Purification Of Soybean Isoflavones By Membrane Method And Its Bacteriostatic

Soybean isoflavone is a kind of polyphenol compounds in soybean,which has antibacterial and antioxidant activities and has important application value in medical care and other fields..At present,the common purification methods of soybean isoflavones,such as macroporous resin adsorption and organic solvent extraction,would produce a lot of wastewater and organic solvent,and have high energy consumption.Membrane separation method has many advantages,and it has the advantages of low energy consumption and low pollution when used in the purification process of natural products.The membrane separation process can separate substances with specific molecular weight range,but the molecular weight distribution of impurities in soybean isoflavone extract is wide,so it is difficult to achieve a better purification effect by a single membrane separation process.Multiple membrane processes can be combined to separate impurities with different molecular weight step by step to achieve the purification of soybean isoflavone,but also avoid the problem of high energy consumption and high pollution in the traditional purification methods.In this project,soybean isoflavone extract was prepared from soybean meal,and better extraction results were obtained by optimizing the technological parameters.The influence of the technological conditions of ultrafiltration-nanofiltration process on mass transfer,separation effect and long-term stable operation of the filtration process was investigated systematically.The technological conditions of the filtration process were optimized and the purification effect was determined..Finally,the antibacterial effect of purified soybean isoflavones was determined.The extraction conditions of soybean isoflavone were optimized by single factor experiment,and the concentration of soybean isoflavone in the prepared extract was 0.351g/L.The process conditions of ultrafiltration were optimized.The membrane molecular weight cut off was 5000 Da,the temperature of extract was 35 ℃,the transmembrane pressure was 0.2 MPa,and the membrane surface flow rate was 12 cm/s,which provided guarantee for the stable operation of nanofiltration process.The process conditions of nanofiltration were optimized.The membrane molecular weight cut off was 1000 Da,the transmembrane pressure was 0.5 MPa,the temperature of exract was 35 ℃,and the membrane surface flow rate was 12 cm/s.Finally,the purity of soybean isoflavones can reach20.5% by ultrafiltration and nanofiltration membrane.The purified soy isoflavones can inhibit both Escherichia coli and Bacillus subtilis.After heat treatment,soybean isoflavone has antibacterial stability,but it has no inhibitory effect on two kinds of bacteria in strong acid and strong base environment.