scholarly journals Relationship of Hydrogen Bioavailability to Chromate Reduction in Aquifer Sediments

2001 ◽  
Vol 67 (4) ◽  
pp. 1517-1521 ◽  
Author(s):  
Tamara L. Marsh ◽  
Michael J. McInerney
Keyword(s):  
Hydrogen Concentration ◽  
Detection Limits ◽  
Mercury Vapor ◽  
Electron Donors ◽  
Chromate Reduction ◽  
No Donor ◽  
Reducing Conditions ◽  
Dissolved Hydrogen ◽  
Endogenous Substrates ◽  
Relationship Of

ABSTRACT Biological Cr(VI) reduction was studied in anaerobic sediments from an aquifer in Norman, Okla. Microcosms containing sediment and mineral medium were amended with various electron donors to determine those most important for biological Cr(VI) reduction. Cr(VI) (about 340 μM) was reduced with endogenous substrates (no donor), or acetate was added. The addition of formate, hydrogen, and glucose stimulated Cr(VI) reduction compared with reduction in unamended controls. From these sediments, an anaerobic Cr(VI)-utilizing enrichment was obtained that was dependent upon hydrogen for both growth and Cr(VI) reduction. No methane was produced by the enrichment, which reduced about 750 μM Cr(VI) in less than six days. The dissolved hydrogen concentration was used as an indicator of the terminal electron accepting process occurring in the sediments. Microcosms with sediments, groundwater, and chromate metabolized hydrogen to a concentration below the detection limits of the mercury vapor gas chromatograph. In microcosms without chromate, the hydrogen concentration was about 8 nM, a concentration comparable to that under methanogenic conditions. When these microcosms were amended with 500 μM Cr(VI), the dissolved hydrogen concentration quickly fell below the detection limits. These results showed that the hydrogen concentration under chromate-reducing conditions became very low, as low as that reported under nitrate- and manganese-reducing conditions, a result consistent with the free energy changes for these reactions. The utilization of formate, lactate, hydrogen, and glucose as electron donors for Cr(VI) reduction indicates that increasing the availability of hydrogen results in a greater capacity for Cr(VI) reduction. This conclusion is supported by the existence of an enrichment dependent upon hydrogen for growth and Cr(VI) reduction.

scholarly journals Case Study of Anaerobic Digestion Process Stability Detected by Dissolved Hydrogen Concentration

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 106
Author(s):  
Daniela Platošová ◽  
Jiří Rusín ◽  
Jan Platoš ◽  
Kateřina Smutná ◽  
Roman Buryjan
Keyword(s):  
Anaerobic Digestion ◽  
Correlation Coefficient ◽  
Hydrogen Concentration ◽  
Pearson’S Correlation ◽  
Pearson’S Correlation Coefficient ◽  
Digestion Process ◽  
Short Service Life ◽  
Pearson's Correlation ◽  
Dissolved Hydrogen ◽  
Pearson's Correlation Coefficient

The paper presents the results of a laboratory experiment of mesophilic single-stage anaerobic digestion performed to verify the possibility of early detection of process instability and reactor overload by evaluating the course of dissolved hydrogen concentration of the main intermediate. The digestion process was run in a Terrafors IS rotary drum bioreactor for 230 days. The substrate dosed on weekdays was food leftovers from the university canteen. At an average temperature of 37 °C, an organic loading of volatiles of 0.858 kg m−3 day−1 and a theoretical retention time of 259 days, biogas production of 0.617 Nm3 kg VS−1 was achieved with a CH4 content of 51.7 vol. %. The values of the established FOS/TAC stability indicator ranged from 0.26 to 11.4. The highest value was reached when the reactor was overloaded. The dissolved hydrogen concentration measured by the amperometric microsensor ranged from 0.039–0.425 mg dm−3. Data were statistically processed using Pearson’s correlation coefficient. The correlation of the hydrogen concentration with other parameters such as the concentration of organic acids was evaluated. The value of Pearson’s correlation coefficient was 0.331 and corresponded to a p-value of 0. The results confirmed a very low limit of the hydrogen concentration at which the microbial culture, especially methanogens, was already overloaded. The amperometric microsensor proved to be rather unsuitable for operational applications due to insufficient sensitivity and short service life. The newly designed ratio of dissolved hydrogen concentration to neutralizing capacity was tested but did not work significantly better than the established FOS/TAC stability indicator.

scholarly journals Ubiquinone reduction pattern in pigeon heart mitochondria. Identification of three distinct ubiquinone pools

1985 ◽  
Vol 229 (3) ◽  
pp. 621-629 ◽  
Author(s):  
B M Jørgensen ◽  
H N Rasmussen ◽  
U F Rasmussen
Keyword(s):  
Citric Acid ◽  
Citric Acid Cycle ◽  
Nadh Oxidase ◽  
Heart Mitochondria ◽  
Acid Cycle ◽  
Oxidase System ◽  
Mitochondrial Inner Membrane ◽  
Reducing Conditions ◽  
Endogenous Substrates ◽  
Effect Of Inhibitors

