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. Toluene degradation TCE degradation
T2MO
T3MO
TOD
toluene-cis-
dihydrodiol
dehydrogenase
catechol-2,3
3-methylcatechol
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,
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