Bioremediation potential of native hydrocarbon degrading bacterial strains in crude oil contaminated soil under microcosm study

•Isolation, characterization of crude oil bacteria from oil contaminated soils of Assam.•Three Pseudomonas species and Achromobacter xyloxidans highest crude oil degrader.•Screened bacteria showed reclamation of crude oil contamination soil.•Formulations BF1-Mix, BF2-Mix is effective in reclamation of crude oil contamination environment.•Bioassay confirmed complete recovery of reclaimed crude oil contaminated soil.

Bioremediation of crude oil contaminated soil is an effective process to clean petroleum contaminant from the environment. In this study, we isolated 39 native crude oil degrading bacteria from different crude oil contaminated soils. From 16S rDNA sequences, we confirmed that the isolated bacteria belong to the genera Lysinibacillus, Brevibacillus, Bacillus, Paenibacillus, Stenotrophomonas, Alcaligenes, Delftia, Achromobacter and Pseudomonas. Four most effective strains (designated as AS03, N108, N002 and N78) were used for batch culture and microcosm evaluation. Gas chromatography analysis, further confirmed that the strain AS03, N108, N002 and N78 were able to degrade crude oil under both shake culture and microcosm study. Under microcosm, the soil quality was further improved significantly in the treatments of BF1-Mix (N108-AS03) and BF2-Mix (N002-N78). The improvement of soil quality was also confirmed by earthworm mortality bioassay and in plant test on rice (Oryza sativa) and mung (Vigna radiata). These findings demonstrated that the combine use of crude oil degrading bacteria along with nutrient supplements could revive crude oil contaminated soil effectively in large scale.