Characterization of a Crude Thermostable β-galactosidase by the Bacterium PD1 Isolated from the Pong Dueat Hot Spring

Abstract

β-Galactosidase is an enzyme that hydrolyses lactose to glucose and galactose. The present study focused on the characterization of β-galactosidase from a thermophilic microoganism isolated from the Pong Dueat hot spring, Chaingmai Province, Thailand. o-Nitrophenyl-L-D-galactopyranoside (oNPG) was used as a substrate to determine the β-galactosidase activity from a strain PD1, which was found to be the active strain producing the highest â-galactosidase activity. The optimum pH and temperature for enzyme activity were 6.5 and 55°C, respectively. The enzyme was stable at pH range of 6 to 10. The half-life of enzyme at 80, 70, 60, 55, 50 and 45°C were 0.5, 2, 31, 62, 87 and 435 h, respectively. The K_m and V_max values for the synthetic substrate oNPG were 11 mM and 1.1×10^-2 mmolL^-1min^-1, respectively.