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 n-glucose to n-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 (GtGl) 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 n-glucose among the screened GIs. Its optimum temperature reached 95 degrees C and could retain more than 80% of initial activity in the presence of 20 mM Mn2+ at 85 degrees C for 48 h. The K-m and k(cat)/K-m values for ToGI were 81.46 mM and 21.77 min(-1) mM(-1), respectively. Furthermore, the maximum conversion yield of 400 g/L D-glucose to D-fructose at 85 degrees 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.(C) 2017 Elsevier Inc. All rights reserved.