Isolation and Characterization of Diesel-Degrading Bacteria from Hydrocarbon-Contaminated Sites, Flower Farms, and Soda Lakes.

Gessesse Kebede Bekele,Mesfin Tafesse,Tekle Tafese Fida,Fasil Assefa,Ebrahim M Abda,Eshetu Mekonen,Adugna Abdi Woldesemayat,Solomon Abera Gebrie,Todd R Callaway

doi:10.1155/2022/5655767

Abstract

Hydrocarbon-derived pollutants are becoming one of the most concerning ecological issues. Thus, there is a need to investigate and develop innovative, low-cost, eco-friendly, and fast techniques to reduce and/or eliminate pollutants using biological agents. The study was conducted to isolate, characterize, and identify potential diesel-degrading bacteria. Samples were collected from flower farms, lakeshores, old aged garages, asphalt, and bitumen soils and spread on selective medium (Bushnell Haas mineral salt agar) containing diesel as the growth substrate. The isolates were characterized based on their growth patterns using optical density measurement, biochemical tests, and gravimetric analysis and identified using the Biolog database and 16S rRNA gene sequencing techniques. Subsequently, six diesel degraders were identified and belong to Pseudomonas, Providencia, Roseomonas, Stenotrophomonas, Achromobacter, and Bacillus. Among these, based on gravimetric analysis, the three potent isolates AAUW23, AAUG11, and AAUG36 achieved 84%, 83.4%, and 83% diesel degradation efficiency, respectively, in 15 days. Consequently, the partial 16S rRNA gene sequences revealed that the two most potent bacterial strains (AAUW23 and AAUG11) were Pseudomonas aeruginosa, while AAUG36 was Bacillus subtilis. This study demonstrated that bacterial species isolated from hydrocarbon-contaminated and/or uncontaminated environments could be optimized to be used as potential bioremediation agents for diesel removal.

Highlights

Hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), benzene, kerosene, and diesel are important organic pollutants and inputs for different industries, vehicles, and household activities as a source of energy [1,2,3,4,5,6,7,8]
Nineteen dieseldegrading bacteria were isolated from the enrichment culture of different sampling sites (Table 1). e data showed that diesel-degrading bacteria were recovered from old aged asphalt sites, garage sites, and bitumen soil, which was expected to have exposure to hydrocarbon contamination, and from Gallica flower farm, which uses different agrochemicals containing polycyclic hydrocarbons
B. subtilis (AAUG36) was identified as a potent bacterial species for the degradation of diesel. e study showed that this species can be found in different environments due to its ability to produce endospores to pass harsh environments [13, 22] and surface-active substances to decrease surface and intersurface tension and increase the bioavailability of contaminants for efficient biodegradation [22]. is biological characteristic is important to augment the bioavailability of poorly accessible diesel and to enhance the biodegradation rate. erefore, this study indicated that P. aeruginosa and B. subtilis showed maximum degradation with a higher concentration of diesel (5%) and without using any synthetic surfactants

Summary

Introduction

Hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), benzene, kerosene, and diesel are important organic pollutants and inputs for different industries, vehicles, and household activities as a source of energy [1,2,3,4,5,6,7,8]. Diesel is massively used for engine, fuel, and industrial applications It is one of the products of petroleum compounds formed during fractional distillation of crude oil and is composed of a mixture of carbon chains between 9 and 25 carbon atoms that may include both aromatic and aliphatic hydrocarbon components [4, 6, 9]. Biostimulation, engages the amendment of macro- and micronutrients, sustains physical parameters (pH, temperature, and aeration), and supplies surface-active substances (surfactants) in contaminated sites to optimize soil conditions and enhance biodegradation by increasing the growth rate of indigenous (naturally occurring) hydrocarbon-degrading microorganisms [4, 6, 11, 17, 18, 22, 29]. Biostimulation, engages the amendment of macro- and micronutrients, sustains physical parameters (pH, temperature, and aeration), and supplies surface-active substances (surfactants) in contaminated sites to optimize soil conditions and enhance biodegradation by increasing the growth rate of indigenous (naturally occurring) hydrocarbon-degrading microorganisms [4, 6, 11, 17, 18, 22, 29]. is technique can be applied in situ and ex situ [28] to enhance biodegradation by increasing the bioavailability of the pollutants and the growth rate of native (indigenous and autochthonous) hydrocarbon-degrading microorganisms [23]. us, potential microbes use hydrocarbonderived pollutants as a source of carbon and energy [27, 30] and/or cometabolites, leading to the complete mineralization of contaminants to carbon dioxide, water, mineral salts, and biomass [2, 3, 11, 13, 19, 25, 31]

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