Halo-Acid-Alkali-Thermo-stable Xylanase from Gracilibacillus sp. TSCPVG

An aerobic xylanolytic moderately halophilic and alkali-tolerant bacterium, Gracilibacillus sp. TSCPVG, produces multiple xylanases of unusual halo-acid-alkali-thermo-stable nature. The purification of a major xylanase from TSCPVG culture supernatant was achieved by hydrophobic and gel permeation chromatographic methods followed by electroelution from preparatory PAGE. The molecular mass of the purified xylanase was 42 kDa, as analyzed by SDS-PAGE, with a pI value of 6.1. It exhibited maximal activity in 3.5 % NaCl and retained over 75 % of its activity across the broad salinity range of 0–30 % NaCl, indicating a high halo-tolerance. It showed maximal activity at pH 7.5 and had retained 63 % of its activity at pH 5.0 and 73 % at pH 10.5, signifying the tolerance to broad acid to alkaline conditions. With birchwood xylan as a substrate, K _m and specific activity values were 21 mg/ml and 1,667 U/mg, respectively. It is an endoxylanase that degrades xylan to xylose and xylobiose and had no activity on p-nitrophenyl-β-d-xylopyranoside, p-nitrophenyl-β-d-glucopyranoside, p-nitrophenyl acetate, carboxymethylcellulose, and filter paper. Since it showed remarkable stability over different salinities, broad pH, and temperature ranges, it is promising for application in many industries.