Study On The Purification Of Cottonseed Peptide By Membrane Technology

Membrane separation technology as a high-tech,has developed rapidly in recently 20 years. Membrane separation become effective methods for separating and concentrating low concentration solution. Peptide could be separated from protein and cellulose by choosing suitable microfiltration membrane;peptide could be concentrated and separated from inorganic salts by choosing suitable nanofiltration membrane. In this paper microfiltration and nanofiltration was used to separate and purify peptide from cottonseed protein.The selection of microfiltration membrane, the effect of pressure and temperature were researched; using nanofiltration to concentrate peptide was discussed; the ability of each cleaning reagent and ways was determined then.The inorganic ceramic membrane of 100nm was determined as the purify membrane. The membrane flux was increased by operating pressure within a certain range, and that was the pressure control; when the operating pressure exceeds 0.5MPa, the separation process became the gel layer control.Temperature has effected greatly on membrane flux and the membrane flux increased with the increasing temperature. After microfiltration, the purity of cottonseed protein peptide increased from 86.3% to 91.3%. The objective rejection rates of specific sugar contents in low purity fructooligosaccharides and membrane flux,which depend on syrup concentration and transmembrane differential pressure,were calculated in fitting methods.The study on cottonseed protein by nanofiltration experiments showed that the salt rejection rate of 70% and peptides about 90% retention rate when the concentration factor of 8 times. With the increasing of concentration, the flux rapid attenuation.When the concentration ratio greater than 4, the trend of the concentration slowing. In the research system, the pressure, concentration ratio and temperature have significant impact on membrane flux. The best nanofiltration condition is the pressure for the 1.2 MPa, concentration factor of 8 times and 50℃. The result of membrane fouling factor analysis shows that the key factor is concentration factor.Tthe temperature has limited impact on membrane fouling, and the operating pressure on membrane fouling were not significantly affected. Using sodium dodecyl sulfate, sodium polyphosphate and EDTA compound cleaning agent for cleaning. Then the insoluble material removed by nitric acid of inorganic ceramic membrane,and inorganic salt deposition removed by citric acid of nanofiltration.These can return the pure water flux resume close to the prior, which can make the membrane to maintain stable and continuous work.