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Extraction of Tryptophan enantiomers by aqueous two-phase systems of ethanol and (NH4)2SO4


Correspondence to: Fei-peng Jiao, School of Chemistry and Chemical Engineering, Central South Universty, Changsha 410083, China. E-mail:



As an important extraction technique, aqueous two-phase extraction is especially applicable to bioseparation. This work has focused on using a novel kind of aqueous two-phase system (ATPS), for the enantioseparation of tryptophan.


Only limited kinds of salts could form effective phases with ethanol. The salting-out abilities of various salts and the final characteristics of ATPS were investigated. The results show that increase in the amount of phase-forming components and decrease in pH from 6 to 2.5 are both beneficial for the enantioseparation of tryptophan; enantioselective extraction and partitioning behavior are mainly dependent on the pH of solution, the type of chiral extractant and its concentration. Furthermore, salt, ethanol and temperature also have some effects on the enantioseparation. Finally, the most reasonable extraction mechanism of the tryptophan enantiomers was suggested.


The novel ATPS composed of ethanol/ammonium sulfate proposed in this studyhas good ability for the extraction of tryptophan enantiomers. © 2012 Society of Chemical Industry