Capability of Nocardia nova found in activated sludge to use synthetic BTEX as sole source of carbon and energy

Benzene and its derivatives, toluene, ethylbenzene and xylenes (BTEXs) are volatile monocyclic aromatic compounds which are widely distributed in nature and highly hazardous to human and animal health. The species belonging to the genus Nocardia are filamentous bacteria widely present in the flocs of activated sludge. They lead to the formation of foams and bulking sludge, which disrupt the sludge settling properties and thus reduce the quality of the purified water. The aim of our study is to isolate from these filamentous bacteria in the activated sludge, indigenous strains of Nocardia able to use the BTEX as the sole source of carbon and energy. Two isolation media were used to isolate the Nocardia species found in the activated sludge samples taken from the Ibn Ziad (Constantine-Algeria) wastewater treatment plant. The results show that five strains that morphologically resemble Nocardia have been isolated. The strain named (S) was identified by the sequencing of its 16S rRNA gene as Nocardia nova. This strain was the only isolate capable of growing under laboratory conditions, on BTE (m-o-p) X added at concentrations of 1500 mg/L each. Such a result can be used in the bioremediation of aquatic or terrestrial ecosystems contaminated by these compounds, using this bacterium as a bio-augmentation agent.