Biodegradation of n-Hexadecane in Acinetobacter Radioresistens Liquid Culture

Biodegradation of aliphatic and aromatic hydrocarbons by bacteria isolated from Bahregan area

Environmental pollution with aromatic and aliphatic hydrocarbons caused by oil and petrochemical industries has very toxic and carcinogenic effects on living organisms and should be removed from the environment. In this research, after analyzing the oil sludge of the Bahregan area, it was found that most aliphatic paraffin compounds are related to octadecane, most liquid aliphatic compounds are related to hexadecane, and most aromatic compounds are related to naphthalene, phenanthrene, fluoranthene, and anthracene. Then, we investigated the ability of native bacteria from this area, such as Thalassospira, Chromohalobacter, and a bacterial consortium, to biodegrade the dominant aromatic and aliphatic hydrocarbons found in oil sludge. The results of Gas Chromatography-Mass Spectrometry analysis showed that among the tested hydrocarbon sources, Thalassospira can completely remove octadecane and hexadecane, and Chromohalobacter can reduce hexadecane from 15.9 to 9.9%. The bacterial consortium can completely remove octadecane and reduce hexadecane from 15.9 to 5.1%, toluene from 25.6 to 0.6%, and phenanthrene from 12.93 to 6%. According to the obtained results, the bacterial consortium effectively plays a role in the biodegradation of aromatic and aliphatic hydrocarbons, making it a viable solution for treating hydrocarbon pollutants in various environments.

Cultivable fungi from deep-sea oil reserves in the Gulf of Mexico: Genetic signatures in response to hydrocarbons

The estimation of oil spill effects on marine ecosystems is limited to the extent of our knowledge on the autochthonous biota. Fungi are involved in key ecological marine processes, representing a major component of post-spill communities. However, information on their functional capacities remains lacking. Herein we analyzed cultivable fungi from sediments in two oil-drilling regions of the Gulf of Mexico for their ability to tolerate and use hexadecane and 1-hexadecene as the sole carbon sources; and to evaluate gene expression profiles of key hydrocarbonoclastic taxa during utilization of these hydrocarbons. The isolated fungi showed differential sensitivity patterns towards the tested hydrocarbons under three different concentrations. Remarkably, six OTUs (Aureobasidium sp., Penicillium brevicompactum, Penicillium sp., Phialocephala sp., Cladosporium sp. 1 and 2) metabolized the tested alkane and alkene as the sole carbon sources, confirming that deep-sea fungal taxa are valuable genetic resources with potential use in bioremediation. RNA-seq results revealed distinctive gene expression profiles in the hydrocarbonoclastic fungus Penicillium sp. when using hexadecane and 1-hexadecene as the sole carbon sources, with up-regulation of genes involved in transmembrane transport, metabolism of six-carbons carbohydrates, and nitric oxide pathways.

Biodegradation of diesel oil by a novel microbial consortium: comparison between co-inoculation with biosurfactant-producing strain and exogenously added biosurfactants

Bioremediation, involving the use of microorganisms to detoxify or remove pollutants, is the most interesting strategy for hydrocarbon remediation. In this aim, four hydrocarbon-degrading bacteria were isolated from oil-contaminated soil in Tunisia. They were identified by the 16S rDNA sequence analysis, as Lysinibacillus bronitolerans RI18 (KF964487), Bacillus thuringiensis RI16 (KM111604), Bacillus weihenstephanensis RI12 (KM094930), and Acinetobacter radioresistens RI7 (KJ829530). Moreover, a lipopeptide biosurfactant produced by Bacillus subtilis SPB1, confirmed to increase diesel solubility, was tested to increase diesel biodegradation along with co-inoculation with two biosurfactant-producing strains. Culture studies revealed the enhancement of diesel biodegradation by the selected consortium with the addition of SPB1 lipopeptide and in the cases of co-inoculation by biosurfactant-producing strain. In fact, an improvement of about 38.42 and 49.65 % of diesel degradation was registered in the presence of 0.1 % lipopeptide biosurfactant and when culturing B. subtilis SPB1 strain with the isolated consortium, respectively. Furthermore, the best improvement, evaluated to about 55.4 %, was recorded when using the consortium cultured with B. subtilis SPB1 and A. radioresistens RI7 strains. Gas chromatography analyses were correlated with the gravimetric evaluation of the residual hydrocarbons. Results suggested the potential applicability of the selected consortium along with the ex situ- and in situ-added biosurfactant for the effective bioremediation of diesel-contaminated water and soil.