Intact pigeon heart mitochondria showed 10-30% ubiquinone reduction in the absence of substrates. This reduction could not be ascribed to endogenous substrates, as judged by lack of effect of inhibitors and uncouplers and by the very low endogenous respiratory rate. Addition of NADH in the presence of antimycin caused further reduction of about 10% ubiquinone, apparently coupled to the rotenone- and antimycin-sensitive exo-NADH oxidase system [Rasmussen (1969) FEBS Lett. 2, 157-162]. Citric acid cycle substrates reduced most of the remaining ubiquinone in the presence of antimycin; 15-20% of the total ubiquinone content was still in the oxidized form under the most reducing conditions. Three pools of ubiquinone therefore appeared to be present in heart mitochondria: a metabolically inactive pool consisting of reduced as well as oxidized ubiquinone, a pool coupled to oxidation of added (cytoplasmic) NADH, and the well-known pool coupled to citric acid cycle oxidations. Ferricyanide selectively oxidized the ubiquinol reduced by added NADH, indicating that this pool is situated on the outer surface of the mitochondrial inner membrane. Ubiquinone reduction levels were determined with a new method, which is described in detail.

scholarly journals Impact of Organic Carbon Electron Donors on Microbial Community Development under Iron- and Sulfate-Reducing Conditions

PLoS ONE ◽  
2016 ◽  
Vol 11 (1) ◽  
pp. e0146689 ◽  
Author(s):  
Man Jae Kwon ◽  
Edward J. O’Loughlin ◽  
Maxim I. Boyanov ◽  
Jennifer M. Brulc ◽  
Eric R. Johnston ◽  
...  
Keyword(s):  
Microbial Community ◽  
Organic Carbon ◽  
Community Development ◽  
Electron Donors ◽  
Sulfate Reducing ◽  
Reducing Conditions

scholarly journals Conversion of p-coumarate into caffeate by Streptomyces nigrifaciens. Purification and properties of the hydroxylating enzyme

1972 ◽  
Vol 130 (2) ◽  
pp. 425-433 ◽  
Author(s):  
A. M. D. Nambudiri ◽  
J. V. Bhat ◽  
P. V. Subba Rao
Keyword(s):  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Gel Filtration ◽  
Thiol Group ◽  
Electron Donors ◽  
Copper Protein ◽  
Purification And Properties ◽  
Relationship Of ◽  
The Relationship ◽  
Mediated Catalysis

1. An enzyme responsible for the conversion of p-coumarate into caffeate was purified 97-fold from Streptomyces nigrifaciens. The enzyme had a molecular weight of 18000 as determined by Sephadex G-100 gel filtration and was homogeneous on polyacrylamide-gel electrophoresis. 2. The preparation exhibited both p-coumarate hydroxylase and caffeate oxidase activities. 3. Stoicheiometry of the reaction indicated a mono-oxygenase-mediated catalysis consuming 1mol of O2/mol of substrate hydroxylated. 4. NADH, NADPH, tetrahydropteroylglutamate or ascorbate act as electron donors for the reaction, ascorbate being inhibitory at higher concentrations. 5. The optimum enzyme activity was at about pH7.7 and 40°C, with an activation energy of 39kJ/mol. 6. Monophenols such as p-hydroxyphenylpropionate, p-hydroxyphenylacetate, l-tyrosine and dl-p-hydroxyphenyl-lactate were also hydroxylated by the preparation, in addition to p-coumarate. 7. The enzyme was a copper protein having 0.38% copper in a bound form. 8. Thiol-group inhibitors did not affect the reaction. 9. The relationship of the enzyme to other hydroxylases is discussed.

Effects of Dissolved Hydrogen on Crack Growth Rate of Warm-Rolled 316L Austenitic Stainless Steel in Primary Water Condition

2015 ◽  
Author(s):  
Kyoung Joon Choi ◽  
Seung Chang Yoo ◽  
Taeho Kim ◽  
Seong Sik Hwang ◽  
Min Jae Choi ◽  
...  
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Hydrogen Concentration ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Condition ◽  
Primary Water ◽  
Dissolved Hydrogen

With the extension of pressurized water reactor’s design life or continued operation, more careful study on the integrity of the internal structures needs to be pursued. In this study, warm-rolling and heat-treatment were applied to 316L stainless steel, in order to simulate the effect of radiation damage such as hardening and radiation-induced grain boundary segregation. And, the crack growth rate testing under constant load condition was performed in the primary water conditions of a pressurized water reactor. Also, in order to investigate the effect of dissolved hydrogen on the crack growth, the dissolved hydrogen concentration was varied between 30 to 50 cc/kg in simulated primary water condition of a pressurized water reactor. The warm-rolled specimens showed the higher crack growth rate than as-received one. Also, the crack growth rate increased as the dissolved hydrogen concentration increases.

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