Abstract: Trehalase is a trehalose hydrolase,which can distinctively catalyze trehalose into two molecules of glucose. In order to have a recombinant expression and application of the trehalase gene Tre F from Escherichia coli str. K-12 substr. MG1655 in E. coliBL21（DE3）,the Tre F was amplified by PCR,and a recombinant strain E. coli BL21（DE3）/pET-24a（+）-Tre F was constructed. The highest activity reached 107 U/mL when the strain was cultured in shake flask for 24 h at induction temperature 25℃and IPTG induction concentration 0.4 mmol/L. Further study of the enzymatic properties indicated that the optimal pH and temperature was 7.0 and 50℃,respectively. The crude enzyme was used in the hydrolysis of trehalose. The reaction conditions for the conversion was as the following：initial trehalose concentration 300 g/L,initial pH 7.0,reaction temperature 30℃,enzyme concentration 84 U/g. When the reaction was performed under this specified condition,the glucose yield reached the maximum of 98.4 % at 36 h. This paper is the first report on the recombinant expression of trehalase gene Tre F of E. coli str. K-12 substr. MG1655 in E. coli BL21（DE3）.

Key words: trehalase, gene cloning, recombinant expression, enzyme properties