Purification and partial characterization of chitinase from a novel strain Aeromonas sp. PTCC 1691

A locally isolated and chitinase-producing Aeromonas bacteria strain PTCC 1691 was cultured and induced by powdered chitin for the production of chitinases. A chitinase enzyme was purified through ammonium sulfate precipitation, ion exchange chromatography and gel filtration (Sephadex G-50). Molecular weight of the purified chitinase (Chi-53) was estimated about 53 kDa through SDS-PAGE technique. The physicochemical properties of the chitinase was also determined and revealed that this enzyme was an acidic protein with a pI of 5.3. The optimal temperature for the chitinase activity was 55°C. Stability studies have indicated that this enzyme is stable over a pH range from 6 to 8, and the maximum activity was at pH 6.5. Among the metal ions, Cu^2+ and Co^2+ stimulated the enzymatic activity from 22 to 34%, whereas Hg^2+, Mg^2+, Br^3+ and Ag^+ inhibited the enzyme from 40 to 65%. The apparent Km and Vmax for colloidal chitin determined at 55°C and pH7 were 0.64 mg/mL and 2.3 μmol/μg/h, respectively.