Inhibitory effects of nitrate reduction on methanogenesis in the presence of different electron donors

2008 ◽  
Vol 57 (5) ◽  
pp. 693-698 ◽  
Author(s):  
A. E. Tugtas ◽  
S. G. Pavlostathis
Keyword(s):  
Methane Production ◽  
Nitrate Reduction ◽  
Nitrate Concentration ◽  
Electron Donors ◽  
Inhibitory Effects ◽  
Preferential Utilization

The preferential utilization of different electron donors and their effects on the nitrate reduction and methanogenesis in a mixed, mesophilic (35°C) methanogenic culture were investigated. Batch methanogenic cultures were fed with dextrin/peptone (D/P), propionate, acetate, and H2/CO2 at an initial COD of 500 mg/L and an initial nitrate concentration of 50 mg N/L. Immediate cessation of methane production was observed in all nitrate-amended cultures. Methane production completely recovered in the D/P- and acetate-fed cultures, and partially recovered or did not recover in the propionate- and H2/CO2-fed, nitrate-amended cultures, respectively. Accumulation of denitrification intermediates was observed in both the propionate- and H2/CO2-fed cultures, which resulted in inhibition of fermentation and/or methanogenesis. The fastest and the slowest nitrate reduction were observed in the acetate- and propionate-fed cultures, respectively.

Studies on the Mechanism of NAD-photoreduction by Chromatophores of the Facultative Phototroph, Rhodopseudomonas capsulata

1969 ◽  
Vol 24 (1) ◽  
pp. 67-76 ◽  
Author(s):  
J.-H. Klemme
Keyword(s):  
Nicotinamide Adenine Dinucleotide ◽  
Molecular Hydrogen ◽  
Reaction System ◽  
Electron Donors ◽  
Rhodopseudomonas Capsulata ◽  
Antimycin A ◽  
Inhibitory Effects ◽  
Carbonyl Cyanide ◽  
Cyclic Photophosphorylation ◽  
Energy Dependent

The light-driven and the ATP-driven reduction of nicotinamide adenine dinucleotide (NAD) catalyzed by the chromatophore fraction of Rhodopseudomonas capsulata was investigated. Efficient electron donors for the photoreduction of NAD are molecular hydrogen and succinate. In the ATP-dependent reaction system, succinate is a more efficient electron donor than H2. The energydependent NAD-reduction is driven by ATP, but not by pyrophosphate or ADP. Oligomycin stimulates the NAD-photoreductions and completely inhibits the ATP-driven NAD-reductions. Rotenone and piericidin A are inhibitors for both the light-driven and the ATP-driven NAD-reductions. Antimycin A is an inhibitor only for the light-driven reductions. The H2-linked NAD-photoreduction is less sensitive to these inhibitors and to the uncoupler desaspidin than the succinate-linked reduction. Atebrine, carbonyl cyanide-m-chlorophenylhydrazone, 2,4-dinitrophenol and phenazonium methosulfate are inhibitors for the light-driven and the ATP-driven reductions. Some of the compounds used as inhibitors of the NAD-reduction were also investigated with concerns to their inhibitory effects on cyclic photophosphorylation and O2-linked oxidations of reduced NAD, succinate and H2. Based on the results of these inhibitor studies, the relationships between cyclic photophosphorylation, light-induced noncyclic electron transport and energy-dependent NAD-reduction are discussed.

scholarly journals Anaerobic Degradation of Benzene, Toluene, Ethylbenzene, and Xylene Compounds by Dechloromonas Strain RCB

2005 ◽  
Vol 71 (12) ◽  
pp. 8649-8655 ◽  
Author(s):  
Romy Chakraborty ◽  
Susan M. O'Connor ◽  
Emily Chan ◽  
John D. Coates
Keyword(s):  
Electron Acceptor ◽  
Nitrate Reduction ◽  
Anaerobic Degradation ◽  
Electron Donors ◽  
Metabolic Versatility ◽  
Potential Applicability ◽  
Benzene Toluene ◽  
Total Hydrocarbons ◽  
Unidentified Metabolite

