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The role of redox mediators on the a...

Guerrero Barajas, Claudia.

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The role of redox mediators on the anaerobic degradation of chlorinated solvents.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	The role of redox mediators on the anaerobic degradation of chlorinated solvents./
作者:	Guerrero Barajas, Claudia.
面頁冊數:	212 p.
附註:	Source: Dissertation Abstracts International, Volume: 65-12, Section: B, page: 6582.
Contained By:	Dissertation Abstracts International65-12B.
標題:	Engineering, Environmental. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3158098
ISBN:	0496906313

The role of redox mediators on the anaerobic degradation of chlorinated solvents.
Guerrero Barajas, Claudia.

The role of redox mediators on the anaerobic degradation of chlorinated solvents. - 212 p.

Source: Dissertation Abstracts International, Volume: 65-12, Section: B, page: 6582.

Thesis (Ph.D.)--The University of Arizona, 2004.

Chlorinated solvents are pollutants found frequently in the environment. Whereas lower chlorinated solvents are easily degraded under aerobic conditions, degradation of higher chlorinated solvents is favored under anaerobic conditions. It is known that some compounds can act as redox mediators assisting the electron exchange required for the anaerobic dechlorination reactions to occur. Redox mediators are compounds that can assist the anaerobic dechlorination reactions either abiotically or biologically by accelerating the degradation rates. The objective of this study is to evaluate the role of different redox mediators on the anaerobic degradation of higher chlorinated solvents such as chloroform (CF), carbon tetrachloride (CT) and perchloroethylene (PCE). The redox mediators studied are vitamin B12 (cyanocobalamin CNB12-hydroxocobalamin HOB12), riboflavin (RF) and a model of humic compound anthraquinone-2,6-disulfonate (AQDS). The study includes abiotic and biological redox mediated dechlorination. The biological studies involve two varieties of unadapted methanogenic sludge. The results obtained demonstrate that redox mediators greatly enhance the degradation rates of CF and CT when utilized at substoichiometric molar ratios. At the same time, the results also highlight the importance of the role of the microorganisms during the dechlorination process. Vitamin B12 and riboflavin presented larger impact than AQDS on the degradation rates of CF and CT. Since vitamin B12 had the highest positive impact on the biodegradation rates of CF and CT, an attempt was done to stimulate its biosynthesis by the methanogenic sludge during the CT dechlorination. The approach used to promote the biosynthesis of vitamin B12 involved different vitamin B12 precursors such as porphobilinogen, and some primary substrates such as methanol and 1,2-propanediol. The results obtained show that the formation of the corrin ring may be the limiting step during vitamin B12 biosynthesis. One carbon substrates such as methanol, combined with porphobilinogen had a positive impact on the biodegradation rates of CT. The study suggests that the combination of methanol and vitamin B12 precursors could be a good alternative to stimulate the vitamin B12 biosynthesis by methanogens and therefore, the enhancement of the biodegradation rates of chlorinated solvents.

ISBN: 0496906313Subjects--Topical Terms:

783782
Engineering, Environmental.

The role of redox mediators on the anaerobic degradation of chlorinated solvents.
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502 $a Thesis (Ph.D.)--The University of Arizona, 2004.
520 $a Chlorinated solvents are pollutants found frequently in the environment. Whereas lower chlorinated solvents are easily degraded under aerobic conditions, degradation of higher chlorinated solvents is favored under anaerobic conditions. It is known that some compounds can act as redox mediators assisting the electron exchange required for the anaerobic dechlorination reactions to occur. Redox mediators are compounds that can assist the anaerobic dechlorination reactions either abiotically or biologically by accelerating the degradation rates. The objective of this study is to evaluate the role of different redox mediators on the anaerobic degradation of higher chlorinated solvents such as chloroform (CF), carbon tetrachloride (CT) and perchloroethylene (PCE). The redox mediators studied are vitamin B12 (cyanocobalamin CNB12-hydroxocobalamin HOB12), riboflavin (RF) and a model of humic compound anthraquinone-2,6-disulfonate (AQDS). The study includes abiotic and biological redox mediated dechlorination. The biological studies involve two varieties of unadapted methanogenic sludge. The results obtained demonstrate that redox mediators greatly enhance the degradation rates of CF and CT when utilized at substoichiometric molar ratios. At the same time, the results also highlight the importance of the role of the microorganisms during the dechlorination process. Vitamin B12 and riboflavin presented larger impact than AQDS on the degradation rates of CF and CT. Since vitamin B12 had the highest positive impact on the biodegradation rates of CF and CT, an attempt was done to stimulate its biosynthesis by the methanogenic sludge during the CT dechlorination. The approach used to promote the biosynthesis of vitamin B12 involved different vitamin B12 precursors such as porphobilinogen, and some primary substrates such as methanol and 1,2-propanediol. The results obtained show that the formation of the corrin ring may be the limiting step during vitamin B12 biosynthesis. One carbon substrates such as methanol, combined with porphobilinogen had a positive impact on the biodegradation rates of CT. The study suggests that the combination of methanol and vitamin B12 precursors could be a good alternative to stimulate the vitamin B12 biosynthesis by methanogens and therefore, the enhancement of the biodegradation rates of chlorinated solvents.
520 $a This study presents the lowest molar ratio of vitamins that enhanced the dechlorination rates reported so far for biodegradation of chlorinated solvents involving methanogens. Also, this is the first report on the use of riboflavin as a redox mediator during dechlorination processes.
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