Stabilization of various α-chymotrypsin forms in aqueous-organic media by additives

The effect of different polyols (glucose, sorbitol or polyethylene glycol) on the stability of soluble and different covalently immobilized α-chymotrypsin forms in aqueous-organic solvent (ethanol, dioxane or acetonitrile) systems were investigated. Generally, immobilization resulted in remarkable improvement of the stability of the enzyme in aqueous-organic media: while immobilized forms retained 80–85, 70–90 or 30–60% of their initial activity in 50% (v/v) ethanol, dioxane or acetonitrile, respectively, the soluble enzyme showed only about 13, 35 or 2% remaining activity in the above aqueous-organic mixtures, respectively (after 60 min preincubation). Further improvement was found in the stability by the addition of polyhydroxy compounds. This effect depended on the feature of the support and the organic solvent. The most explicit increase in the stability was observed when the enzyme was immobilized on a silica-based support (Silochrome activated with p-benzoquinone) in aqueous-acetonitrile mixtures, where the activity of α-chymotrypsin was enhanced about 1.5–2 times by the addition of sorbitol or glucose as compared with its control.