Some characteristics and isolation of novel thermostable β-galactosidase from Thermus oshimai DSM 12092

The β-galactosidases belong to the class of hydrolytic enzymes and have been used as lactose hyrolysis. The enzyme is used in reducing lactose milk production, an outstanding industrial product used by a large lactoseintolerant population. This is the first detailed report of some characteristics of β-galactosidase and the gene encoding β-galactosidase in Thermus oshimai DSM 12092. The growth rate (μ, 1/h), and the doubling time (t D , h) for T. oshimai grown both in shaking flasks and in a bioreactor were determined. The optimal temperature and pH for β-galactosidase were determined as 75°C and 7.4, respectively. This enzyme was thermostable and was retained by more than 70% at 90°C for 3 h. The β-galactosidase from T. oshimai DSM 12092 was more stable in basic pH and Zn 2+ was the most effective divalent cation. Also, 2 steps of purification consisting of ammonium sulfate precipitation and gel filtration were employed and purified 32-fold.