Bioremediation is based on microorganisms able to use pollutants either as a source of carbon or in co-metabolism, and is a promising strategy in cleaning the environment. Using soil contaminated with petroleum products from an industrial area in Saudi Arabia (Jubail), and after enrichment with the polycyclic aromatic hydrocarbon (PAH) naphthalene, a Methylobacterium radiotolerans strain (N7A0) was isolated that can grow in the presence of naphthalene as the sole source of carbon. M. radiotolerans is known to be resistant to gamma radiation, and this is the fi rst documented report of a strain of this bacterium using a PAH as the sole source of carbon. The commonly reported Pseudomonas aeruginosa (strain N7B1) that biodegrades naphthalene was also identifi ed, and gas chromatography analyses have shown that the biodegradation of naphthalene by M. radiotolerans and P. aeruginosa did follow both the salicylate and phthalate pathways.
The exploitation of petroleum oil generates a considerable amount of “produced water or petroleum waste effluent (PWE)” that is contaminated with polycyclic aromatic hydrocarbons (PAHs), including Benzo[a]pyrene (BaP). PWE is characterised by its high salinity, which can be as high as 30% NaCl, thus the exploitation of biodegradation to remove PAHs necessitates the use of active halophilic microbes. The strain 10SBZ1A was isolated from oil contaminated soils, by enrichment experiment in medium containing 10% NaCl (w/v). Homology analyses of 16S rRNA sequences identified 10SBZ1A as a Staphylococcus haemoliticus species, based on 99.99% homology (NCBI, accession number GI: MN388897). The strain could grow in the presence of 4–200 μmol l-1 of BaP as the sole source of carbon, with a doubling time of 17–42 h. This strain optimum conditions for growth were 37 oC, 10% NaCl (w/v) and pH 7, and under these conditions, it degraded BaP at a rate of 0.8 μmol l-1 per day. The strain 10SBZ1A actively degraded PAHs of lower molecular weights than that of BaP, including pyrene, phenanthrene, anthracene. This strain was also capable of removing 80% of BaP in the context of soil spiked with BaP (10 μmol l-1 in 100 g of soil) within 30 days. Finally, a metabolic pathway of BaP was proposed, based on the identified metabolites using liquid chromatography-high resolution tandem mass spectrometry. To the best of our knowledge, this is the first report of a halophilic BaP degrading bacterial strain at salinity > 5% NaCl.
A bacterial consortium that degrades cooking oil (CO) has been isolated in wastewater (WW) samples, by enrichment in olive CO. This consortium could degrade 90% of CO within 7-9 days (from an initial 1% [w/v]), and it is more active at alkaline conditions. The 16S ribonucleic acid (RNA) gene analysis showed that it contains five bacterium species: Stenotrophomonas rhizophila, Sphingobacterium sp., Pseudomonas libanensis, Pseudomonas poae and Pseudomonas aeruginosa. This consortium can degrade the free fatty acids (FFA): palmitic, stearic, oleic, linoleic and linolenic acids; glycerol, glucose and amylose; and albumin, but could not efficiently degrade carboxymethyl-cellulose. Each strain could also degrade CO and FFAs. The level of bacterial crude-activity of extracellular lipases was found to be between 0.2 and 4U/ml. Using synthetic WW, the consortium could reduce 80% of the chemical oxygen demand [from 10550 ± 2828 mg/l], 80% of nitrogen (from 410 ± 78 mgl/l) and 57% of phosphorus (from 93 ± 25 mg/l). Thus, this consortium can be utilized in the removal of CO from WW.
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