Preparation Of Peptides By Probiotic Fermentation From Cod Skin And Its Antioxidant Properties In Vitro

During the fish processing, a large amount of waste is generated. Fish skin is a major by-productof the fish-processing industry, causing wastage and pollution, and could provide a valuable sourceof collagen. The major advantage of marine collagen sources is that they are not associated with therisk of bovine spongiform encephalopathy (BSE) outbreaks. Fish collagen peptide, which molecularweight is less than10000dalton, is easy absorb by skin, and is good raw material for cosmetics,health food, skin care and anti-wrinkle etc. To produce cod skin collagen peptides,20strains ofmicroorganisdms with lipase and protease activity were isolated from Natto, vinegar koji andfertilizer. Using morphological, cell structure and physiological and biochemical methods, theselected microorganisdms were identified on the basis of “Berger’s Manna l of DeterminationBaceriology” eight edition,“Yeasts: Characteristics and Identification”3rd edition,“IllustratedGenera of Imperfect Fungi, four edition” and“Fungus Identification Handbook”. Meanwhile, thoughmolecular biology techniques, the16SrDNAsequence of the selected bacteria was determined.According to identification resulst,4strains of probiotic microbes with lipase and proteaseacttvity were selected for multistrains fermention.The4strains of probiotic microbes were identifiedto Bacillus subtilis, Aspergillus niger and Saccharomyces cerevisiae. By using the single factorexperiments and orthogonal tests, the optimal fermentation conditions were bacteria: mould: yeastproduction bacteria2:1:1, the ratio of cod skin to water in medium1:1.5, inoculation quantity8%,andfermentation temperature30℃. In this fermentation condition, the hydrolysis degree of the codskins could reach50.65%, the flavor of the fermentation liquor was smooh soft and full on thepalate without odor. Animal acute toxicological experiments showed that the fermention productswere non-toxic, indicating that he seleced four microbes were probiotics.Four collagen peptides fractions CSPI(5k~10kDa）、CSPⅡ(3k~5kDa)、CSPⅢ（1k~3kDa）、CSPⅣ（below1kDa）were obtained from fermentation liquor by ultrafitration. The DNA damageprotection ability, radical scavenging activity were evaluated using chemiluminescence (CL). Anatural antioxidant Vc was used as positive control. The results showed that cod skin peptides withdifferent molecular weight range had higher antioxidant activity than Vc. The antioxidant activities increased in the order of CSPI(5k~10kDa）<CSPⅡ(3k~5kDa)<CSPⅢ（1k~3kDa）<CSPⅣ（<1kDa,which correspond with the general rule that the smaller of the molecular weight of peptides, thestronger ofthe antioxidation activity.The volatile components of fermentation liquor were analyzed using the SPME-GC-MSmethods. The results showed that there were24kinds ofvolatile constituents before multistrainsfermentation, but there wasonly3kinds of volatile constituents after24h..