Study On The Efficacy Of Ultrasonic Treatment Assisted Foam Fractionation For Recovering Proteins And Inhibiting Aggregation Induced By Gas-liquid Interface

Foam fractionation is an interfacial adsorption separation technology with the advantages of no pollution,mild operating conditions and easy amplification,and it has drawn the increasing attention of researchers.Recently,the industrialization of foam fractionation has been developed rapidly with the going deep of the research work on technology and mechanism.However,during foam fractionation,large gas-liquid interface area are usually induced the protein aggregation,resulting in the loss of protein functionality.This obstacle has severely limited the industrial application of foam fractionation in the yield of protein separation.So far,there are no any references on the ultrasonic treatment assisted foam fractionation for overcoming above obstacle.In order to further investigate the effect of ultrasonic wave on the protein properties and aggregation inhibition,this work was proposed to explore the influence mechanism of foam fractionation on protein activity using bovine serum albumin(BSA)as the medium system.The separation efficiency of ultrasonic treatment assisted foam fractionation and the functional properties of the foam were evaluated.Then,the effect of ultrasonic wave on protein aggregation behavior was studied.Finally,the interfacial adsorption and foam drainage in foam fractionation were optimized by changing the functional properties of glycoprotein system BSAed on ultrasonic effect.Firstly,a new method of ultrasonic treatment assisted foam fractionation was developed to effectively enrich bovine serum albumin(BSA)from its aqueous solution.Fourier transform infrared spectroscopy(FTIR)showed that the aggregation of BSA molecules on the gas-liquid interface during foam fractionation would be induced by the generation of intermolecular disulfide bonds.The results of high performance size exclusion chromatography indicated that the aggregation of BSA molecules was effectively inhibited by ultrasonic wave.Under the suitable conditions,the enrichment ratio and recovery percentage of BSA were 6.3 and 85.3%,respectively.Furthermore,the surface hydrophobicity,foam properties and emulsification of BSA solution were significantly improved by ultrasonic treatment through inhibiting the production of BSA aggregation during foam fractionation.These results provided a theoretical BSAis for the following research.Secondly,the technology of ultrasonic treatment assisted foam fractionation had also been used to recover casein from its aqueous solution.Experimental results indicated that ultrasonic wave can significantly inhibit the aggregation of casein molecules through decreasing particle size and strengthening interfacial adsorption.At an ultrasonic power of 600 W,the excess surface of casein in foam fractionation with ultrasonic treatment was increased by 46% compared to that foam fractionaton without ultrasonic treatment.Under the suitable operation,the enrichment ratio and recovery percentage of casein were 7.3and 90.2%,respectively.SEM and AFM analysis showed that ultrasonic treatment could not only inhibit the self-aggregation of casein molecules in aqueous solution,but also weaken the aggregation induced by the interfacial adsorption during foam fractionation.Subunits composition analysis revealed that ultrasonic treatment in foam fractionation had no effect on the structural integrity of casein molecules,but it could change the loose degree of the molecular structure.Finally,the electrostatic interaction between soybean protein isolate(SPI)and Gum Arabic(GA)by ultrasonic wave was studied.The optimum ratio of soybean protein isolate to gum arabic was 1:3,which was selected by emulsification.And their interaction mechanism could be clearly understood through the analysis of the physical and chemical properties of the electrostatic complexes before and after the ultrasonic.The results indicated that ultrasonic wave could increase the absolute value of Zeta potential and the surface hydrophobicity of the complex,but significantly reduce the turbidity.This suggested that cavitation caused the changes in the biomolecule structure,enhancing the electrostatic interaction between soybean protein isolate and gum arabic,and making the complex more emulsifying.The treated electrostatic complexes were used as the feeding solution of ultrasonic treatment assisted foam fractionation.Under the optimum conditions,the maximum enrichment ratio and recovery percentage of the electrostatic complexes reached.In this work,the technology of ultrasonic assisted foam fractionation has been developed to overcome the bioactivity loss and low recovery percentage,which were caused from protein aggregation induced by gas-liquid interface.Meanwhile,interfacial adsorption was strengthened by reducing the occurrence of aggregation.This is significant to provide some new ideas for treating the wastewater discharged from the files of food manufacture.