High Efficient Extraction of Tryptophan Using Deep Eutectic Solvent-based Aqueous Biphasic Systems

Abstract

Deep eutectic solvent-based aqueous biphasic systems were established as greener replacements of organic solvents for the extraction of amino acid in this work. Choline chloride/polyethylene glycol 2000-based deep eutectic solvent was synthesized and characterized by element analysis, thermogravimetric analysis, and Fourier-transform infrared spectroscopy. The phase diagrams of deep eutectic solvent+salt (Na3C6H5O7/Na2CO3/NaH2PO4/K2HPO4)+H2O aqueous biphasic systems were determined at 298 K and the aqueous biphasic systems were applied to extract the tryptophan for the first time. The extraction conditions of amino acid concentration, deep eutectic solvent amount, salt dosage, and the extraction temperature were investigated and optimized. Under the optimum conditions, the extraction efficiency of tryptophan can reach up to 86.72-93.88 % using deep eutectic solvent-based aqueous biphasic systems with the salt of Na2CO3, Na3C6H5O7, NaH2PO4 or K2HPO4. UV/Vis and fluorescence spectra confirmed that the conformation of tryptophan did not change after extraction. Deep eutectic solvent-based aqueous biphasic systems have great potential application in highly efficient extraction of biologically relevant amino acids and other substances.