Abstract: Several operating parameters concerning both the stability of LEM and the high efficiency of separation,such as agitation speed,enviromental temperature,pH in tlie external phase,treating ratio,volume ratio of membrane phase to internal phase and initial concentra-tion,were studied.The selectivity at the presence of several impurities such as sodium chloride,glucose,metal ions or other amino acids was also investigated.Extraction of fermentation broth was perfoimed and the results were discussed.