Immobilization of active protein by cross-linking to inactive protein

A process for producing an immobilized active protein in the form of a self-supporting flexible sheet or film or a self-supporting open-cell foam or sponge consisting essentially of mixing

• (a) active protein and
• (b) inactive protein simultaneously with
• (c) glutaraldehyde
• in a solvent-containing reaction medium to form a reaction mixture and reacting with active and inactive proteins with said glutaraldehyde under cross-linking conditions until the active protein is cross-linked with the inactive protein through bridges provided by the glutaraldehyde to form said sheet, film, foam or sponge, said active protein comprising up to 20 percent by weight of total active and inactive proteinic substance and said glutaraldehyde being in the range of from 0.5 to 8 percent by weight, based on the weight of total reaction mixture, said sheet or film being formed by spreading said reaction mixture on a surface before cross-linking and said foam or sponge being formed by freezing and slowly thawing said reaction mixture during said cross-linking.