Immobilized enzymes are the most sought preparations on the world market. They are used in medicine, veterinary food industry, winemaking and brewing. The simplest method for immobilizing biocatalysts on insoluble carriers is the adsorption. Its advantage is to preserve the natural conformation of the enzyme, which slightly reduces its catalytic ability compared to the native form. Ficin (EC 3.4.22.3), papain (EC 3.4.22.2), bromelain (EC 3.4.22.4) (Sigma) were chosen as objects of study, azocasein (Sigma) was used as a substrate for hydrolysis, and an acid-soluble high molecular weight chitosan (350 kDa, Bioprogress CJSC) was used as an immobilization carrier. Suitable buffer systems for immobilization were identified by the optimal ratio of protein content (mg per g of carrier), total activity (in units per ml of solution) and specific activity (in units per mg of protein). Ficin is immobilized on a chitosan matrix using glycine buffer with pH of 8.6. Glycine buffer with pH of 8.6-10.5 is optimal medium for adsorption of papain on chitosan. Bromelain is immobilized on a chitosan matrix under Tris-glycine buffer with pH 8.5 conditions.

This work was financially supported in the form of a grant from the President of the Russian Federation for state support to young Russian scientists - doctors of sciences (MD-1982.2020.4. Agreement 075-15-2020-325).