Introduction . Examples Of Chloroaromatics. Methods of biodegradation. Microbial pathways for biodegradation. advantages. Disadvantages.

1. Al-neelain University
Faculty of Science and Technology
Department of Microbiology and Molecular Biology
Biodegradation Of Chloroaromatic
By:
Hatim Ahmed Mohamed Eissa

2. Biodegradation Of Chloroaromatic Compounds
Introduction:
Chlorinated aromatic compounds are only rarely synthesized
in nature, but are produced widely through human
activities in large quantities for various purposes.
• Chlorinated aromatic hydrocarbons are widely used in
industry and agriculture, and comprise the bulk of
environmental pollutants.
• Although simple aromatic compounds are biodegradable by a
variety of degradative pathways.

3. Biodegradation Of Chloroaromatic Compounds
• Their halogenated counterparts are more resistant to bacterial
attack.
• Chlorinated aromatic compounds are the major pollutants of
the environment because of their extensive use and toxicity.

4. Examples of chloroaromatics
 chlorobenzene .
 chlorophenol .

5. Methods of biodegradation:
1. Naturally isolated microorganisms .
Pseudomonas putida
Pseudomonas putida has been reported to grow on chlorobenzene
using a meta-cleavage pathway with chlorocatechol 2,3-
dioxygenase .
2. Geneyically modified microorganism.

6. Microbial pathways for biodegradation:
• some bacterial strains have evolved degradative pathways
for chloroaromatics and can even use these compounds as
growth substrates .
 Meta cleavage Pathway .
 Modified Ortho-cleavage Pathway
In general, under aerobic conditions, the CAs are
transforme via oxidative dechlorination, while in
anaerobic via reductive dechlorination.

7. Cont...
• The aerobic microbial degradation of various chloroaromatic
compounds occurs via chlorocatechols as central intermediates.
• a strictly anaerobic Gram-negative sulfate-reducing bacterium, is the
best-described dechlorinating .
• The basidiomycete Phanerochaete chrysosporium that commonly is known
as a
white rot fungus, can mineralize a variety of hazardous organic
chemicals including chlorinated phenols.

8. advantages
• Low cost .
• Cost efficient.
• Don in site.

9. disadvantages
• In high concentration less effective.
• So expensive when dealing with genetically modified
microorganism.
• Need monitoring.

10. disadvantages
• In high concentration less effective.
• So expensive when dealing with genetically modified
microorganism.
• Need monitoring.