| Egg white contains three main active proteins,namely ovotransferrin(OVT),ovalbumin(OVA)and lysozyme(LYZ).They have high nutritional value and unique advantages in the immunological research,antibody development and antibacterial properties.There are still many problems for the existing methods in the separation of these active proteins from egg white,such as complex steps,high operation cost or protein’s denaturation.These all make it difficult to realize industrial amplification.Therefore,the demand for seeking an efficient,simple and clean separation technology for the active protein in the egg white is of great significance for the large-scale application of active protein as well as for the construction of healthy China.Electrodialysis with porous membrane(EDPM)is a new membrane separation technology that introduces one or more porous membranes into the traditional electrodialyzer,so as to realize the organical combination of electrodialysis and the separation process of filtration membrane.This technology realizes the highly selective separation of charged biological macromolecules not only by the size screening of porous membrane but also by the different migration direction and migration speed of charged macromolecules.It expands the application field of electrodialysis,meanwhile reduces the concentration polarization and membrane pollution that exists in the process of pressure-driven membrane separation.Considering the technical advantages of EDPM,this paper attempts to apply it in the direct separation and purification of three active proteins in egg white,hope to provide a new method for the separation and purification of active proteins in egg white.In this paper,according to the particle size of three proteins and their differences in charge and electrophoretic migration rate under different p H conditions,the separation of OVA and LYZ was firstly conducted.The effects of membrane material,operating voltage,the flow rate of feed and recovery liquid as well as the volume ratio of feed and recovery liquid on the separation performance were investigated.Results showed that when the PVDF100 membrane was used,the recovery rate of LYZ was higher and the unit energy consumption was lower,with 30.65% and 1.69 k W·h/g,respectively,and the purity of LYZ was high as 100%.Aadditionally,the interaction between filtration membrane and LYZ was weaker using filtration membrane with larger membrane pore size,which could promote the migration of LYZ.When the operating voltage was 5 V,the EDPM process was relatively stable,and the recovery rate of LYZ could reach 28.8%,with the specific energy consumption of 1.71 k W·h/g and purity of 100%.When the flow rates of feed and recovery solution were 35 ml/min and 50 ml/min,the recovery rate of LYZ protein was higher and the specific energy consumption was lower.The recovery rates of LYZ were 29.78% and 28.8%,respectively,and the specific energy consumption was1.71 k W·h/g and 1.64 k W·h/g,respectively.The purity of LYZ was still 100% for this two flow rates.When the volume ratio of feed liquid to recovery liquid was 1:1.5,the recovery rate of LYZ was high as 32.24%;The specific energy consumption was lowest,which was only 1.52 k W·h/g and the purity kept at 100%.The separation of OVT and OVA was performed by using their different electrophoretic mobility at a specific solution p H.The effects of membrane materials and cell configurations on the separation performance were investigated.Results showed that the PES50 membrane was conducive to the migration of OVA.At the end of the experiment,the recovery rate of OVA was 12.06%,the specific energy consumption was 1.23 k W·h/g,and the purity of OVA was 98.26%.The migration of OVA was affected by its interaction with the membrane more than the pore size of the membrane.When cell configuration of AACCⅡ was used,the migration rate of OVA was relatively stable,and recovery rate could reached 18.94% with the specific energy consumption of 0.51 k W·h/g,and the purity of 97.57%.It was indicated that the stable salt solution concentration of the feed solution and local electric field intensity of the feed chamber were both conducive to the migration of OVA.At the same time,the specific energy consumption can be significantly reduced.The recovery rate of OVA with cell configuration of AACCⅡ was 57.05%,higher than that with cell configuration of ACAC,and the specific energy consumption was 66.45%,lower than that with cell configuration of ACAC,but the purity of OVA was almostly not affected.Based on the above research,the PES50 and PVDF100 filtration membranes were both placed in the stack with cell configuration of AACCII to simultaneously separate OVT,OVA and LYZ.The effect of the p H of feed and recovery solution on the separation performance was investigated,and the membrane fouling of each filtration membrane as well as anion and cation exchange membranes stacked in R1 and R2 recovery chambers was characterized after the experiment.Results showed that the maximum recovery rate of 7.46% of OVA was achieved at p H 8.0 of the feed and recovery solution.Under this condition,the specific energy consumption was0.76 k W·h/g,and the purity was 98.78%.LYZ had the highest recovery rate of 51.03%with the specific energy consumption of 1.07 k W·h/g and purity of 100%,when the p H of the feed and recovery solution was 7.0.Aadditionally,the recovery rate of OVA and LYZ as well as the retention rate of OVT were lower at p H 6.0 of feed and recovery solution because that p H was close to the isoelectric point of OVT.The retention rates of OVT in the feed solution could reach 89.78%(p H 6.0),96.84%(p H7.0)and 95.23%(p H 8.0),respectively,at three different p H of the feed and recovery solution.The characterization results of membrane fouling showed that the degree of membrane fouling during EDPM process was not serious,and there was no filter cake layer on the membrane surface existing in the pressure driven process.The degree of membrane fouling of EDPM process was far less than that of the pressure driven process.This study shows that the simultaneous separation of three active proteins in egg white can be realized by using EDPM process via the different charge or electrophoretic migration rate of OVT,OVA and LYZ.High purity of OVT,OVA and LYZ can be obtained with enough operating time and stable experimental conditions.The low membrane fouling degree is conducive to the continuous operation,so as to reduce the separation cost and improve the separation efficiency of EDPM process.This research provides a novel technology with high selectivity,conveniet operation and easy industrial amplification for the separation and purification of active proteins in egg white,which would expand the application field of EDPM and enrich the basic theory of EDPM process. |
