A process for production of trehalose by recombinant trehalose synthase and its purification.

The process for production of trehalose using trehalose synthase (TreS) to convert maltose into trehalose in one step is highly desirable in the industry. Nonetheless, the studies on industrial-scale production of trehalose by recombinant TreS in Escherichia coli are still scarce. In this study, a TreS from Pseudomonas putida ATCC47054 was expressed in E. coli BL21(DE3) via plasmids pET15b and pET22b. pET15b-treS showed better plasmid stability and TreS expression, which revealed that the highest activity, 39866±1420U/(g dry cell weight) at the final lactose concentration of 4g/L for 7h at 27°C in a 5-L fermentor at pH 8.0. The use of 30% (w/v) high-maltose syrup as a substrate can extend the temperature tolerance of TreS to 60°C. More than 64% of maltose can be converted into trehalose by adding 200U of TreS per gram of maltose at 50°C for 24h. The total sugar content of the trehalose syrup reached 95.0%±1.0% (w/w) after separation. The recovery rate of trehalose dehydrate reached 57.0%±2.0% after slow cooling, and the purity was 99.0±0.2%. Our study revealed a safe and reliable process of trehalose production by recombinant TreS.