An Unusual Reversible Sol−Gel Transition Phenomenon in Organogels and Its Application for Enzyme Immobilization in Gelatin Membranes

An unusual phenomenon is observed for gelatin solutions (1.7−6.8%) in the microemulsion system of 0.3 M bis(2‐ethylhexyl)sulfosuccinate sodium salt in isooctane and 14.5% distilled water. Highly viscous gels obtained at temperatures above 30 °C become free‐flowing liquids at low temperatures (5−10 °C). This reversible temperature‐dependent sol−gel transition phenomenon is used to immobilize several enzymes, such as lipase from Candida rugosa , alcohol dehydrogenase from baker's yeast, mandelonitrile lyase from Sorghum bicolor , and horseradish peroxidase in the gelatin matrix by solubilizing the enzyme in a microemulsion‐based gelatin solution at low temperature (<5 °C) and then cross‐linking with glutaraldehyde. The enzymes retain 70−80% of their activity after immobilization and can be used in biotransformations in organic solvents without any changes in enantioselectivity. This work provides a unique low‐temperature technique for enzyme immobilization in a biocompatible gelatin matrix with a great flexibility of size and shape.