Properties of a novel thermostable glucose isomerase mined from Thermus oshimai and its application to preparation of high fructose corn syrup.

Glucose isomerase (GI) is used in vitro to convert d-glucose to d-fructose, which is capable of commercial producing high fructose corn syrup (HFCS). To manufacture HFCS at elevated temperature and reduce the cost of enriching syrups, novel refractory GIs from Thermoanaerobacterium xylanolyticum (TxGI), Thermus oshimai (ToGI), Geobacillus thermocatenulatus (GtGI) and Thermoanaerobacter siderophilus (TsGI) were screened via genome mining approach. The enzymatic characteristics research showed that ToGI had higher catalytic efficiency and superior thermostability toward d-glucose among the screened GIs. Its optimum temperature reached 95°C and could retain more than 80% of initial activity in the presence of 20mM Mn2+ at 85°C for 48h. The Km and kcat/Km values for ToGI were 81.46mM and 21.77min-1mM-1, respectively. Furthermore, the maximum conversion yield of 400g/L d-glucose to d-fructose at 85°C was 52.16%. Considering its excellent high thermostability and ameliorable application performance, ToGI might be promising for realization of future industrial production of HFCS at elevated temperature.