ABSTRACT Dechloromonas strain RCB has been shown to be capable of anaerobic degradation of benzene coupled to nitrate reduction. As a continuation of these studies, the metabolic versatility and hydrocarbon biodegradative capability of this organism were investigated. The results of these revealed that in addition to nitrate, strain RCB could alternatively degrade benzene both aerobically and anaerobically with perchlorate or chlorate [(per)chlorate] as a suitable electron acceptor. Furthermore, with nitrate as the electron acceptor, strain RCB could also utilize toluene, ethylbenzene, and all three isomers of xylene (ortho-, meta-, and para-) as electron donors. While toluene and ethylbenzene were completely mineralized to CO2, strain RCB did not completely mineralize para-xylene but rather transformed it to some as-yet-unidentified metabolite. Interestingly, with nitrate as the electron acceptor, strain RCB degraded benzene and toluene concurrently when the hydrocarbons were added as a mixture and almost 92 μM total hydrocarbons were oxidized within 15 days. The results of these studies emphasize the unique metabolic versatility of this organism, highlighting its potential applicability to bioremediative technologies.

scholarly journals Peatland types influence the inhibitory effects of a humic substance analog on methane production

Geoderma ◽  
2016 ◽  
Vol 265 ◽  
pp. 131-140 ◽  
Author(s):  
Rongzhong Ye ◽  
Jason K. Keller ◽  
Qusheng Jin ◽  
Brendan J.M. Bohannan ◽  
Scott D. Bridgham
Keyword(s):  
Humic Substance ◽  
Methane Production ◽  
Inhibitory Effects

scholarly journals Enhancement of methane production from 1-hexadecene by additional electron donors

2017 ◽  
Vol 11 (4) ◽  
pp. 657-666 ◽  
Author(s):  
A. M. S. Paulo ◽  
A. F. Salvador ◽  
J. I. Alves ◽  
R. Castro ◽  
A. A. M. Langenhoff ◽  
...  
Keyword(s):  
Methane Production ◽  
Electron Donors

Fate of Neptunium in an Anaerobic, Ethanogenic Microcosm

1999 ◽  
Vol 556 ◽  
Author(s):  
J. E. Banaszak ◽  
S. M. Webb ◽  
B. E. Rittmann ◽  
J.-F. Gaillard ◽  
D. T. Reed
Keyword(s):  
Methane Production ◽  
Analytical Techniques ◽  
Electron Donors ◽  
Natural Systems ◽  
Sulfate Reducing ◽  
Exogenous Substrate ◽  
Nir Absorption ◽  
Abiotic Controls ◽  
Control Samples ◽  
Substrate Addition

AbstractNeptunium is found predominantly as Np(IV) in reducing environments, but as Np(V) in aerobic environments. Currently, it is not known how the interplay between biotic and abiotic processes affects Np redox speciation in the environment. To evaluate the effect of anaerobic microbial activity on the fate of Np in natural systems, Np(V) was added to a microcosm inoculated with anaerobic sediments from a metal-contaminated freshwater lake. The consortium included metal-reducing, sulfate-reducing, and methanogenic microorganisms, and acetate was supplied as the only exogenous substrate. Addition of more than 10−5M Np did not inhibit methane production. Total Np solubility in the active microcosm, as well as in sterilized control samples, decreased by nearly two orders of magnitude. A combination of analytical techniques, including VIS-NIR absorption spectroscopy and XANES, identified Np(IV) as the oxidation state associated with the sediments. The similar results from the active microcosm and the abiotic controls suggest that microbially produced Mn(II/III) and Fe(II) may serve as electron donors for Np reduction.

Inhibitory effects of long-chain fatty acids on VFA degradation and β-oxidation

2003 ◽  
Vol 47 (10) ◽  
pp. 139-146 ◽  
Author(s):  
H.-S. Shin ◽  
S.-H. Kim ◽  
C.-Y. Lee ◽  
S.-Y. Nam
Keyword(s):  
Fatty Acids ◽  
Methane Production ◽  
Substrate Inhibition ◽  
Long Chain Fatty Acids ◽  
Inhibitory Effects ◽  
Inhibition Model ◽  
Propionate Degradation ◽  
Acetate Degradation ◽  
Long Chain ◽  
Chain Fatty Acids

The inhibitory effects of major long-chain fatty acids (LCFA), which have 16 or 18 carbons, not only on acetate degradation, but also on propionate degradation and β-oxidation were examined in anaerobic serum bottle tests at 35°C with the acclimated granular sludges. A modified Gompertz equation described cumulative methane production to assess the rates of VFA degradation and β-oxidation, which were applied to a simplified noncompetitive model and a simplified substrate inhibition model, respectively. The specific methane production rates on acetate decreased as LCFA concentration increased, which was in good agreement with the noncompetitive inhibition model. Unsaturated oleate (C18:1) and linoleate (C18:2) were more inhibitory than saturated stearate (C18:0) and palmitate (C16:0) on acetate degradation. LCFA inhibition on propionate degradation was similar to that for acetate; however, propionate degradation was less inhibited than acetate degradation. β-oxidation was the rate-limiting step in LCFA degradation in most cases. As LCFA concentration increased, β-oxidation rate reached the maximum value, and then decreased, which confirmed the substrate inhibition of LCFA. Oleate, the most abundant LCFA in wastewater, could be degraded more quickly than saturated LCFA containing the same or even less carbon in spite of relatively high toxicity on acetate degradation.

