Immobilization of catalase in poly(isopropylacrylamide-co-hydroxyethylmethacrylate) thermally reversible hydrogels

Catalase was entrapped in thermally reversible poly (isopropylacrylamide-co -hydroxyethyl-methacrylate) (pNIPAM/HEMA) copolymer hydrogels. The thermore sponsive hydrogels, in cylindIl-rical geometry, were prepared in an aqueous buffer by redox polymerization. It was observed that upon entrapment, the activity retention of catalase was decreased between 47 and 14%, and that i ncreasing the catalase loading of hydrogel adversely affected the activity. The kinetic behaviour of the entrapped enzyme was investigated in a batch reactor. The apparent kinetic constant of the entrapped enzyme was determin ed by the application of lMichaeiis-Menten model and indicated that the ove rall reaction rate was controlled by the substrate diffusion rate through t he hydrogel matrix. Due to the thermoresponsive character of the hydrogel m atrix, the maximum activity was achieved at 25 degrees C with the immobiliz ed enzyme. The K-m value for immobilized catalase (28.6mM) was higher than that of free enzyme (16.5mM). Optimum pH was the same for both free and imm obilized enzyme. Operational, thermal and storage stabilities of the enzyme were found to increase with immobilization. (C) 1999 Society of Chemical I ndustry.