Study on properties of thermostable a-galactosidase and hydrolysis of lactose in milk

It showed by properties determination of a-galactosidase from reco mbinant escherichia coli that, the optimum temperature and pH of the enzyme acti vity were 55 ℃and pH 7.0, respectively and exhibited thermostability at 50 ℃. The enzyme was significantly activated by some alkali and alkali-earth metal io ns such as K+,Mg2+and Mn2+, but inhibited by heavy metal ions such as Pb2+, Sn2+, Zn2+and Cu2+. It also showed through hydrolysis tests of lactose in mi lk that the a-galactosidase was exhibited strong ability to hydrolyze lactose in milk and reached above 55 percent of hydrolysis ratio by reacting with one un it per mililitre enzyme into milk holding under 55 centigrade for 2 hours.