Abstract
BackgroundThe application of chemical dispersants as a response to marine oil spills is raising concerns related to their potential toxicity also towards microbes involved in oil biodegradation. Hence, oil spills occurring under marine environments necessitate the application of biodispersants that are highly active, stable and effective under marine environment context. Biosurfactants from marine bacteria could be good candidates for the development of biodispersant formulations effective in marine environment. This study aimed at establishing a collection of marine bacteria able to produce surface-active compounds and evaluating the activity and stability of the produced compounds under conditions mimicking those found under marine environment context.ResultsA total of 43 different isolates were obtained from harbor sediments. Twenty-six of them produced mainly bioemulsifiers when glucose was used as carbon source and 16 were biosurfactant/bioemulsifiers producers after growth in the presence of soybean oil. Sequencing of 16S rRNA gene classified most isolates into the genus Marinobacter. The produced emulsions were shown to be stable up to 30 months monitoring period, in the presence of 300 g/l NaCl, at 4 °C and after high temperature treatment (120 °C for 20 min). The partially purified compounds obtained after growth on soybean oil-based media exhibited low toxicity towards V. fischeri and high capability to disperse crude oil on synthetic marine water.ConclusionsTo the best of our knowledge, stability characterization of bioemulsifiers/biosurfactants from the non-pathogenic marine bacterium Marinobacter has not been previously reported. The produced compounds were shown to have potential for different applications including the environmental sector. Indeed, their high stability in the presence of high salt concentration and low temperature, conditions characterizing the marine environment, the capability to disperse crude oil and the low ecotoxicity makes them interesting for the development of biodispersants to be used in combatting marine oil spills.
Highlights
Biosurfactants (BS) are amphipathic compounds produced by a variety of microorganisms
Bacterial isolation was performed by spreading serial dilutions of grinded sediment samples in sterile saline solution (30 g/l NaCl in distilled water) on agar plates of modified mineral salt medium containing 1%w/v of glucose as the major carbon source
Bacterial isolation and selection of biosurfactant/ bioemulsifier‐producers After bacterial growth in modified mineral salt medium (mMSM) broth with glucose, 43 pure isolates selected based on their different colony morphology after several successive streakings on mMSM agar medium, were screened for the BS/BE production
Summary
Biosurfactants (BS) are amphipathic compounds produced by a variety of microorganisms. These compounds could be of low-molecular weight type, which are generally glycolipids and lipopeptides, and high-molecular weight type which are mainly lipopolysaccharides, lipoproteins or a combination of both. In 2006, 250 patents have been deposited worldwide and were mainly related to the use of BE/BS in petroleum (33%) or cosmetic (15%) industries; in medicine (12%) and in bioremediation (11%) [3]. Oil spills occurring under marine environments necessitate the application of biodispersants that are highly active, stable and effective under marine environment context. Biosurfactants from marine bacteria could be good candidates for the development of biodispersant formulations effective in marine environment. This study aimed at establishing a collection of marine bacteria able to produce surface-active compounds and evaluating the activity and stability of the produced compounds under conditions mimicking those found under marine environment context
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