scholarly journals The Effect of Anaerobic Conditions on Two Heterotrich Ciliate Protozoa from Papyrus Swamps

1959 ◽  
Vol 36 (4) ◽  
pp. 583-589
Author(s):  
L. C. BEADLE ◽  
J. R. NILSSON
Keyword(s):  
Oxygen Concentration ◽  
Reduction Potential ◽  
Red Pigment ◽  
Low Oxygen ◽  
Anaerobic Conditions ◽  
Simultaneous Measurements ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Low Oxygen Concentration ◽  
Ciliate Protozoa

1. Under conditions of decreasing oxygen concentration in sealed bottles of swamp water Bursaria sp. always died as soon as the oxygen was exhausted, but Blepharisma undulans invariably survived 1-3 days of anaerobic conditions. 2. Simultaneous measurements of oxygen, pH and oxidation-reduction potential suggested that the oxygen concentration is the most important factor for survival. 3. The red pigment of B. undulans plays no part in the resistance to low oxygen concentration. 4. It is suggested as a hypothesis that B. undulans can live without oxygen until it has exhausted its reserves of carbohydrate, which can only be renewed in presence of oxygen.

Natural attenuation of chloroethenes: identification of sequential reductive/oxidative biodegradation by microcosm studies

2008 ◽  
Vol 58 (5) ◽  
pp. 1137-1145 ◽  
Author(s):  
K. R. Schmidt ◽  
A. Tiehm
Keyword(s):  
Reductive Dechlorination ◽  
Anaerobic Degradation ◽  
Reduction Potential ◽  
Oxidative Degradation ◽  
Contaminated Site ◽  
Low Oxygen ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Reductive Degradation ◽  
Microcosm Studies

A different lines of evidence approach for investigation of biodegradation processes at a chloroethene contaminated site showed well corresponding results of pollutant profiles, redox zonation, characterisation of autochthonic microflora and microcosm studies. In particular microcosm studies allowed identification of the predominating degradation pathways. Perchloroethene and trichloroethene are reductively chlorinated to mainly cis-1,2-dichloroethene (cDCE) under anaerobic conditions. Further reductive degradation to vinyl chloride (VC) is restricted to a distinct strongly anaerobic zone in the plume. Addition of high amounts of sediment material (80 vol%) to groundwater microcosms enabled reductive dechlorination without amendment with further auxiliary substrates. Reductive dechlorination was not irreversibly hindered by initially high nitrate concentrations and initially high oxidation–reduction potential. The products of anaerobic degradation cDCE and VC are subsequently aerobically mineralised, even when only low oxygen concentrations are available. Anaerobic oxidative degradation could not be proven in this study.

scholarly journals Analyzing changes in a leach solution oxygenation in the process of uranium ore borehole mining

2021 ◽  
Vol 15 (3) ◽  
pp. 39-44
Author(s):  
Erbolat Aben ◽  
Bakytzhan Toktaruly ◽  
Nursultan Khairullayev ◽  
Mukhtar Yeluzakh
Keyword(s):  
Sulfuric Acid ◽  
Flow Velocity ◽  
Oxygen Concentration ◽  
Acid Concentration ◽  
Reduction Potential ◽  
Sulfuric Acid Concentration ◽  
Leach Solution ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Solution Volume

Purpose is to increase uranium content in a PR solution while developing a technique varying oxidation-reduction potential of a leach solution with its oxygenation and identify changes in the oxygenation depending upon sulfuric acid concentration as well as transportation distance of the solution. Methods. A laboratory facility, involving solution tank, pump, Venturi tube, tank to install oxygen analyzer, and a dump tank, has been manufactured under the lab conditions to determine a leach solution oxygenation taking into consideration its delivery rate, sulfuric acid concentration, and temporal preservation of the concentration. Solution flow velocity; the deli-vered solution volume; sulfuric acid concentration; and distance from oxygenation point to a seam changed and varied during the study. Oxygenation was measured with the help of AZ 8403 oximeter; IT-1101 device was used to measure pH value as well as oxidation-reduction potential (ORP). Findings. A technique for a leach solution oxygenation and results of laboratory tests to identify influence of a sulfuric acid as well as transportation distance of a solution on oxygen concentration in the solution have been represented. It has been determined that Venturi tube helps oxygenize a leach solution; in this context, maximum oxygen concentration is achieved if a flow velocity is optimum one. It has been specified that a solution oxygenating depends upon a sulfuric acid concentration decreasing moderately with the increasing distance of the solution transportation. Originality.Following new dependencies have been determined: oxygen concentration in a solution upon a flow velocity and solution volume; and oxygen concentration in a solution upon distance from concentration place and sulfuric acid concentration. Practical implications.A leach solution oxygenation results in the increased oxidation-reduction potential and in the increased content of a useful component in the pregnant solution respectively. The proposed technique is notable for its low capital spending. Moreover, it is integrated easily into the available system being absolutely environmentally friendly.

