Isolation and functional characterization of a biosurfactant produced by a new and promising strain of Oleomonas sagaranensis AT18.

Biosurfactant-producing bacteria were isolated from mangrove sediment in southern Thailand. Isolates were screened for biosurfactant production by using the surface tension test. The highest reduction of surface tension was achieved with a bacterial strain which was identified by 16S rRNA gene sequencing as Oleomonas sagaranensis AT18. It has also been investigated using different carbon and nitrogen sources. It showed that the strain was able to grow and reduce the surface tension of the culture supernatant to 25 mN/m. In all 5.30 g of biosurfactant yield was obtained after 54 h of cultivation by using molasses and NaNO₃ as carbon and nitrogen sources, respectively. The biosurfactant recovery by chloroform:methanol extraction showed a small critical micelle concentration value (8 mg/l), thermal and pH stability with respect to surface tension reduction. It also showed emulsification activity and a high level of salt concentration. The biosurfactant obtained was confirmed as a glycolipid by using a biochemical test, FT-IR and mass spectra. The crude biosurfactant showed a broad spectrum of antimicrobial activity and also had the ability to emulsify oil and enhance PAHs solubility.