title: Electron donor effect on nitrate reduction pathway and kinetics in a mixed methanogenic culture.
abstract: The effect of different electron donors on the pathway and kinetics of nitrate reduction in a sulfide-acclimated mixed, mesophilic (35 degrees C) methanogenic culture was investigated. A mixture of dextrin and peptone, glucose, propionate, acetate, and H(2)/CO(2) were used as substrates at an initial chemical oxygen demand of 1,500 mg/L and the initial nitrate concentration ranged between 0 and 300 mg N/L. The fastest nitrate reduction was observed in the H(2)/CO(2) and acetate-fed cultures. In the case of propionate, nitrate reduction was the slowest followed by partial recovery of methanogenesis and accumulation of volatile fatty acids due to inhibition as a result of accumulation of denitrification intermediates. Similarly, accumulation of nitrite and nitric oxide and partial or complete inhibition of methanogenesis was observed in the H(2)/CO(2)-fed cultures. Methanogenesis completely recovered in the dextrin/peptone-, glucose-, and acetate-fed cultures at all nitrate levels. Denitrification was the dominant pathway of nitrate reduction in the propionate-, acetate-, and H(2)/CO(2)-fed cultures regardless of the COD/N value. However, both denitrification and dissimilatory nitrate reduction to ammonia (DNRA) were observed in the dextrin/peptone- and glucose-fed cultures and the degree of predominance of either of the two pathways was a function of the COD/N value. Therefore, the type of electron donor used affected both the nitrate reduction pathway and kinetics, as well as the recovery of fermentation and/or methanogenesis in the mixed methanogenic culture.
authors.affiliation: School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, Georgia 30332-0512, USA.
authors.forename: A Evren
authors.initials: AE
authors.lastname: Tugtas
authors.forename: Spyros G
authors.initials: SG
authors.lastname: Pavlostathis
mesh_terms: D001421:Bacteria, Anaerobic / Q000378:metabolism*; D003198:Computer Simulation; D004579:Electron Transport; D007700:Kinetics; D008697:Methane / Q000378:metabolism*; D008954:Models, Biological; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction; D012722:Sewage / Q000382:microbiology*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D009566:Nitrates; D012722:Sewage; D008697:Methane