Biodegradation of crude oil by nitrogen fixing marine bacteria azotobacter chroococcum

The present study deals with the hydrocarbon degrading potential of a marine nitrogen fixing bacterium Azotobacter chroococcum isolated from Tuticorin harbor (Lat. 08°45'N; Long. 78°13'E). Degradation of crude oil (58%) and emulsification (D ₆₁₀) of waste motor oil (1.51), crude oil (1.43), pea nut oil (1.39), diesel (0.69), kerosene (0.81), Naphthalane (0.36), Anthracene (0.33) and xylene (0.42) indicated its potentiality in utilization of various hydrocarbons. Growth of Azotobacter chroococcum in a mineral medium with 0.5% crude oil as sole carbon source resulted maximum cell density at 96 h with an OD value of 0.333. At the end of 96 h, the cell count was 4.5×10 ⁹ CFU mL ^-1 and 2.5 mg mL ^-1 of biomass. The biosurfactant production was found to be 1 mg mL ¹ at 96 h. The total nitrogen fixed was 4.2 mg L ^-1. Two plasmids were found with molecular weight of 4788 and 2400 base pairs, respectively. Loss of biodegradation and biosurfactant production after plasmid curing was observed, which confirmed that, the biosurfactant production and biodegradation process were plasmid mediated. Results of the present study revealed the possibility of using marine nitrogen fixing hydrocarbon degrading bacteria and their biosurfactants in the abatement of marine oil pollution.