Bioremediation Case Study - Dr Louglin PDF

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Lecture Summary for Bioremediation Case Study (Dr Loughlin, Applied Microbiology '15/16)...

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Dr. Loughlin

Bioremediation Case Study: Oil Spillage 

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Petroleum hydrocarbons: low MW gases, higher MW liquids and soilds at RT o Saturates o Aromatics o Asphaltene: phenols, fatty acids, ketones, esters & porphyrins o Resins: pyrimidines, quinolones, sulphoxides, amides Oil bioremediation o Petroleum hydrocarbons = rich source of organic matter o Most susceptible:  N alkalines  Low MW aromatics o Harder to degrade:  Branched alkanes  Polycyclic aromatics Biochemistry of petroleum degradation: o Aromatic hydrocarbons o Pseudomonas bacteria o Degradation usually requires oxygenase enzymes which add oxygen to the aromatic ring  So reactions require oxygen  Genes encoding oxygenase enzymes are often on plasmids o Aliphatic hydrocarbon:  Used as electron donors (like glucose and other sugars)  Can also occur by carboxylation  Addition of CO2 under anoxic conditions to make a fatty acid  Fatty acid then oxidised by B-oxidation to acetyl Co-A  Ring structures tougher o Oxygenases: Add O from O2 to an aromatic ring o Mono-oxygenase: Add one O, the other is reduced to H2O

o DI-oxygenase: Both O from O2 added to the ring

Dr. Loughlin o Sequential Dioxygenase:

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o End products such as catechol can be incorporated into metabolism and transformed to succinate, acetyl Co-A or pyruvate o Eventually, hydrocarbons are oxidised to CO2 Oil Bioremediation: o Oil state:  Oil spill on soil or into sediment from water  Vertical movement………………… through soil  Prevents ……………………. losses (no loss of C12 compounds) o Toxic hydrocarbons:  Toxic to hydrocarbon degrading bacteria  Slower bioremediation… lower ………..levels  Bacteria with oxygenase enzymes may be unable to bioremediate without O2  So bacteria not present Effects of an oil spill: o Fish Toxicity o Sea birds o Sea mammals o Plankton o Shorelines o Invertebrates Oil is insoluble and less dense than water  floats on water Wave action  plenty of oxygen Oil in water or water in oil emulsion Non-bioremediation methods: o Physical containment o Burning o Dispersant o Water jets (shoreline) Oil Bioremediation: o Microbial biosurfactants:  Peptides, lipids, saccharides  Amphipathic with MW typically 500-1500 Da  Reduce surface tension  Increase surface area for attack  96% of hydrocarbon producing bacteria o Artificial Surfactants  Must be environmentally friendly

Dr. Loughlin

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 Torrey Canyon disaster, Cornwall 1967  No longer use napalm and toxic detergents o Supplementing natural population with GM Bacteria  Key enzymes (oxygenases)  Known organisms added to environment  But concern over uncontrolled release of GMOs o Optimising environmental conditions  Maximise indigenous degrading microbes (already have oxygenases)  Fertiliser addition (P, N often limiting in marine envt)  Nitrogen fertilisers used extensively in Exxon Valdez incident  Dispersants to increase amount of hydrocarbon-water interface Comparing Exxon Valdez & Deepwater: o Deepwater 10X more oil spilled, plus methane, from 1500 m underwater. Light crude so more easily degraded. o Gulf of Mexico open and exposed, many natural oil seeps and other drilling rig spills. Spill was 77 km offshore. o Exxon Valdez surface water slick, near shore, heavy crude o Alaskan site pristine, shallow and enclosed. Spill close to shore. o So treatments used were very different o BP Deepwater Horizon = largest ever remediation & emergency response to an oil spill worldwide...