A new Rhodococcus aetherivorans strain isolated from lubricant-contaminated soil as a prospective phenol-biodegrading agent

Abstract

Microbe-based decontamination of phenol-polluted environments has significant advantages over physical and chemical approaches by being relatively cheaper and ensuring complete phenol degradation. There is a need to search for commercially prospective bacterial strains that are resistant to phenol and other co-pollutants, e.g. oil hydrocarbons, in contaminated environments, and able to carry out efficient phenol biodegradation at a variable range of concentrations. This research characterizes the phenol-biodegrading ability of a new actinobacteria strain isolated from a lubricant-contaminated soil environment. Phenotypic and phylogenetic analyses showed that the novel strain UCM Ac-603 belonged to the species Rhodococcus aetherivorans, and phenol degrading ability was quantitatively characterized for the first time. R. aetherivorans UCM Ac-603 tolerated and assimilated phenol (100% of supplied concentration) and various hydrocarbons (56.2–94.4%) as sole carbon sources. Additional nutrient supplementation was not required for degradation and this organism could grow at a phenol concentration of 500 mg L−1 without inhibition. Complete phenol assimilation occurred after 4 days at an initial concentration of 1750 mg L−1 for freely-suspended cells and at 2000 mg L−1 for vermiculite-immobilized cells: 99.9% assimilation of phenol was possible from a total concentration of 3000 mg L−1 supplied at daily fractional phenol additions of 750 mg L−1 over 4 days. In terms of phenol degradation rates, R. aetherivorans UCM Ac-602 showed efficient phenol degradation over a wide range of initial concentrations with the rates (e.g. 35.7 mg L−1 h−1 at 500 mg L−1 phenol, and 18.2 mg L−1 h−1 at 1750 mg L−1 phenol) significantly exceeding (1.2–5 times) reported data for almost all other phenol-assimilating bacteria. Such efficient phenol degradation ability compared to currently known strains and other beneficial characteristics of R. aetherivorans UCM Ac-602 suggest it is a promising candidate for bioremediation of phenol-contaminated environments.

Fatty Acid Composition of Rhodococcus aetherivorans Cells During Phenol Assimilation

“…Among the members of this genus, R. aetherivorans is a species of special interest in the biodegradation of various resistant to degradation pollutants, such as noncyclic and cyclic ethers [18][19][20], aliphatic and aromatic hydrocarbons [21] and chlorinated organic compounds [22]. Our previous studies have shown that R. aetherivorans UCM Ac-602 strain efficiently degraded phenol as well as n-hexadecane, kerosene, diesel fuel and transformer oil [7]. It is known that changes in the lipid composition of cells, primarily fatty acids, are of great importance in the adaptation of microorganisms to the assimilation of membraneactive compounds, in particular phenol and its derivatives [3,8,9,11].…”

“…To assess the effect of phenol on fatty acid composition of R. aetherivorans UCM Ас-602 compared to that on n-hexadecane or glucose, the fatty acid profiles of cells were compared in cultures reaching the stationary growth phase at cultivation on these substrates. In previous studies, we have shown that R. aetherivorans UCM Ас-602 cells grown at a phenol concentration of 0.75, 1.0 and 1.5 g/L as a sole carbon and energy source reached the stationary growth phase and completely degraded phenol after 24, 48 and 72 h respectively [7]. Samples of control cells grown on the same medium with n-hexadecane and glucose were taken after 72 and 24 hours, respectively, until the cultures reached the stationary growth phase.…”

“…The object of the study was R. aetherivorans UCM Ac-602 strain which is maintained in the Ukrainian Collection of Microorganisms (UCM) of Danylo Zabolotny Institute of Microbiology and Virology of the NAS of Ukraine. The strain was isolated in our previous studies from lubricant contaminated soil at the locomotive depot of Odessa railway station as an active destructor of phenol and hydrocarbons [7,14].…”

“…In our earlier studies, we established the ability of Rhodococcus aetherivorans UCM Ac-602 strain to completely degrade a high concentration of phenol (up to 2000 mg/L) as the only source of carbon and energy, as well as its ability to actively assimilate oil hydrocarbons, in particular, n-hexadecane [7]. It is well known that phenol is a major pollutant of the environment and it is toxic for bacterial cells even at low concentrations.…”

Biodegradation of Phenol by Rhodococcus sp. Strain SKC: Characterization and Kinetics Study

“…Due to its high toxicity to life and overall chemical stability, phenol frequently causes the breakdown of wastewater treatment plants [ 2 , 3 ]. Thus, phenol has been listed as one of 126 priority pollutants by the US Environmental Protection Agency [ 4 ]; the maximum phenol content in drinking water should be below 1.0 μg/L [ 5 ].…”