Performance of a biosurfactant produced by a Bacillus subtilis strain isolated from crude oil samples as compared to commercial chemical surfactants

Abstract

In this work, the biosurfactant produced by a Bacillus subtilis strain isolated from crude oil samples was characterized and its properties compared with commercially available chemical surfactants. The purified biosurfactant production yield (Y(P/X)) was 0.20 g/gcell dry weight. The surface tension (29.0 mN/m) and critical micelle concentration (40 mg/l) were found to be similar to the values previously reported for surfactin. Temperature and pH stability of the biosurfactant were also evaluated. The biosurfactant was exposed to different temperatures (20, 37 and 46°C) during two weeks and was found to be as stable as the commercial chemical surfactants Glucopone(®)215, Glucopone(®)650, Findet(®)1214N/23 and linear alkylbenzene sulfonates (LAS). Moreover, the biosurfactant subjected to 121°C for 20 min did not exhibit a significant loss of surface activity. Contrary to the commercial chemical surfactants that were found to be stable over a wide range of pH (3.0-10.0), the biosurfactant was unstable precipitating at pH values below 5.0. The emulsification indexes showed that the biosurfactant possesses equal or superior capacity to form emulsions with n-hexadecane as compared to the commercial chemical surfactants. Moreover, the anti-adhesive activity of the biosurfactant and commercial chemical surfactants was evaluated. The biosurfactant showed some activity against Staphylococcus aureus and Escherichia coli. Nevertheless, no particular trend or special effect could be assigned to the use of commercial chemical surfactants as anti-adhesives. Results gathered in this work suggest that the biosurfactant recovered from B. subtilis EG1 constitutes an interesting alternative to the commercial chemical surfactants with potential use in several industries.