Biomedical subjects

JN Petersen

Publications and source records attributed to JN Petersen.

3 recordsLinked to original sources

PubMed1999

Biotransformation of carbon tetrachloride by various acetate- and nitrate-limited denitrifying consortia

Fed-batch experiments were performed to determine the carbon tetrachloride (CT)-degrading ability of three denitrifying consortia cultured from sites not contaminated with CT. A mathematical model was used to quantify the rates of CT transformation by the consortia under both acetate-limiting and nitrate-limiting conditions. A rate constant for CT transformation on a cellular protein basis and the fraction of degraded CT transformed to chloroform (CF) were determined for each consortium by optimizing the model to fit the experimental data. The parameters for these experiments were statistically compared to those obtained for previous experiments with a denitrifying consortium cultured from an aquifer soil sample from the US Department of Energy Hanford site in southeastern Washington state. Results of F-test analysis indicated the rate of CT transformation and the production of CF both were functions of the limiting nutrient. Under nitrate-limited conditions, the rate constant for CT transformation for all four consortia was about 30 L/gmol/min and approximately 50% of the CT transformed was converted to CF. When acetate was the limiting nutrient, the rate constant for CT transformation was approximately 8 L/gmol/min and the CF yield decreased to about 25%. These results imply the ability to degrade CT may be inherent to some denitrifying organisms, regardless of previous exposure to CT. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗

PubMed1999

Selenium reduction by a denitrifying consortium.

A denitrifying bacterial consortium obtained from the Pullman, Washington wastewater treatment facility was enriched under denitrifying conditions and its ability to reduce selenite and selenate was studied. Replicate experiments at two different experimental conditions were performed. All experiments were performed under electron-acceptor limiting conditions, with acetate as the carbon source and nitrate the electron acceptor. In the first set of experiments, selenite was present, whereas, in the second set, selenate was added. A significant lag period of approximately 150 h was necessary before selenite or selenate reduction was observed. During this lag period, nitrate and nitrite use was observed. Once selenite or selenate reduction had started, nitrate and nitrite reduction was concomitant with selenium species reduction. Trace amounts of selenite were detected during the selenate reduction study. Analysis of the data indicates that, once selenium species reduction was induced, the rate of reduction was proportional to the selenium species concentration and to the biomass concentration. Furthermore, at similar biomass and contaminant concentrations, selenite reduction is approximately four times faster than selenate reduction. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗

PubMed1998

Biodegradation of 1,1,1-trichloroethane by a carbon tetrachloride-degrading denitrifying consortium

A denitrifying consortium capable of degrading carbon tetrachloride (CT) was shown to also degrade 1,1,1-trichloroethane (TCA). Fed-batch experiments demonstrated that the specific rate of TCA degradation by the consortium was comparable to the specific rate of CT degradation (approximately 0.01 L/gmol/min) and was independent of the limiting nutrient. Although previous work demonstrated that 4-50% of CT transformed by the consortium was converted to chloroform (CF), no reductive dechlorination products were detected during TCA degradation, regardless of the limiting nutrient. The lack of chlorinated TCA degradation products implies that the denitrifying consortium possesses an alternate pathway for the degradation of chlorinated solvents which does not involve reductive dechlorination. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