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Bioremediation

Bioremediation. Use of bacteria to clean up (detoxify) pollution Contained wastes (in a factory, in tanks) Contaminated sites soil Water Other technologies also available VERY EXPENSIVE. Tanks at Hanford. Bioremediation as Part of All Remediation Technologies. Biodegradable Contaminants.

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Bioremediation

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  1. Bioremediation • Use of bacteria to clean up (detoxify) pollution • Contained wastes (in a factory, in tanks) • Contaminated sites • soil • Water • Other technologies also available • VERY EXPENSIVE Tanks at Hanford

  2. Bioremediation as Part of All Remediation Technologies

  3. Biodegradable Contaminants • Bacteria have the natural ability to either grow on toxic compounds or convert them to nontoxic products • Classes of contaminants biodegraded • Aromatics (toluene, xylene, benzene, phenol, naphthalene) • Chlorinated aromatics (chlorobenzene, PCBs) • Chlorinated solvents (chloroform, trichloroethylene [TCE]) These mostly involve enzymes called oxygenases • Toxic metals (mercury) • Other toxic metals can be taken up or precipitated by cells • Cu, Co, Ni, Pb • Not detoxified but can be removed more easily

  4. Bioremediated Contaminants

  5. T2MO T3MO TOD T2MO T3MO toluene-cis- dihydrodiol dehydrogenase 3-methylcatechol catechol-2,3 dehydrogenase Toluene degradation TCE degradation sMMO T2MO TOD TCE epoxide glyoxylate formate chloral hydrate (not in whole cells) sMMO T2MO (only with sMMO) dichloroacetate glyoxylate formate The University of Minnesota Biocatalysis/Biodegradation Database, http://umbbd.ahc.umn.edu/ • Organisms that contain these oxygenases will detoxify toluene, TCE, and many other aromatic and chlorinated toxic compounds

  6. How Does Contamination Occur? Spills or leaks sink into soil or water Get transported by water movement

  7. Contaminants get Dispersed

  8. Plumes of Contaminants Remain

  9. Plumes of Contaminants Remain

  10. Natural Bioremediation • Problem: how to get bacteria to contaminant? • Natural strains have biodegradative capability • Can use in situ populations • Need to increase total population by adding substrates • Contaminated sites often very low nutrient • Contain mixed populations of bacteria • Gram of soil can contain 109 bacteria • 1000s of types (tremendous diversity) • Stimulate specific types with specific nutrients • Example: bacteria that grow on methane accidentally detoxify TCE • add methane ---> population increases -->get degradation of TCE • Oil spills: just need to add a N and P source

  11. What is Role for Engineering Bacteria? • Increase substrates detoxified • More individual compounds detoxified by one strain • Simultaneous detoxification • Increase rate of detoxification • Increase expression • Increase access to hydrophobic contaminants • If contaminant can be accessed, it will not persist • Hydrophobic contaminants persist

  12. Access to Contaminants No surfactants With surfactants Add genes to synthesize surfactants

  13. Problems with Genetically Engineered Microorganisms (GEMs) • Don’t survive in the environment • Can’t compete with existing bacteria • Cloning in survival or persistence genes raises regulatory issues • Few field trials of GEMs, identified strains that can persist • Greatest potential of GEMs for bioremediation is contained waste

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