Glutathione extraction and mass transfer in di-(2-ethylhexyl) ammonium phosphate/octanol reverse micelles

Di-(2-ethylhexyl) ammonium phosphate (DEHAP)/octanol reverse micellar extraction was demonstrated to be an effective method to separate glutathione (GSH) from yeast fermentation broth. The effect of several important factors including pH, DEHAP concentration, and types and concentration of cations was investigated, and the optimum operating conditions were obtained by orthogonal experiments, for forward extraction: pH 2.5, DEHAP concentration = 0.16 mol/L, W0 = 10, phase ratio (organic/aqueous, v/v) = 2:1, K+ concentration = 0.1 mol/L, and extraction time = 15 min. For back extraction: pH 10.5, Ca2+ concentration = 0.6 mol/L, phase ratio (aqueous/organic, v/v) = 3:1, back extraction time = 45 min. Under the optimum operating conditions, the yield of GSH can reach 65% after one forward and three back extractions. No protein and only a small portion of amino acids were detected in the lyophilized product of GSH. The study on the extraction kinetics showed that the volumetric mass transfer rates of the forward and back extraction are around 0.209 s−1 and 0.054 s−1, respectively, which is very close to the literature results of electrostatic force-based reverse micellar extraction of protein.