esm222_17_biodegradation

Esm222_17_biodegrada - ESM 222 Biological Degradation Biodegradation involves the transformation of organic pollutants enzyme-catalyzed reactions

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1 © Arturo A. Kel er ESM 222 Biological Degradation 2 © Arturo A. Kel er Biological Degradation ± Biodegradation involves the transformation of organic pollutants ± enzyme-catalyzed reactions ± Inorganic pollutants (e.g. Fe 2+ , Pb 2+ ,NO 3- , NH 4+ ) may also be used by microorganisms and plants ± for oxidation/reduction reaction ± generally do not remove inorganic pollutant from environment 3 © Arturo A. Kel er Biological Degradation ± Biological transformations ± Can accelerate by several orders of magnitude the rate of transformation of a pollutant ± Enzymes lower the activation energy required for a reaction ± Provide a surface where pollutant and oxidant can meet 4 © Arturo A. Kel er Biological Degradation 5 © Arturo A. Kel er Biological Degradation ± The organic pollutant may be degraded ± as a substrate (i.e. a good food source), usually as a carbon source ± via cometabolism (i.e. the bugs generally prefer something else but have the enzymes to partially degrade the pollutant) 6 © Arturo A. Kel er Biological Degradation
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7 © Arturo A. Kel er Biological Degradation ± A major issue in biodegradation is “bioavailability”: ± Is the pollutant available to the microorganisms for degradation? ± Is it dissolved? ± Can they use a sorbed pollutant? 8 © Arturo A. Kel er Biological Degradation 9 © Arturo A. Kel er Biological Degradation ± Microbes have enzymes inside and outside (exoenzymes) of the cell wall ± Not all microbes carry the necessary enzymes for degradation of all pollutants ± Pollutants with unusual chemical structures will not be easily degraded 10 © Arturo A. Kel er Biological Degradation 11 © Arturo A. Kel er Biological Degradation ± Some enzymes are very specific to a particular chemical and do not serve to degrade/transform other molecules ± Other enzymes are non-specific and result in the “chance” transformation of pollutants - this is the explanation for cometabolism 12 © Arturo A. Kel er Biological Degradation ± Example: degradation of TCE ± Methanothrops (methane eaters) have an enzyme, denominated Methane Monooxygenase (MMO), which is quite non-specific ± MMO is also used by bacteria to degrade most hydrocarbons
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13 © Arturo A. Kel er Biological Degradation 14 © Arturo A. Kel er Biological Degradation ± In general, one microorganisms will not be responsible for the complete degradation of the pollutant to CO 2 , H 2 0 (and Cl - , NH 4 + , etc.) ± Microorganisms cooperate to make the transformation, each one providing their enzymatic capabilities and making use of the carbon source 15 © Arturo A. Kel er Biological Degradation ± Example of cooperative degradation: 16 © Arturo A. Kel er
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This note was uploaded on 08/06/2008 for the course ESM 222 taught by Professor Keller during the Spring '08 term at UCSB.

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Esm222_17_biodegrada - ESM 222 Biological Degradation Biodegradation involves the transformation of organic pollutants enzyme-catalyzed reactions

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