Identification of hydrocarbon-degrading bacterial consortium isolated from the oil-contaminated muddy soil in Hanoi, Vietnam

Abstract

Bioremediation is a promising approach for treating oil-contaminated environments. The main objective of this study was to isolate bacteria capable of degrading hydrocarbons for application in oily wastewater treatment from oil-contaminated sites in Hanoi, Vietnam. The bacterial consortium studied was obtained from an oil-contaminated muddy soil sample enriched with crude oil mixed with diesel oil as a carbon source. The reconstituted consortium was able to degrade 93% of the oil content after 7 days of testing. A total of five pure bacterial strains were isolated on TSA agar from the complex microbial communities and were selected as potential candidates for oily sludge biodegradation processes. These isolates were identified based on their morphological and biochemical characteristics. By using molecular biology techniques, five hydrocarbons degrading bacteria were investigated and identified as Pseudomonas mendocina strain MD1 (OL687411.1), Pseudomonas hydrolytica strain MD2 (OL771695.1), Brucella intermedia strain MD3 (OL687412.1), Pseudomonas stutzeri strain MD4 (OL687413.1), and Stenotrophomonas nitritireducens strain MD5 (OL687414.1). The morphological and biochemical characterization of these bacteria showed that five of them were Gram-negative, rod-shaped, catalase positive, the ideal pH was neutral, and the optimum growth temperature was 30ºC in a culture medium with a salinity of 0.5%. These strains are capable of producing extracellular enzymes, such as lipase, amylase, cellulase, and protease.