Exploring the potential of halophilic bacteria from oil terminal environments for biosurfactant production and hydrocarbon degradation under high-salinity conditions

The wastewater from oil production can be exceptionally saline and contain a complex mixture of hydrocarbons, many of which are highly toxic. This study aimed to identify and characterize 141 halophilic bacteria isolated from production water and activated sludge from Marine Terminal Almirante Barroso (Brazil) and evaluate their potential for biosurfactant production and biodegradation of distinct petroleum hydrocarbons. Sequencing and phylogenetic analysis of the 16S rRNA gene revealed that the halophilic bacteria retrieved are distributed among 20 genera and four phyla (Proteobacteria, Firmicutes, Actinobacteria and Flavobacteria). RAPD fingerprinting was used to differentiate isolates at the infra-specific level, revealing 79 different genetic profiles. GC-MS analysis carried out with eight strains confirmed their ability to efficiently degrade alkanes and aromatic compounds under halophilic conditions, with preference for aromatic degradation. Eleven strains showed significant ability for reduction of the surface tension (from 72 to 40 mN/m) and for emulsification (up to 71%) of four different types of oils (mineral, soybean, diesel and kerosene). Results gathered in this study demonstrate a high taxonomic and genetic diversity of the halophilic bacterial strains isolated from the oil terminal samples and an outstanding potential for further use in biotechnological processes such as biosurfactant production or bioremediation.