Purification and characterization of β-galactosidase from Aspergillus fumigatus PCSIR-2013

Abstract

Extra cellular β-galactosidase enzyme was purified and characterized from Aspergillus fumigatus PCSIR2013. Estimated molecular mass of the enzyme was approximately 95 kDa. by native polyacrylamide gel electrophoresis. Initially, different fermentation parameters were optimized for maximum production of β-galactosidase. The kinetic study of the partially purified enzyme exhibited that it remained active in broad range of temperature from 25°C to 70°C with an optimum of 60°C. The Km and Vmax were calculated as 9.95mmol/l and 51.78 U/ml/min, respectively. The optimum pH was 5.0, when reaction mixture was incubated for 30 min. The enzyme was very stable in the presence of different metal ions, although Na+ (16%) stimulates the activity at 10mM concentration. In contrast, Ba+2 and Hg+2 have negative effect on enzyme activity and activity decreased to 54% and 19%, respectively. Thermo stability study was revealed that the enzyme retained 72% of its activity at 50°C. Whereas, when enzyme was incubated at 60°C for 120 min, its residual activity was decreased to 42.0%. However, the enzyme was completely inactivated at 80°C after 120 min of pre-incubation. Among different surfactant which incorporated with enzyme, Tween 20 and Triton X-100 both have stimulatory effect and activity increased to 29% and 17%, respectively.