Method for purifying sodium surfactin

The invention relates to the field of microbial fermentation and discloses a method for purifying sodium surfactin. The method comprises the following steps of: taking a surfactin fermentation liquid to centrifugally collect supernatant and collecting a trapped liquid after membrane filtration; and slowly adding an alkaline solution to carry out neutralization reaction, thus obtaining the finished product of sodium surfactin after drying the reaction liquid. The method has beneficial effects that the purity of the finished product of sodium surfactin prepared after purification reaches 75-80%; in order to further improve the purity of the finished product of sodium surfactin, such impurities mixed in surfactin as proteins are removed by centrifugation after membrane filtration and the purity reaches 80-85%; further, the pH value of the centrifugal supernatant is adjusted with acid, so that surfactin settles and the purity of the finished product reaches 85-88%; and the purity of the finished product of sodium surfactin prepared by the method can reach 75-88% and the finished product of sodium surfactin can be widely applied in the field of cosmetics as a cosmetic additive.