Kinetic study comparison of immobilized glucose isomerase (gensweet and sweetzyme it) in stirred tank reactor and packed bed reactor

Pinaki Saha, Dibya Das, Madhumita Saha, Sudipta Saha, Pratyusa Sar, Debabrata Bera*

Jadavpur University, Kolkata, West Bengal, India

ABSTRACT

D- Glucose/xylose isomerase catalysis the reversible isomerization of aldoses to ketoses such as D-glucose and D-xylose to D-fructose and D-xylose respectively. High fructose corn syrup (HFCS), a low calorie sugar substitute for cane sugar, utilizes Glucose isomerase enzyme for conversion of glucose to fructose. The conversion of glucose to fructose favors more at high temperature, providing an incentive to utilize thermostable and thermoactive glucose isomerase in High fructose corn syrup (HFCS) production. Present studies emphasize on enzymatic conversion and optimization using Sweetzyme IT extra & Gensweet, commercially available glucose isomerases. The experiments were carried out for enzymatic conversion of glucose to fructose using Gensweet and Sweetzyme in Packed bed reactor (PBR) and Stirred tank reactor (STR). Maximum conversion was seen in Stirred tank reactor (STR) using both of these enzymes, approx 10 % more Fructose conversion comparing it to packed bed reactor (PBR). Also, Stirred tank reactor (STR) reaction conditions such as pH, buffers, cofactor (MgSO4) requirement were optimized to achieve optimum enzyme activity. Analysis of enzymatic conversion samples was done using HPLC-RID (using Zorbax Column). The importance of the divalent cation MgCl2 for optimal enzyme activity was investigated. The enzyme performed best at pH 7.5 and 60°C, using 10mM MgSO4 as a cofactor. Utilizing Gensweet in Stirred tank reactor (STR), the maximum fructose transformation was 44 %. The most activity was detected with Sodium phosphate buffers, and EPPS buffers at pH 7 and 8, accordingly, whereas the least activity was reported with TRIS HCl buffer.

Keywords:

High fructose corn syrup, Stirred tank reactor, packed bed reactor, Optimization, Sodium phosphate, EPPS buffers and TRIS HCl buffer