Microwave irradiation-assisted isomerization of glucose to fructose by immobilized glucose isomerase

The isomerization of glucose to fructose by immobilized glucose isomerase (IGI, produced from Streptomyces murinus and immobilized on silica) was conducted under two different conditions—microwave irradiation and conventional heating to compare their overall effects. It was found that compared with conventional heating, microwave irradiation significantly enhanced the activity of IGI and the effects of acceleration might be non-thermal microwave effect. Under the optimum conditions of microwave irradiation-assisted isomerization (magnesium ion concentration of 50mM, 0.1M pH 7.5 phosphate buffered saline (PBS) buffer, 70°C, microwave power of 480W, agitation speed of 150rpm, glucose concentration of 0.8M and 2% IGI based on the solution weight percentage), 45% yield of fructose could be achieved in 16h, while only 43% yield of fructose was obtained until 24h by using conventional heating. These results indicated that microwave irradiation might be a fast and efficient method for enzyme-catalyzed isomerization of glucose to fructose.