Uniform poly(isopropylacrylamide) gel beads for immobilization of α-chymotrypsin

In this study, α‐chymotrypsin was immobilized via physical entrapment within large, uniformly spherical, and thermally reversible poly(N‐isopropylacrylamide) [poly(NIPAM)] beads. The gel beads were prepared in an aqueous dispersion medium by using Ca‐alginate gel as the polymerization mold. In this preparation, potassium persulfate/tetramethylethylenediamine and sodium‐alginate/calcium chloride were used as the redox initiator and the stabilizer systems, respectively. Thermoresponsive poly(NIPAM) gel beads 3 mm in size and including α‐chymotrypsin were produced by the proposed procedure. The use of an aqueous bead‐forming medium did not cause significant enzyme leakage during the preparation of enzyme‐gel beads. Michaelis–Menten kinetics was used to define the behaviors of enzyme‐gel beads prepared with different enzyme loadings. The Lineweaver–Burk plot indicated that the enzyme‐gel system had a reasonably higher Km value relative to that of free enzyme due to the internal mass transfer resistance against the substrate diffusion. The enzyme‐gel system exhibited the maximum activity at 30°C due to the thermoresponsive character of the carrier matrix. However, the maximum activity with the free enzyme was observed at 40°C. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1127–1139, 1998