Primary Study On Production Of Cod Skin Peptides By Probiotic Microbes Fermentation

College peptides are products of polypeptide. It can be extracted by enzymatic hydrolysis and microorganism fermentation from collagen which is the raw material. Compared with the college, college peptides hold more physical and chemical properties and physiological activities.Skins of cods with abundant college are good material to produce college peptides.For producing cod college peptides and removing fishy smell, 104 strains of microorganisms with protease and lipase activity and acid production ability were isolated from Natto, distiller's yeast, koji of vinegar and the guts of marine fishes. To identify the selected microorganism strains, classical identification was conducted through morphological, physiological and biochemical methods as the guide of"Yeasts: Characteristics and Identification"3rd edition,"Fungus Identification Handbook"and"Illustrated Genera of Imperfect Fungi, four edition","Berger's Mannal of Determinative Baceriology"eight edition. At the same time, 16SrDNA sequence was determined to confirm the classification position of bacteria by using molecular biology technology.According to identification resulst, 7 strains of probiotic microbes with protease and lipase activity and acid production ability were selected for cod skins fermentation. The 7 strains of probiotic microbes were identified to Bacillus subtilis, Bacillus cereus, Aspergillus niger, Rhodotorula aurantiaca and Saccharomyces cerevisiae. The optium fermentation medium and culture conditions were determined through Erlenmeyer flask liquid fermentation by the test of uni-factor and uniform design, respectively. The main procedure parameter were: fermentation temperature 30℃, the ratio of cod skin to water in medium 1:0.5, inoculation quantity 8%, bacteria: mould: yeast: acid production bacteria 3:1:1:2. The hydrolysis degree of the cod skins could reach 38.5%. The fermentation liquor was smelled better, and the flavor was smooh,soft and full on the palate.The crude polypeptides were precipitated by ethanol from fermentation liquor. Gel chromatography of molecular weight distribution was obtained by HPLC. The results indicated that the crude polypeptides had molecular weight, less than 4000Da..