Erwinia rhapontici E602株β-半乳糖苷酶的分离纯化及性质研究

β-galactosidase producing bacterial strain E602 was isolated from frozen soil and identified to be Erwinia rhapontici. This strain was cultured at 26℃ with the induction of lactose for production of the β-galactosidase. This enzyme was then purified with ammonium sulfate fractionation, ion exchange and gel filtration chromatography for further studies of the enzymatic characteristics. The purified enzyme had a molecular weight of about 100 kDa. The optimum reaction temperature and pH of this enzyme was 40℃ and pH 7.0 respectively, indicating that this enzyme was a mesophilic neutral β-galactosidase. However, the enzyme retained about 15% activity at 10℃, which also suggested cold-adaptive property of this enzyme. Kinetics of this enzyme was studied and the Km and Vmax of this enzyme was 0.21 mmol/L and 263.16 μmol/mg min-1. Metal ions such as Li+, K+, Mg2+ and Zn2+ can activate the enzymatic activity obviously, while Cu2+ and Fe2+ inhibited the activity. The lactose hydrolysis in milk had been also investigated and results suggested that this enzyme may be suitable for milk processing.