Purification and characterisation of alkaline cellulase produced by a novel isolate, Bacillus sphaericus JS1

A novel strain of Bacillus sphaericus JS1 producing thermostable alkaline carboxymethyl cellulase (CMCase; endo-1,4-beta-glucanase, E.C. 3.2.1.4) was isolated from soil using Horikoshi medium at pH 9.5. CMCase was purified 192-fold by (NH4)(2)SO4 precipitation, ion exchange and gel filtration chromatography, with an overall recovery of 23%. The CMCase is a multimeric protein with a molecular weight estimated by native-PAGE of 183 kDa. Using SDS-PAGE a single band is found at 42 kDa. This suggests presence of four homogeneous polypeptides, which would differentiate this enzyme from other known alkaline cellulases. The activity of the enzyme was significantly inhibited by bivalent cations (Fe3+ and Hg2+, 1.0 mM each) and activated by Co2+, K+ and Na+. The purified enzyme revealed the products of carboxymethyl cellulose (CMC) hydrolysis to be CM glucose, cellobiose and cellotriose. Thermostability, pH stability, good hydrolytic capability, and stability in the presence of detergents, surfactants, chelators and commercial proteases make this enzyme potentially useful in laundry detergents.