[25] Immobilization of enzymes and microbial cells in gelatin

Gelatin is an inexpensive, abundant, and safe material largely used as a food additive. The protein nature of gelatin, its high hydrophilicity, and, consequently, its strong swelling power provide environmental conditions very favorable for immobilized enzymes or whole cells and reduce the mass-transfer resistance to the diffusion of substrate and reaction product. Gelatin chain lengths and the well-balanced number of polar and nonpolar groups play a fundamental role in gel formation. For these reasons, gelatin has generally been disregarded as a possible matrix for entrapping enzymes and whole cells. However, thermostability and mechanical strength can be achieved by treating gelatin gels with formaldehyde, a hardening agent and has proved to be the most efficient among several other agents used in industry for making gelatin insoluble and impermeable.