PHYSIOLOGY OF SELENITE REDUCTION BY ENTEROCOCCI: I. INFLUENCE OF ENVIRONMENTAL VARIABLES

1967 ◽  
Vol 13 (9) ◽  
pp. 1175-1182 ◽  
Author(s):  
Richard C. Tilton ◽  
Haim B. Gunner ◽  
Warren Litsky
Keyword(s):  
Reduction Potential ◽  
Resting Cells ◽  
Anaerobic Conditions ◽  
Ph Optimum ◽  
Selenite Reduction ◽  
Factors Affecting ◽  
Maximum Reduction ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Intrinsic Capacity

Environmental factors affecting the reduction of selenite by growing and resting cells of Streptococcus faecalis N83 and Streptococcus faecium K6A, respectively, were studied. Both organisms displayed an intrinsic capacity to reduce selenite to the metallic selenium in a complex medium. However, concentrations of selenite above 50 μg/ml proved toxic to S. faecium, while S. faecalis tolerated and reduced selenite at concentrations as high as 1000 μg/ml. The pH optimum for selenite reduction lay between 7.2 and 7.7 for both organisms. Though maximum selenite reduction was shown by both under anaerobic conditions, S. faecalis, but not S. faecium, reduced selenite substantially even under aeration. The reduction of selenite by S. faecalis did not appear to be directly conditioned by the oxidation-reduction potential of the medium; a low potential was, however, necessary for the reduction of selenite by S. faecium. The presence of a flavin compound was associated with maximum reduction of selenite by S. faecalis, but effected no change in selenite reduction by S. faecium. The growth of these organisms could not be coupled to the reduction of selenite.

scholarly journals Influence of nitrite on the removal of Mn(II) using pilot-scale biofilters

2016 ◽  
Vol 7 (3) ◽  
pp. 264-271 ◽  
Author(s):  
Qingfeng Cheng ◽  
Lichao Nengzi ◽  
Dongying Xu ◽  
Junyuan Guo ◽  
Jing Yu
Keyword(s):  
Manganese Oxides ◽  
Reduction Potential ◽  
Ammonia Concentration ◽  
Pilot Scale ◽  
Gibbs Free Energy Change ◽  
Anaerobic Conditions ◽  
K Value ◽  
First Order ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

Two pilot-scale biofilters were used to systematically investigate the influence of nitrite on biological Mn(II) removal. Gibbs free energy change (ΔG) of the redox reaction between MnO2 and NO2– was 122.28 kJ mol–1 in 298 K, suggesting that MnO2 could not react with NO2–. When nitrite in the influent was increased from 0.05 to 0.5 mg L–1, manganese oxides did not react with nitrite in anaerobic conditions; nitrite was quickly oxidized and biological Mn(II) removal was slightly affected in 2 h in aerobic conditions. When nitrite was accumulated in the biofilter by increasing ammonia concentration, nitrite existed for more than 3 d and biological Mn(II) removal was affected in 3 d. When Mn(II) and ammonia in the influent were about 2 and 1.5 mg L–1, respectively, both of them were completely removed and the oxidation-reduction potential was increased with the depth of the filter from 16 to 122 mV. Biological Mn(II) removal followed the first-order reaction, and the k-value was 0.687 min–1.

Effect of low oxygen concentration on activation of inflammation by Helicobacter pylori

2021 ◽  
Vol 560 ◽  
pp. 179-185
Author(s):  
Adiza Abass ◽  
Tokuju Okano ◽  
Kotchakorn Boonyaleka ◽  
Ryo Kinoshita-Daitoku ◽  
Shoji Yamaoka ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Oxygen Concentration ◽  
Low Oxygen ◽  
Low Oxygen Concentration

scholarly journals In situ measurements of oxidation–reduction potential and hydrogen peroxide concentration as tools for revealing LPMO inactivation during enzymatic saccharification of cellulose

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Adnan Kadić ◽  
Anikó Várnai ◽  
Vincent G. H. Eijsink ◽  
Svein Jarle Horn ◽  
Gunnar Lidén
Keyword(s):  
Reduction Potential ◽  
Enzymatic Saccharification ◽  
The State ◽  
Enzyme Inactivation ◽  
Ex Situ ◽  
Process Economics ◽  
Complete Inactivation ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

Abstract Background Biochemical conversion of lignocellulosic biomass to simple sugars at commercial scale is hampered by the high cost of saccharifying enzymes. Lytic polysaccharide monooxygenases (LPMOs) may hold the key to overcome economic barriers. Recent studies have shown that controlled activation of LPMOs by a continuous H2O2 supply can boost saccharification yields, while overdosing H2O2 may lead to enzyme inactivation and reduce overall sugar yields. While following LPMO action by ex situ analysis of LPMO products confirms enzyme inactivation, currently no preventive measures are available to intervene before complete inactivation. Results Here, we carried out enzymatic saccharification of the model cellulose Avicel with an LPMO-containing enzyme preparation (Cellic CTec3) and H2O2 feed at 1 L bioreactor scale and followed the oxidation–reduction potential and H2O2 concentration in situ with corresponding electrode probes. The rate of oxidation of the reductant as well as the estimation of the amount of H2O2 consumed by LPMOs indicate that, in addition to oxidative depolymerization of cellulose, LPMOs consume H2O2 in a futile non-catalytic cycle, and that inactivation of LPMOs happens gradually and starts long before the accumulation of LPMO-generated oxidative products comes to a halt. Conclusion Our results indicate that, in this model system, the collapse of the LPMO-catalyzed reaction may be predicted by the rate of oxidation of the reductant, the accumulation of H2O2 in the reactor or, indirectly, by a clear increase in the oxidation–reduction potential. Being able to monitor the state of the LPMO activity in situ may help maximizing the benefit of LPMO action during saccharification. Overcoming enzyme inactivation could allow improving overall saccharification yields beyond the state of the art while lowering LPMO and, potentially, cellulase loads, both of which would have beneficial consequences on process economics.

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