The thermal stability of glucose oxidase (GOD) in solutions containing water-soluble hydrolyzed polyacrylonitrile (HPAN) and polyoxyethylene (POE) was studied as a function of time and temperature between 28 and 60degreesC. The results were compared with the thermal stability of GOD in solutions without polymers. The polymers studied were found to increase the enzyme thermal stability. The influence of the concentration of the water-soluble polymers on enzyme thermal stability was also studied. The best protection effect on enzyme thermal stability had 3 wt % solution of HPAN and 1 wt % solution of polyoxyethylene. Solutions with higher concentrations led to a quick deactivation of the enzyme. It was proved that the effect of 3 wt % HPAN solution was stronger than the effect of 1 wt % POE (59.0 versus 52.0%). The thermal transition of the enzyme was studied in both the presence and the absence of HPAN by DSC. The melting temperature of GOD in the presence of HPAN was shifted to an 11degreesC higher value. This sustained the supposition that HPAN increases the thermostability of GOD. (C) 2003 Wiley Periodicals, Inc.