Biodegradation of used engine oil by lead-resistant bacteria Acinetobacter sp.HAR20 newly isolated from harbour seawater (Oran, Algeria).

This paper focuses on the degrading capacity of various hydrocarbon fractions of used engine oils (UEO) by marine microorganisms, as well as the biosorption of heavy metals. A bacterial strain with a significant capability to grow on UEO as a sole source of carbon and energy was isolated from harbour seawater samples (Oran, Algeria). The molecular identification by sequencing the 16S rDNA gene revealed that the bacterium matched Acinetobacter baumanii with 96.84% homology similarity. Thus, strain HAR20 was named Acinetobacter sp.HAR20. The degradation rate of UEO (at 1%, v/v) obtained after 15 days of incubation was about 53.4 ± 4.2%. The results of GC-MS analysis of the biodegraded residual motor oil indicate that strain Acinetobacter sp.HAR20 degrades alkanes with chain lengths ranging from C4 to C48 completely or to shorter fractions. The bacterium was also able to degrade all aromatic compounds of UEO, including polycyclic aromatic hydrocarbons (alkylated and no alkylated naphthalene, alkylated phenanthrene, and fluorene). The strain Acinetobacter sp.HAR20 exhibited different degrees of resistance to the heavy metals tested (Cd, Zn, Ni, Cu, Fe, and Pb). The highest tolerance was obtained for Pb (600 mg.l⁻¹). The study of lead biosorption at a concentration of 300 mg.l⁻¹ revealed that the bacterium displayed a removal rate of 57.47 ± 7.5%. The strain Acinetobacter sp.HAR20 has shown an interesting biodegradation potential; therefore, it could be proposed as a choice for the bioremediation of contaminated seawater by used engine oils. [ABSTRACT FROM AUTHOR]