Abstract
This study investigated the role of natural oil-degrading bacteria in the weathered biodiesel (BD), diesel (D) and light crude oil (L) in oil biodegradation in seawater with and without sophorolipid biosurfactant. Mixtures of artificial seawater and weathered oil with and without sophorolipid dispersant were incubated at 22 ± 1°C and 100 rpm for 28 days. Analysis of the remaining of total petroleum hydrocarbons showed degradation of 43 ± 0.7%, 45 ± 5.7% and 39 ± 4.6% of biodiesel, diesel and light crude oil, respectively, during the natural biodegradation and 44 ± 5%, 47.5 ± 3.9% and 44 ± 1% of biodiesel, diesel and light crude oil, respectively, with sophorolipid by the existing bacteria after 28 days. Characterization of bacteria isolated from the BD, D and L oil by 16S rRNA pyrosequencing showed that the Firmicutes was the dominant phylum in biodiesel (100%) and diesel (53%). The Actinobacteria was dominant in the diesel (47%) and the Proteobacteria (97%) and Actinobacteria (3%) were the two dominant phyla in the light crude oil. The hydrophobicity results showed that the bacteria consumed the hydrocarbons mainly by changing their cell surface structures in the natural biodegradation treatment and increase in the micellar dispersion of hydrocarbons in the biodegradation treatment with the sophorolipid. This study confirmed the significant contribution of natural bacteria in the weathered diesel, biodiesel and light crude oil in the biodegradation and the positive effect of sophorolipid on the biodegradation.
Highlights
Oil spills are usually referred to as the petroleum based hydrocarbons that enter to the aquatic environments [1,2,3]
If they can naturally produce surfactant-like products, they can uptake the oil droplets or hydrocarbons that encapsulated within the micelles [3,9]
Several studies have assessed the role of oil-degrading bacteria isolated from seawater in the biodegradation of petroleum hydrocarbons [7,22,61]
Summary
Oil spills are usually referred to as the petroleum based hydrocarbons that enter to the aquatic environments [1,2,3]. Microorganisms may first uptake the HCs that are soluble in seawater and interact with the hydrophobic hydrocarbons if they can change their cell surface structures to hydrophobic or hydrophilic states, based on the available HCs [3,9]. If they can naturally produce surfactant-like products (known as “biosurfactants”, that are composed of two parts, a hydrophilic part and a hydrophobic part), they can uptake the oil droplets or hydrocarbons that encapsulated within the micelles (structures that form when the biosurfactant molecules interact with water and HCs) [3,9]. Due to the chemical (e.g., hydrophobic nature of hydrocarbons), microbial (e.g., inability of all oil-degrading microorganisms in biosurfactant production) and environmental limitations (e.g., low temperature), the biological or chemical agents (e.g., chemical dispersants, nutrients) were added to the oil-impacted environments [5,14] to accelerate the dispersion and the bioavailability of HCs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
