Isolation and Characterization of Oil-Degrading Enterobacter sp. from Naturally Hydrocarbon-Contaminated Soils and Their Potential Use against the Bioremediation of Crude Oil

Abstract

The contamination of crude oil in soil matrices is a persistent problem with negative repercussions because of the recalcitrant, hazardous, and mutagenic properties of its constituents. To mitigate the effect of crude oil contamination in soil, the use of microorganisms is a cheap and feasible option. In the current study, bacterial species from numerous polluted oil field surfaces were isolated and examined for their ability to degrade crude oil. Random soil samples polluted with hydrocarbons were collected and various bacterial isolates were isolated. Results revealed that 40% of total isolates had potential use for hydrocarbon biodegradation, the synthesis of exopolysaccharides and the solubilization of phosphorous. Following isolation and characterization to degrade crude oil, a pot trial was conducted using maize inoculated with the four best strains—i.e., S1 (PMEL-63), S2 (PMEL-67), S3 (PMEL-80), and S4 (PMEL-79)—in artificially hydrocarbon-polluted soil with concentrations of crude oil of 0, 1000, and 2000 ppm. Results revealed that S4 (PMEL-79) had significant potential to degrade hydrocarbon in polluted soils. The root length, shoot length, and fresh biomass of maize were increased by 65%, 45%, and 98%, respectively, in pots inoculated with S4 (PMEL-79) Enterobacter cloacae subsp., whereas the lowest root length was observed where no strain was added and the concentration of crude oil was at maximum. Moreover, S4 (PMEL-79) Enterobacter cloacae subsp. was found to be the most effective strain in degrading crude oil and increasing maize growth under polluted soil conditions. It was concluded that the isolation of microorganisms from oil-contaminated sites should be considered in order to identify the most effective microbial consortium for the biodegradation of naturally hydrocarbon-contaminated soils.