POLYPYRROLE COATED CELLULOSIC SUBSTRATE MODIFIED BY COPPER OXIDE AS ELECTRODE FOR NITRATE ELECTROREDUCTION

2015 ◽  
Vol 22 (05) ◽  
pp. 1550065 ◽  
Author(s):  
A. HAMAM ◽  
D. OUKIL ◽  
A. DIB ◽  
H. HAMMACHE ◽  
L. MAKHLOUFI ◽  
...  
Keyword(s):  
Copper Oxide ◽  
Nitrate Reduction ◽  
Electrochemical Impedance ◽  
Nitrate Concentration ◽  
Film Surface ◽  
Xrd Analysis ◽  
Electrochemical Reactivity ◽  
Cellulosic Substrate ◽  
Oxide Particles ◽  
Cyclic Voltamperometry

The aim of this work is to synthesize polypyrrole (PPy) films on nonconducting cellulosic substrate and modified by copper oxide particles for use in the nitrate electroreduction process. Firstly, the chemical polymerization of polypyrrole onto cellulosic substrate is conducted by using FeCl 3 as an oxidant and pyrrole as monomer. The thickness and topography of the different PPy films obtained were estimated using a profilometer apparatus. The electrochemical reactivity of the obtained electrodes was tested by voltamperometry technique and electrochemical impedance spectroscopy. Secondly, the modification of the PPy film surface by incorporation of copper oxide particles is conducted by applying a galvanostatic procedure from a CuCl 2 solution. The SEM, EDX and XRD analysis showed the presence of CuO particles in the polymer films with dimensions less than 50 nm. From cyclic voltamperometry experiments, the composite activity for the nitrate electroreduction reaction was evaluated and the peak of nitrate reduction is found to vary linearly with initial nitrate concentration.

Methanogenic potential of tailings samples from oil sands extraction plants

2002 ◽  
Vol 48 (1) ◽  
pp. 21-33 ◽  
Author(s):  
Phillip M Fedorak ◽  
Debora L Coy ◽  
Myrna J Salloum ◽  
Marvin J Dudas
Keyword(s):  
Methane Production ◽  
Oil Sands ◽  
Sulfate Reducing Bacteria ◽  
Extraction Process ◽  
Hot Water ◽  
Electron Donors ◽  
Sulfate Reducing ◽  
Settling Ponds ◽  
Reducing Bacteria ◽  
Composite Tailings

Approximately 20% of Canada's oil supply now comes from the extraction of bitumen from the oil sands deposits in northeastern Alberta. The oil sands are strip-mined, and the bitumen is typically separated from sand and clays by an alkaline hot water extraction process. The rapidly expanding oil sands industry has millions of cubic metres of tailings for disposal and large areas of land to reclaim. There are estimates that the consolidation of the mature fine tails (MFT) in the settling ponds will take about 150 years. Some of the settling ponds are now evolving microbially produced methane, a greenhouse gas. To hasten consolidation, gypsum (CaSO4·2H2O) is added to MFT, yielding materials called consolidated or composite tailings (CT). Sulfate from the gypsum has the potential to stimulate sulfate-reducing bacteria (SRB) to out-compete methanogens, thereby stopping methanogenesis. This investigation examined three MFT and four CT samples from three oil sands extractions companies. Each was found to contain methanogens and SRB. Serum bottle microcosm studies showed sulfate in the CT samples stopped methane production. However, if the microcosms were amended with readily utilizable electron donors, the sulfate was consumed, and when it reached approximately 20 mg/L, methane production began. Some unamended microcosms were incubated for 372 days, with no methane production detected. This work showed that each MFT and CT sample has the potential to become methanogenic, but in the absence of exogenous electron donors, the added sulfate can inhibit methanogenesis for a long time.Key words: consolidated tailings, composite tailings, methanogens, oil sands, sulfate-reducing bacteria.

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