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Limits to Petroleum Degradation

Explore the crucial factors and processes that often restrict in situ petroleum hydrocarbon degradation, from electron acceptors to biodegradation pathways and field studies. Learn about common limitations and relevant biocatalytic reactions.

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Limits to Petroleum Degradation

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  1. Limits to Petroleum Degradation Name the 3 most common things that most often limit in situ petroleum hydrocarbon degradation • Nitrogen • Phosphorus • Oxygen

  2. Oxidation/Reduction Reactions • Hydrocarbon biodegradation is essentially an oxidation/reduction reaction • Hydrocarbon is oxidized and Electron acceptor is reduced hydrocarbon + electron acceptor + microorganisms + nutrients  carbon dioxide + microorganisms + waste products Electron acceptors include: O2, NO3-, iron oxides (Fe(OH)3), SO42-, H2O

  3. Aerobic Degradation • Aerobic bacteria use O2 as their terminal electron acceptor • Water saturated with air contains 6 – 12 mg/L dissolved O2 • Complete conversion of hydrocarbons to CO2 and H2O requires ~3 mg/L of O2 for each 1 mg/L hydrocarbon • Maximum of 12 mg/L dissolved O2 = maximum 4 mg/L hydrocarbon degradation • Unlikely to have saturated dissolved O2

  4. Organic Chemistry polycyclic aromatic hydrocarbon monocyclic aromatic hydrocarbons primary alkane biphenyl type benzenoid ring organohalide nitro compound

  5. BTEX Benzene, Toluene, Ethylbenzene, Xylene • Volatile monoaromatic hydrocarbons • Commonly found together in crude petroleum and petroleum products such as gasoline • Major cause of environmental pollution • LUSTs: leaking underground storage tanks • ~35% of 1.4 million gas storage tanks in the US are leaking

  6. Biocatalysis/Biodegradation Database http://umbbd.ahc.umn.edu Microbial biocatalytic reactions and biodegradation pathways primarily for xenobiotic, chemical compounds.

  7. Aerobic BTEX Degradation • Pseudomonads: chemoorganotrophs, aerobic, rod-shaped bacteria • Important genera are: Pseudomonas, Burkhoderia, and sometimes Xanthomonas • Isolated from the environment • Some are pathogenic • 1968: strain of Pseudomonas putida isolated • grew on ethylbenzene, benzene, and toluene • toluene dioxygenase!

  8. Toluene Dioxygenase -Catalyzes over 108 reactions 1. Monocyclic aromatics 2. Fused Aromatics 3. Linked aromatics 4. Miscellaneous

  9. Anaerobic BTEX Degradation • Wide variety of microorganisms • Denitrifiers, example is Thauera aromatica • Iron Reducers • Sulfate reducers, examples are Desulfovibrio, Desulfobacter • Methanogens • Usually requires a consortium

  10. Field Studies • Crude oil study in MN in 2000 • Buried oil pipeline ruptured in 1979 = 3200 barrels of oil spilled into subsurface • Growth of aquifer microbial populations (dominated by aerobes, iron reducers, methanogens) • Biodegradation caused a number of FOOTPRINTS near the plume = geochemical changes What might FOOTPRINTS be???

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