Biodegradation of Crude Oil under Various Redox Conditions

The conventional approach to bioremediation of petroleum hydrocarbon is based on aerobic processes.  Anaerobic bioremediation has been tested only in a very few cases and is still considered experimental. The currently practiced conventional in-situ biorestoration of petroleum-contaminated soils, and ground water relies on the supply of oxygen to the sub-surface to enhance natural aerobic processes to remediate the contaminants.  However, anaerobic microbial processes can be significant in oxygen-depleted sub-surface environments and sediments that are contaminated with petroleum-based compounds such as oil-impacted marshes in Louisiana.  The goal of this work was to identify the right conditions for the indigenous anaerobic bacteria present in the BP-oil contaminated sites to enhance degradation of petroleum hydrocarbons.  We evaluated the ability of microorganisms under a variety of electron acceptor conditions to degrade petroleum hydrocarbons. Researched microbial systems include sulfate-, nitrate-reducing bacteria, and fermenting bacteria.  The results indicated that anaerobic bacteria are viable candidates for bioremediation. Enhanced biodegradation was attained under mixed electron acceptor conditions, where various electron-accepting anaerobes co-existed and aided in degrading complex petroleum hydrocarbon components of marsh sediments in the coastal Louisiana.  Significant degradation of oil also occurred under sulfate reducing and nitrate reducing conditions.