Ionic Liquid Aqueous Two-phase System Construction And The Extraction Of Proteins

Protein is a kind of complex organic compounds,is made up of amino acidmolecules which are formed by the linear array, the carboxyl and amino of adjacentamino acid residues are linked together by peptide bond. Protein is a kind ofbiological macromolecule material which vital to life, they play an important role inliving organisms catalysis, movement, structure, identification and regulation.Therefore, the study of extraction and separation of proteins has become a hotresearch. However, the traditional extractants are almost always organic solvents,which are volatile, highly toxic and environmentally hazardous. Therefore, it can beof great significance to find new safe and efficient extractants. In recent years, therehas been a new type of extraction and separation’s system, which is ionic liquid-basedaqueous two-phase system. They have been widely studied in extraction andseparation, and achieved good results.In this study, few ionic liquids and inorganic salt constitute the liquid-basedaqueous two-phase systems have been synthesized, and they are used to extractproteins (papain and bromelain). The results show that the ability to extract proteinsby various ionic liquids as follows:[Bmim]Cl>[Bmim]Br>[Bpy]Cl. The extractionrates of papain and bromelain in aqueous two-phase based [Bmim]Cl/K2HPO4canreach up to98.33%and97.35%respectively.The effect of the amount of ionicliquids (ILs), the concentration of K2HPO4, temperature, pH, and the volume ofprotein solutionwere discussed concretely.It is found that:(1) When raised the amount of ionic liquid, the extraction rates of papain andbromelain increase first then decrease in aqueous two-phase system based [Bmim]Cl/K2HPO4;but in aqueous two-phase system based [Bmim]Br, the extraction of papainand bromelainare on the rise; the extraction of papain rates is almost unchanged inaqueous two-phase system based [Bpy]Cl.(2) With the increase of the mass of phosphate, the extraction rates of papain andbromelain decrease in aqueous two-phase system based [Bmim]X(X=Cl,Br)/K2HPO4, and reduce trend of flat; but in aqueous two-phase system based [Bpy]Cl, theextraction rates of papain is decreased obviously.(3) With increase of the system temperature, the extraction rates of papain andbromelainslight increasein aqueous two-phase system based[Bmim]X(X=Cl,Br)/K2HPO4;but the rates of papain increase at the very beginningand then decrease in aqueous two-phase system based by[Bpy]Cl/K2HPO4.(4) With variation of the system pH, the extraction rates of papain and bromelainare the same trend in three kind of ionic liquids, when pH of the solution is near theproteins isoelectric point, target extraction effect is best.