Biodegradation of used motor oil by Streptomyces ginkgonis KM-1–2, isolated from soil polluted by waste oils in the region of Azzaba (Skikda-Algeria)

Actinobacteria have many properties that make them good candidates for the bioremediation of sites contaminated by several organic and inorganic pollutants. However, studies on the biodegradation of used motor oils by Actinobacteria, compared to other bacteria, remain little studied. Actinobacteria were isolated from soil contaminated with used motor oils and sewage sludge in order to select a species that can effectively degrade such pollutants. This study aims to assess their degradation capacity of the various hydrocarbon fractions contained in the oil by gas chromatography-mass spectrometry (GC-MS). Five Actinobacteria isolates were isolated by the enrichment method. The S1.1. A strain was considered the best biosurfactant producing strain. It presents the highest emulsification index compared to other isolated Actinobacteria (82.6%). Phenotypic and molecular identification by sequencing the 16 S rDNA gene makes it possible to assign this isolate to the species Streptomyces ginkgonis KM-1–2. Gravimetric analysis results of biodegraded used motor oil indicated that this strain is capable of degrading 76.4% of an initial 50 ml/l concentration of used motor oil after 4 weeks of incubation. The results of GC-MS analysis of the residual motor oil showed that strain S1.1. A degraded some long and intermediate chain alkanes completely or to shorter fractions. The Streptomyces ginkgonis strain KM-1–2 was also able to degrade certain alkylated mono-aromatic hydrocarbons linked to benzene, as well as certain alkylated and non-alkylated polycyclic aromatic hydrocarbons linked to anthracene, naphthalene, phenanthrene, fluorene, and azulene. This strain exhibited the highest emulsification index at 82.6%. This bacterium shows a significant biodegradation capacity and could, consequently, be used in the processes of bioaugmentation of sites contaminated by these oils.