Purification and characterization of a thermophilic 1,3-1,4-β-glucanase from Bacillus methylotrophicus S2 isolated from booklice.

An extracellular 1,3-1,4-β-glucanase-producing strain S2 was isolated from booklice and identified as Bacillus methylotrophicus. Furthermore, a homogeneous extracellular 1,3-1,4-β-glucanase GCS2 was purified by ammonium sulfate precipitation and cation-exchange chromatography. The gene for the 1,3-1,4-β-glucanase was cloned, and the nucleotide sequence was determined. Characterization of the purified enzyme revealed the molecular mass of 26 kDa and the optimum activity at pH 7.5, 55°C. The purified enzyme can highly hydrolyze carboxymethylcellulose including oat gum, barley β-glucan, CMC and lichenan, while low activity on avicel, cellobiose, filter paper, p-nitrophenyl β-d-cellobioside, and p-nitrophenyl β-d-glucoside, but no activity against microcrystalline cellulose or salicin. The enzyme was stable at wide range of pHs 5-10 and still maintained above 60% activity at 70°C. The enzyme activity was stimulated by Trixon X-100. The property of the enzyme GCS2 makes this enzyme a broad prospect in brewing and commercial detergent industry. To our knowledge, this is the first report of a 1,3-1,4-β-glucanase from microbes associated with booklice.