Recovery and separation of surfactin from pretreated Bacillus subtilis broth by reverse micellar extraction

The recovery and purification of surfactin from the fermentation broth of Bacillus subtilis ATCC (American Type Culture Collection) 21332 by extraction and stripping (back extraction) using reverse micelles was studied. Prior to extraction, the broth was precipitated by acid (HCl) at pH 4 and the precipitate was then dissolved in alkaline (NaOH) solution at pH 11. The effects of the type and concentration of surfactant, phase volume ratio, initial aqueous pH, and the presence of co-solvents on the extraction as well as the effects of the type and concentration of added inorganic salt and ethanol on the stripping were studied. It was shown that, in the absence of co-solvents, the extraction efficiency of 3.0 g/L surfactin from the pretreated broth by reverse micelles of 40 mM tri-n-octylamine (TOA) and 5 mM Aliquat 336 in n-hexane was more than 92%. The concentrations of the added inorganic salt (ammonium sulfate and sodium chloride) in the strip solution were also optimized. The purity of recovered surfactin from the TOA reverse micelles was higher than 90% when the strip solution contained 0.43 M of sodium chloride in water.

► The use of 40 mM TOA reverse micelles can extract 98% of 2.9 g/L surfactin at pH 6.5.
► Purity of surfactin recovered from TOA micelles by ethanol–NaCl solution reaches 91%.
► The use of 5 mM Aliquat 336 micelles can extracts 92% of 3.0 g/L surfactin at pH 9.0.
► Stripping of surfactin from Aliquat 336 micelles is hindered due to complex formation.
► TOA reverse micelles are recommended as the separating media for this purpose.