Immobilisation of diverse biocatalysts, such as viable Bacillus subtilis cells secreting proteases, Mucor membrane-bound lipase, and yeast invertase, on carriers obtained from polyvinyl alcohol (PVA), results in stabilisation of enzymatic proteins. All these entrapped catalysts displayed high catalytic and mechanical stability.

B.subtilis cells entrapped in PVA-cryogels beads (by freezing-thawing method in a two phase system) are able to produce extracellular proteinases (metalloproteinase and subtilisin) for at least 5 years, because of high mechanical stability of the carrier and easiness regeneration of proteolytic activity after application for protein (e.g. casein) hydrolysis. The advantage of PVA-cryogels is their porosity enabling protein penetration into the beads.

Membrane-bound lipase from Mucor circinelloides (mycelium treated with acetone and dried) was immobilised with about 25% recovery of activity, both in PVA-crogels beads and in PVA-gels obtained by means of salting out the polymer with ammonium sulphate. The entrapment of the lipase in dried PVA beads enhances their thermostabitity and operational stability during repeated uses for p-nitrophenyl acetate hydrolysis. Alginate supplement to the PVA-gels changes some of their properties.

The yeast b-fructofuranosidase (Novo) was stabilised by encapsulation in PVA gel solidified with glutaraldehyde in presence of BSA or gelatine as stabilising agents. Highly stable biocatalyst in form of membranes, obtained in this way can be applied for continuous conversion of sucrose. It was observed that the entrapped invertase was active at wider pH range and at higher temperatures, in comparison to the soluble enzyme.

Studies on PVA-cryogel biocatalysts were executed using the computer image analysis system.