Native bilge water bacteria as biosurfactant producers and implications in hydrocarbon-enriched wastewater treatment

Seawater and bilge water samples were used to isolate hydrocarbon-degrading bacteria to be screened for biosurfactant production in the presence of different carbon sources, namely tetradecane, D-glucose and sunflower oil. The panel of tested isolates, affiliated to Alcanivorax, Acinetobacter, Pseudomonas, Halomonas and Marinobacter genera, showed promising results both in terms of emulsifying activity and surface tension reduction. The selected strains Marinobacter sp. BIC3M3, Alcanivorax sp. BIC1A5 and Halomonas sp. BIC1H44 achieved total raw biosurfactant amount of 3.148, 2.922 and 2.596 g/L, respectively. The sunflower oil, here proposed as lowcost carbon source, was successfully used by all strains as substrate for biosurfactant production, with the only exception of Halomonas sp. BIC1H44, while different efficiency levels were detected during incubation in the presence of glucose and tetradecane. Among all strains, Marinobacter spp. strains from bilge waters were proven to be very competitive, although this genus has been poorly reported for biosurfactant production. The high efficiency exhibited by some strains (especially Alcanivorax sp. BIC1A5, Acinetobacter sp. BIC1AC, and Marinobacter sp. BIC3M3) during growth with tetradecane and sunflower oil suggested a promising potential for application in bioremediation purposes and hydrocarbon-enriched wastewater treatment.