Study On The Physicochemical Properties Of Collagen And Biological Activity Of Collagen Peptides From Giant Croaker (Nibea Japonica)

Owing to the boom in marine product processing industry,massive amounts of by-products are being generated,which are either discarded or simply used as animal feed or fertilizer.Hence,methods of using these by-products to produce high value-added items are urgently required.Bioactive peptides from marine resources possess many physiological functions,including antioxidative,anticancer,antibacterial,angiotensin-converting-enzyme?ACE?inhibitory,immunomodulatory,hepato-protective and wound healing activities.Therefore,extraction of bioactive peptides from marine wastes and by-products might offer new avenues for their utilization,consequently preventing environmental pollution and creating enormous economic benefits.In the present study,collagen was extracted from the skin of Nibea japonica,and its physicochemical and functional properties were determined,which laid a foundation for its application in cosmetics additives or biological materials.In addition,collagen peptide was prepared from the skin of Nibea japonica,and its physicochemical and functional properties were also determined,which laid a foundation for promoting wound healing.The main research results of this experiment are as follows:?1?The enzymatic hydrolysis conditions of PSC were optimized by single factor and response test.After regression fitting,the quadratic polynomial regression equations of enzymatic amount,feed-liquid ratio and enzymatic hydrolysis time were obtained as follows:extraction yield of collagen=83.73+3.53X₁+1.47X₂+1.78X₃-0.11X₁X₂-0.59X₁X₃-0.80X₂X₃-3.68X₁₂-2.03X₂₂-1.89X₃₂.After regression fitting and validation test,the optimum extraction parameters were determined as follows:the concentration of pepsin is 1389 U/g,the solid-liquid ratio is 1:57 and the hydrolysis time is 8.67 h.The extraction yield of collagen from Nibea japonica skin was 84.85%,which is well agreement with the predict value of 85.03%??2?The acid-soluble collagen?ASC?from Nibea japonica skin was extracted,and the physicochemical properties and functional properties of ASC and PSC were determined.The results showed that the extraction yield of ASC and PSC were 15.35%and 20.23%respectively?dry weight?;ASC and PSC were with the highest contents of Gly,followed by the Ala,Pro and Hyp,and the Gly content was 35.1%and 34.8%,respectively;the T_d of ASC and PSC were about 34.5?;The ASC and PSC were composed of two distinct?chains??₁ and?₂?,some?chains?dimer?,and small amounts of?chains?trimer?.The composition of the peptide chain is highly consistent with that of type I collagen,indicating that both ASC and PSC belong to type I collagen???1?2?2?.The infrared spectra of ASC and PSC are almost identical,with five amide bands being amide A,amide B,amide I,II and III.The contents of As,Pb and Hg in ASC and PSC are lower than those in national standards.Compared with glycerol,PSC has good moisture-absorption?Ra?and retention abilities?R_h?,non-toxicity and sensitization to NIH-3T3 cells.?3?Collagen Peptides?MCPs?was obtained by enzyme hydrolysis of Nibea japonica skin with four proteases;MCPs contained many polypeptides with molecular weights?10kDa and most amino acid residues were hydrophilic.MCPs promoted the proliferation of NIH-3T3 cells.In vitro scratch assays indicated that MCPs significantly affected the scratch closure rate and promoted the migration of NIH-3T3 cells.Moreover,to determine the signaling mechanism of MCPs,western blotting was used to determine the expression levels of NF-?B p65,IKK?,and IKK?of the NF-?B signaling pathway.Our results indicated that MCPs increased the protein levels of NF-?B p65,IKK?and IKK?in MCPs-treated NIH-3T3 cells.In addition,MCPs increased the protein levels of epidermal growth factor?EGF?,fibroblast growth factor?FGF?,vascular endothelial growth factor?VEGF?,and transforming growth factor?TGF-??in NIH-3T3 cells.