Induction of Biosurfactant Production from a Native Isolated Moderately Halophilic Bacterium, Halomonas sp. MM93 in the Presence of Olive Oil and Study of its Stability

Biosurfactants are valuable microbial metabolites that have considerable applications in different industries. They offer so many advantages over their synthetic counterparts such as biodegradability, low toxicity, activity at extreme conditions, ability to be produced from renewable wastes and by-products. In the present study, biosurfactant production of Halomonas sp. MM93 in nutrient broth medium at 30°C after 72h was investigated using oil spreading and hemolysis tests. The emulsification capacity of the biosurfactant was also evaluated in a defined production medium during 96h. Effect of olive oil, n-Hexan, and kerosene as hydrophobic carbon sources to induction of biosurfactant production by the strain MM93 was also investigated. Due to the importance of stability in the case of industrial use, the effect of extreme temperature, pH and salinity on the stability of bacterial culture supernatant was evaluated. This strain created a clear zone of 2.5cm diameter in an oil-spreading test and its E24 index was 45%. Halomonas sp. MM93 could reduce the surface tension of the culture medium from 70 to 40 mN/m. Also, the produced biosurfactant showed remarkable stability at high temperature (100°C), extreme acidic and alkaline conditions (pH=2-12), and high salinity (20g/L). According to obtained data, native isolated moderately halophilic bacterium, Halomonas sp. MM93 could be considered as a potent strain in terms of producing stable biosurfactants for various industries especially the processes of increasing microbial recovery of oil that need Compounds with High surface activity and high stability.