Virgibacillus dokdonensis VITP14 produces α-amylase and protease with a broader operational range but with differential thermodynamic stability.

Abstract

Extracellular α-amylase and protease were coproduced from halo tolerant Virgibacillus dokdonensis VITP14 with banana peels (2% w/v) as substrate. The pH optima for α-amylase and protease were 6.5 and 7.0, respectively. The temperature optima of α-amylase and protease were 30 and 50 °C, respectively. Both the enzymes were active in the presence of various metal ions (1 mM of Ni2+ , Ca2+ , Ba2+ , Sr2+ , and Mg2+ ), detergents (Tween 20, Tween 80, Triton X-100), and other additives (2-mercaptoethanol and urea). Both the enzymes followed Michaelis-Menten type enzyme kinetics with Vmax of 121.40 and 4.17 μmol Min-1 mL-1 and Km of 0.59 and 0.28 mg mL-1 for amylase and protease, respectively. Amylase showed higher activation energy for inactivation (75.55 kJ mol-1 compared to 59.70 kJ mol-1 for protease) and higher thermal stability (reflected by longer half-life 53.23 Min compared to 0.11 Min for protease) at 60 °C. The coexistence of amylase and protease could be attributed to the difference in the optimum temperatures of activity and thermal stability of the two enzymes.