The biosurfactant was extracted from cell-free broth at
72-h grown cells by step-by-step purification of acid
precipitates using adsorption chromatography. Bacterial
cells were removed from surfactant-containing medium by
centrifugation (10 000 rpm for 20 min). The supernatant was
subjected to acid precipitation by adding 6 N HCl to achieve
a final pH of 2.0 and allowing the precipitate to form at 4 曟.
The precipitate was pelleted at 10 000 rpm for 20 min, re-
dissolved in distilled water, adjusted to pH 7.0, freeze-
dried, and weighed. The dried surfactant was extracted with
acetone and dried with the aid of a rotary evaporator under
vacuum[18].