中文摘要：

对前期获得的Thermus thermophilus海藻糖合酶进行了分子改造以提升其催化制备海藻糖的性能。利用定点突变技术,将第251位Pro突变为Leu,得到突变体P251L,并于E.coli BL21（DE3）中重组表达,重组菌在摇瓶中发酵酶活为6.9 U/m L。以突变体催化制备海藻糖的研究表明,当以0.3 g/m L麦芽糖为底物,初始反应p H为7.5,温度为50℃,加酶量为20 U/g麦芽糖时,转化率达到最高值62.0%,比天然酶高出13.0%。

英文摘要：

Trehalose synthase involves the direct conversion of maltose into trehalose by intramolecular transglucosylation. Trehalose has biological functions,and has been widely used in various fields. In the present study,the Thermus thermophilus trehalose synthase was molecular modified to improve itscapacity of the trehalose preparation. The Phe251 was mutated to Leu,resulting in the mutant of P251 L. The mutant was expressed in E. coli BL21（ DE3）,andthe enzymatic activity was 6. 9 U / m L when the engineered cells was cultivated for 28 h in shake flasks. The factors of trehalose preparation by the mutant was studied,under the optimum conditions of p H 7. 5,enzyme dosage of 20 U / g maltose,temperature of 50 ℃,the yield of trehalosereached 62. 0%,which was 13. 0% higher than that of the wild-type enzyme.