The invention discloses a method for extracting
polymyxin B from a
fermentation broth of the
polymyxin B. The method for extracting the
polymyxin B from the
fermentation broth of the
polymyxin B comprises the following steps: a, conducting
solid-liquid separation on the
fermentation broth of the
polymyxin B and obtaining a filtrate; b, extracting the filtrate with a polar
organic solvent, and extracting an extract liquor reversely with water when the extract liquor is at the potential
hydrogen (pH) value of 1.0-2.0; c, adding the reversal extract liquor which is obtained from the step b into inorganic salt, wherein the volume of the reversed extract liquor of the inorganic salt is 3-8% (w / v), and adjusting the pH value to be 9.0-10.0 so that the
polymyxin B is obtained after
precipitation and
sediment. Preferably, the method for extracting the polymyxin B from the
fermentation broth further comprises a step of d: reacting the polymyxin B and
sulfuric acid to form salt, and dissolving and precipitating, thereby obtaining the
polymyxin B sulfate. The polymyxin B or the
sulfate prepared by means of the method is higher in yield and purity, the purity of a product is above 85%, the tilter is above 8100IU / g, and the yield is above 60%. The method for extracting polymyxin B from the
fermentation broth has the advantages of being easy and convenient to operate, short in
time consuming, low in requirement of equipment, and capable of recycling the
organic solvent and being used for large-scale industrial production.