Antimicrobial and antioxidant activities of protein hydrolysate from terrestrial snail Cryptozona bistrialis

Previously, we have shown that seven different snail proteins for antimicrobial activity. Among them, a protein extract from terrestrial snail Cryptozona bistrialis inhibited the growth of pathogenic bacteria and fungi. In the present study, we hydrolyzed C. bistrialis protein extract to identify peptides exhibiting the antimicrobial and antioxidant activities. The tissues of the land snail C. bistrialis were homogenized and digested with three different enzymes: papain, trypsin, and pepsin. During enzyme hydrolysis, the degree of hydrolysis (DH) and percentage of peptide bond breakage was calculated. Among the protein hydrolysates by the three enzymes, the papain-digested hydrolysate of C. bistrialis showed the highest DH (27% ± 0.5%) at 37°C temperature, pH 6.0, and enzyme/substrate ratio of 4:100 for 6-hour incubation. Only the papain-digested protein hydrolysate showed antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus with the maximum zone of inhibition of about 27.3 ± 0.5 mm and 28 ± 0.5 mm, respectively. Based on these results, papain digestion was selected for further antioxidant study. The papain-digested protein hydrolysate showed maximum 2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity about 73%, 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid radical scavenging activity is 70%, and ferric reducing antioxidant power was increased when increasing the concentration of the protein hydrolysate of C. bistrialis. This hydrolysate is an alternative as natural antimicrobial and antioxidant compounds.