Abstract
Bioremediation is one of the promising environment-friendly approaches to eliminate oil contamination. However, heavy oil is known to degrade slowly due to its hydrophobicity. Therefore, microorganisms capable of producing biosurfactants are gaining substantial interest because of their potential to alter hydrocarbon properties and thereby speed up the degradation process. In this study, six bacterial consortia were obtained from the oil-spilled beach areas in Miyagi, Japan, and all of which exhibited high potential in degrading heavy oil measured by gas chromatography with flame ionization detector (GC-FID). The polymerase chain reaction—denaturing gradient gel electrophoresis (PCR-DGGE) and next-generation sequencing (NGS) revealed that the diverse microbial community in each consortium changed with subculture and became stable with a few effective microorganisms after 15 generations. The total petroleum hydrocarbons (TPH) degradation ability of the consortia obtained from a former gas station (C1: 81%) and oil refinery company (C6: 79%) was higher than that of the consortia obtained from wastewater treatment plant (WWTP) (C3: 67%, and C5: 73%), indicating that bacteria present in C1 and C6 were historically exposed to petroleum hydrocarbons. Moreover, it was intriguing that the consortium C4, also obtained from WWTP, exhibited high TPH degradation ability (77%). The NGS results revealed that two bacteria, Achromobacter sp. and Ochrobactrum sp., occupied more than 99% of the consortium C4, while no Pseudomonas sp. was found in C4, though this bacterium was observed in other consortia and is also known to be a potential candidate for TPH degradation as reported by previous studies. In addition, the consortium C4 showed high biosurfactant-producing ability among the studied consortia. To date, no study has reported the TPH degradation by the combination of Achromobacter sp. and Ochrobactrum sp.; therefore, the consortium C4 provided an excellent opportunity to study the interaction of and biosurfactant production by these two bacteria during TPH degradation.
Highlights
Soil and water pollution caused by petroleum and its derivatives are among the most severe global environmental problems because petroleum hydrocarbons are highly persistent in the environment, toxic, and pose serious health risks to humans [1,2]
We investigated the heavy oil degradation ability of six biosurfactant-producing bacterial consortia enriched from previously oil-spilled beach areas in Miyagi, Japan, and compared the microbial community structures of the studied consortia to reveal their potentiality in degradation while producing biosurfactants
The obtained DNA bands from DGGE depicted that the microbial community in all consortia changed after the 10th subculture to adapt and acclimate with the composition of the heavy oil
Summary
Soil and water pollution caused by petroleum and its derivatives are among the most severe global environmental problems because petroleum hydrocarbons are highly persistent in the environment, toxic, and pose serious health risks to humans [1,2]. It is known that chemical surfactants are nonbiodegradable and, have relatively high potential to cause toxicity to living organisms, hydrocarbon-degrading bacteria, and the surrounding environment. They can inhibit biodegradation via toxic interaction and sequestration of hydrocarbon into surfactant micelles and can cause a decrease in oxygen uptake rate [11]
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