ABSTRACT: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 60°C. 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 watersoluble 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 11°C higher value. This sustained the supposition that HPAN increases the thermostability of GOD.

ABSTRACT:Two new ultrafiltration membranes were obtained from a polymer mixture, containing 60% polyacrylonitrile (PAN) and 40% copolymer of methylmethacrylatedichlorophenylmaleimide (MMA-DCPMI). Membrane 1 (MB1) contains 40% DCPMI of the copolymer, and membrane 2 (MB2) contains 15% of the copolymer. The pore size, the specific surface, the water content, the water flux, and the selectivity were determined for the two membranes. The presence of dichlorophenylmaleimide in the copolymer ensures the preparation of membranes suitable for direct covalent enzyme immobilization without further modifications. These membranes were used for immobilization of glucose oxidase (GOD). High amount of bound protein was found on each of the membranes. High relative activities of the immobilized GOD were achieved, 72% for MB1 and 68% for MB2. The properties of the immobilized enzyme (GOD) were determined: optimum pH and temperature and pH, thermal, and storage stability, and then compared with the properties of the native enzyme. The kinetic parameters of the enzyme reaction, Michaelis constant (K m ) and maximum reaction rate (V max ), were also investigated. The results obtained showed that the ultrafiltration membranes prepared from the mixture of PAN and the copolymer MMA-DCPMI were suitable for use as carriers for the immobilization of GOD.