Abstract:The fish's testis, commonly known as fish white, is often discarded as waste owing to its specific odor and is one of the by-products of fish processing. A basic protein, protamine, can be extracted from the testis of fish. Protamine has the advantages of high safety, good antibacterial performance, and high thermal stability. It can be used as an antibacterial ingredient in some foods in the field of food preservation. It has obvious antibacterial activity under alkaline conditions and is a promising antibacterial agent. Here, the testis of Takifugu obscurus was used as the raw material, and the protamine was extracted by acid extraction. The extraction coefficient was used to determine the optimal extraction parameters. According to the results of orthogonal test, the importance factors of the extraction of protamine are as follows: extraction times > sulfuric acid dosage > sulfuric acid concentration>95% ethanol; optimal extraction conditions are: sulfuric acid concentration 0.2 mol/L, sulfuric acid dosage is 2.5 times, the number of extractions was 2, and the amount of 95% ethanol was 2.5 times. Under this condition, the extraction rate of protamine from T. obscurus was 3.82%, and the protein content was 89.01%. According to the tricine-SDS-PAGE, the extracted crude protamine has two bands with molecular weights of 25 kDa and 20 kDa, respectively. Analysis of its lytic acid composition found that arginine and alanine content were relatively higher, accounting for 31.40% and 17.39%, respectively. This study is of great significance for the efficient use of testes of puffer-fish (dark-spotted oriental carp), and also lays a theoretical foundation for the application of stag beetle (dark-spotted oriental carp) protamine in the food and pharmaceutical fields.
