Fermentations were carried out at the same growth conditions to follow the variation of the medium superficial tension, which indicated the production of biosurfactants. The results are shown in Table 3. B. megaterium C116 showed the fastest growth and the superficial tension of the medium was reduced more quickly in comparison to the other two isolates. Nevertheless, the reduction of superficial tension occurred similarly for the three Bacillus isolates, at the end of the growth phase. Biosurfactants produced during microorganism growth in liquid medium tended to concentrate on the foam, so less activity was observed in the liquid (Cooper et al., 1981). This could be the reason for the superficial tension be higher in this study than that found in the published literature, where it was lower than 30 mN/m (Kim et al. 1997). In order to isolate tensoactive compounds, HCl was used to precipitate peptides in the final sample of each culture, which was centrifuged, and the sediments dissolved in deionized water at pH 12. The supernatant, the water, and the water with dissolved precipitates had their superficial tension measured.