## 3 Discussion
The following biodegradation tests were carried out in that study: in vitro hydrolytic degradation of collagen membranes in phosphate-buffered saline at 37 \({}^{\circ}\)C; enzyme resistance test: samples were immersed in 0.13% porcine trypsin solution and incubated at 37 \({}^{\circ}\)C; bacterial collagenase resistance test using collagenase solution from _Clostridium histopathologic_ bacteria. It is a mixture of several enzymes, including collagenase, that breaks down collagen tissue. This preparation contains collagenase, nonspecific proteases, and clostripain and exhibits neutral protease and aminopeptidase activity. The experiment demonstrated that collagenase exhibits the best values for the biodegradation of collagen membranes, as in our studies. The study [38] also investigated the effect of _Clostridium histopathologic_ collagenase on the degradation of collagen-containing wastes. The results show that when peptides are present on the surface of collagen fibrils, the amide bonds break at a much faster rate. The fibrillar structure of collagen leads to more pronounced destruction and dissolution of collagen peptides under the action of collagenase. The amount of peptide fractions with different molecular weights in enzymatic hydrolysis samples of collagen-containing wastes is significantly comparable (Tables 2 and 3). In both cases, hydrolysis was almost complete with collagen degradation to low-molecular-weight peptides. At the end of the enzymatic hydrolysis process, both collagenase and collagen hydrolyzate samples contained a significant amount of low-molecular-weight proteins with a small number of high-molecular-weight peptides. Obviously, collagenase showed significantly higher activity (Figures 1-3) than neutrale, but no significant difference in the qualitative characteristics of hydrolysis products was found (Tables 1 and 2). Similar results are described in [39; 40; 41; 42]. It is known that enzymatic hydrolysis of collagen of secondary collagen-containing raw materials by collagenase leads to the production of certain bivalent products, which then spontaneously react with the formation of more complex, stable cross-links [39]. This involves many different spontaneous, non-specific reactions that correlate with glucose and the products of its oxidation, which leads to the development of glycation end products [40]. Glucose, ribose, and other sugars and sugar oxidation products react with lysine, hydroxylysine, and arginine to form complex products, of which only a few have been characterized to this date [39; 42]. In addition to peptides and carbohydrates, a significant amount of glycoprotein and glycosaminoglycan is formed [39]. In humans and animals, glycosaminoglycans are covalently bound to the protein part of proteoglycans and are not found in free form. Enzymatic hydrolysis allows isolating glycosaminoglycans from secondary collagen-containing raw materials that are not covalently bound to proteoglycans [39]. Thus, during the enzymatic hydrolysis of collagen-containing raw materials by collagenase, the biological activity of the obtained low-molecular-weight compounds is significantly higher than the biological activity of low-molecular-weight compounds obtained as a result of the enzymatic hydrolysis by Neutrase 1.5 MG. The study [43] presents the results of studying protein hydrolyses obtained from shrimp waste, mainly consisting of heads and shells of _Peneusmonodon_, by enzymatic hydrolysis for 90 min using four microbial proteases (alkalase, neutrale, protamex, and flavurzyme), where the corresponding enzymes were compared to select the best protein profile for studying. The alkalase that showed the best result was used to optimize the hydrolysis conditions. The maximum hydrolysis degree under the action of alkalase was 33.13%. The obtained protein hydrolyzate contained a high content of protein (72.3%) and amino acids (529.93 mg/g), of which essential amino acids and aromatic amino acids were 54.67-55.93% and 38.32-39.27%, respectively.