Purification and characterization of an endo-1,4-β-glucanase from Bacillus cereus
A cellulase produced by Bacillus cereus (B. cereus), isolated from the local soil, was purified to homogeneity from culture broth. The enzyme had a molecular mass of 51.3 kDa. The optimal cellulase activity was at pH 8 and at the temperature of 55°C. The enzyme was stable at 50°C in the pH range of 5 to 9. The enzyme was stable up to 55°C above which stability decreased rapidly after incubation for 1 h. The enzyme showed the highest activity with carboxymethyl cellulose. Slight activity was also observed towards cellulose in the filter paper and xylan. For carboxymethyl cellulose, the cellulase had a Km of 2.12 mg/ml and Vmax of 5.37 μg/ml·min. The activity of the enzyme was not influenced by Fe2+, Zn2+, urea, EDTA, Ca2+, Co2+, K+ and Na+, but it was increased by 13% in the presence of Mn2+. Ba2+, C2O42-, Mg2+ and Cu2+ caused a loss in the enzyme activity. The FT-IR spectrum of this carboxymethyl cellulase (CMCase) showed the characteristic cellulase peaks. Infrared spectrum of the amide I and II bands of the CMCase showed that secondary structure of the CMCase mainly consists of α-helix structures in solid phase. This enzyme (the cellulase produced by B. cereus) is of high value in the industry applications (such as laundry) in the future.
Key words: Cellulase, Bacillus cereus, purification, characterization.