Bioremediation

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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
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Bioremediation as Part of All Remediation
Technologies
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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

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Bioremediated Contaminants
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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/Biodegrad
ation Database, http//umbbd.ahc.umn.edu/

• Organisms that contain these oxygenases will
  detoxify toluene, TCE, and many other aromatic
  and chlorinated toxic compounds

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How Does Contamination Occur?
Spills or leaks sink into soil or water Get
transported by water movement
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Contaminants get Dispersed
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Plumes of Contaminants Remain
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Plumes of Contaminants Remain
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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 ---gt population increases --gtget
  degradation of TCE
• Oil spills just need to add a N and P source

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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

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Access to Contaminants
No surfactants
With surfactants
Add genes to synthesize surfactants
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Problems with Genetically Engineered
Microorganisms (GEMs)

• Dont survive in the environment
• Cant 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