Thermodynamic and kinetic characteristics of an a-amylase from Bacillus licheniformis SKB4

An amylolytic bacterial strain, Bacillus licheniformis SKB4 produced maximum amylase at pH 6.5 at 42 °C, and at late stationary phase (24 h) of growth. Starch and peptone were found the best supporting carbon and nitrogen source with C:N ratio of 1:2 for amylase production. The purified enzyme was non-responsive to most of the metal ions except K + and Mg ++ (1.0 mM). The enzyme was stable and active at pH 6.5. The enzyme showed optimum temperature at 90 °C with 10 min of half life (t ½ ) at 100 °C. The Q 10 of the enzyme was 1.0. The thermodynamic principles like activation energy, free energy for substrate binding and transition state of the enzyme were found 31.53, 5.53 and -17.4 KJ/Mol of starch, respectively. The kinetic constant like Vmax, Km, Kcat and catalytic efficiency (K cat/Km) for starch were found to be 1.04 µmol mg -1 min -1 , 6.2 mg ml -1 , 2 × 10 3 S -1 and 3.22 × 10 2 ml mg -1 S -1 , respectively. All these findings suggested that this amylase has unique characteristics for starch hydrolysis in respect to thermostability and kinetic properties.