Glucose isomerization to fructose by immobilized glucose isomerase as an example of solid-liquid enzyme reaction has been studied in a down flow jet loop reactor (DJR). Conversion of glucose to fructose has been measured and compared with that formed in a batch reactor. The performance capability of the DJR was observed to be higher than that of the conventional reactors. The optimum operating conditions of the reaction system have been also determined using the Taguchi experimental design method. The effects of enzyme loading, draft tube diameter, position of nozzle inside the draft tube, and gas and liquid flow rates on glucose conversion have been considered. Analysis of the results revealed that the draft tube diameter has the highest and the ratio of liquid circulation rate to the gas flow rate has the least effects on the conversion of glucose. It was found that the experimental data could be correlated favoarably with a modified structure of the Michalis-Menten model consisting of two transition complexes. (c) 2004 Elsevier Ltd. All rights reserved.