The Application Of Membrane Separation In The Collagen Extraction Process From The Shin Of Grass Carp

In this study, Polyvinylidene Fluoride(PVDF) microporous membrane and Polysulfone (PS)ultrafiltration membrane were used to purify the collagen of grass carp skin. PS ultrafiltration membranesof different Molecular Weight Cut Off (MWCO) were prepared to apply to the collagen seperation withdifferent molecular.According to the routine collagen purification process, acid/water pickling and water pickling wereproposed. In this part, the collagen concentration, operating pressure and the initial temperature of solutionwere discussed.First, compared the PVDF membrane and PS membrane in collagen purification process.The result showed that PVDF microporous membrane had a better effect. When the collagen concentrationwas1.2%, operating pressure was0.25MPa and the initial temperature was30℃, purified three times, thepH of collagen was4.15, chloride ion removal rate was69.34%,concentrating times was9.67. Then twocollagen purification processes were compared. It proved that water pickling was better. When collagenconcentration was1.2%, operating pressure was0.25MPa and the initial temperature was30℃, afterpurified, the pH of collagen was6.3, chloride ion removal rate was80.7%,concentrating times was7.2.PS ultrafiltration membrane was prepared by phase transformation technique and the PS as membranematerials, N,N-dimethyl acetamode (DMAc) as solvent, Polyethylene pyrrole(PVP) as additive.Experiments focused on the effects of concentration of PS, additive, evaporation time on membraneproperties.The preparation technics of different MWCO are followed:①MWCO=10000, PS:PVP:DMAc=22:3:75,the mixing temperature was65℃, the mixing timewas10h, defoaming temperature was45℃and the defoaming time was12h, evaporation time was120s,coagulation bath was20℃.②MWCO=2000, PS:PVP:DMAc=22:2:76,the mixing temperature was65℃, the mixing timewas10h, defoamingtemperature was45℃and the defoaming timewas12h, evaporation time was120s, coagulation bath was20℃.③MWCO=1000, PS:PVP:DMAc=22:3:75,the mixing time10h, defoaming temperature was45℃and the defoaming time was12h, evaporation time was160s, coagulation bath was20℃.They all had goodalkali resistance, acid resistance were different.The collagen was degradated by collagenase I. Degradation temperature, enzyme dosage and degradationtime were investigated in this study. By determining the hydrolysis degree of collagen protein(DH,the ratioof the peptide bonds eleavaged/total peptide bonds in protein), it could conclude that at35℃, with8mlenzyme solution, and degradated16h, DH=38.7%. PS membranes with different MWCO were used incollagen separation after enzymatic degradation, separated by MWCO=10000and2000, the collagenmolecular weight between2000and10000was96.5%, separated by MWCO=1000, the collagen molecularweight between1000and2000was74.4%, below1000was100%. The result showed that the interceptionof different molecular weight by the ultrafiltration membrane had a good classification effect.