scholarly journals Photosynthesis under very high oxygen concentrations in dense microbial mats and biofilms

2018 ◽  
Author(s):  
Dirk de Beer ◽  
Volker Meyer ◽  
Judith Klatt ◽  
Tong Li
Keyword(s):  
Microbial Mats ◽  
Removal Rate ◽  
Bubble Formation ◽  
Water Volume ◽  
Energy Costs ◽  
Light Conditions ◽  
Gas Formation ◽  
High Concentrations ◽  
Kinetics Of ◽  
Very High

AbstractUsing microsensors O2concentrations were measured in photosynthetically active microbial mats of up to 3 mM, corresponding to a partial pressure of 3 bar. This could damage mats by internal gas formation, and be inhibitory by formation of reactive oxygen species (ROS) and reduced effectivity of RuBisCo. The reliability of the electrochemical microsensors was checked by creating elevated O2concentrations in a water volume placed inside a pressure tank. A microsensor mounted with the tip in the gassed water bath showed a response linearly proportional to 5.5 mM corresponding to 4 bar pure O2pressure. After release of the pressure the O2concentration reduced quickly to 2.5 mM, then stabilized and subsequently reduced slowly over 14 hours to approximately 2 mM. We concluded that the very high O2concentrations measured in phototrophic microbial mats are real and O2oversaturation in mats is a stable phenomenon. As consequence of high O2concentrations, net production of H2O2occurred. The accumulation was, however, limited to the respiratory zone under the photosynthetic layer. Despite the high gas pressure inside mats, no disruption of the mat structure was apparent by bubble formation inside the mats,and bubbles were only observed at mat surfaces. Additions of H2O2to high concentrations in the water column were efficiently removed in the photosynthetically active zone. As the removal rate was linearly proportional to the H2O2influx, this removal occurred possibly not enzymatically but by abiotic processes. Phototrophic microorganisms can produce O2at high rates under strongly elevated O2levels, despite the decreased efficiency due to the unfavorable kinetics of RuBisCo and energy costs for protection. Under non-limiting light conditions, this apparent dilemma is, however, not disadvantageous.ImportanceBiofilms are often used in photobioreactors for production of biomass, food or specialty chemistry. Photosynthesis rates can be limited by high O2levels or high O2/CO2ratios which are especially enhanced in biofilms and mats, due to mass transfer limitations. High O2may lead to reactive O2species (ROS) and reduce the efficiency of RuBisCo. Moreover, gas formation may destabilize their structure. Here we show that extremely high levels of O2are possible in mats and biofilms without ebullition, and while maintaining very high photosynthetic activity.

Improved Patient Safety Due to Catheter-Based Gas Bubble Removal During TURBT

2020 ◽  
Vol 9 (2) ◽  
pp. 1-11
Author(s):  
Holger Fritzsche ◽  
Elmer Jeto Gomes Ataide ◽  
Axel Boese ◽  
Michael Friebe
Keyword(s):  
Patient Safety ◽  
Irrigation System ◽  
Removal Rate ◽  
Bubble Formation ◽  
Technical Solution ◽  
Air Bubbles ◽  
Gas Bubble ◽  
Suction System ◽  
Gas Formation ◽  
Controlled Irrigation

TURBT (transurethral resection of bladder tumor) is a standard treatment for bladder cancer. Gas bubble formation is caused by the heating of the RF-electrode from the resectoscope, which causes visual impairments and can also lead to explosive gas formation. The purpose of this work is to find a proper technical solution for removing the air bubbles and toxic gases during electro-resection thereby providing patient safety as well as better operating comfort for surgeons. A continuously controlled irrigation system and catheter based simultaneous suction system was designed, implemented and tested, with an average removal rate of 70% of the air bubbles and gases that appeared inside the urinary bladder. The setup was tested using a dedicated phantom.

scholarly journals Hexokinase Regulates Kinetics of Glucose Transport and Expression of Genes Encoding Hexose Transporters inSaccharomyces cerevisiae

2000 ◽  
Vol 182 (23) ◽  
pp. 6815-6818 ◽  
Author(s):  
Thomas Petit ◽  
Jasper A. Diderich ◽  
Arthur L. Kruckeberg ◽  
Carlos Gancedo ◽  
Karel Van Dam
Keyword(s):  
Glucose Transport ◽  
Mrna Levels ◽  
High Affinity ◽  
Expression Of Genes ◽  
Hexose Transporters ◽  
Genes Encoding ◽  
High Concentrations ◽  
Kinetics Of ◽  
Very High ◽  
Null Strain

ABSTRACT Glucose transport kinetics and mRNA levels of different glucose transporters were determined in Saccharomyces cerevisiaestrains expressing different sugar kinases. During exponential growth on glucose, a hxk2 null strain exhibited high-affinity hexose transport associated with an elevated transcription of the genesHXT2 and HXT7, encoding high-affinity transporters, and a diminished expression of the HXT1 andHXT3 genes, encoding low-affinity transporters. Deletion ofHXT7 revealed that the high-affinity component is mostly due to HXT7; however, a previously unidentified very-high-affinity component (Km = 0.19 mM) appeared to be due to other factors. Expression of genes encoding hexokinases from Schizosaccharomyces pombe orYarrowia lipolytica in a hxk1 hxk2 glk1 strain prevented derepression of the high-affinity transport system at high concentrations of glucose.

scholarly journals Some properties of pyruvate and 2-oxoglutarate oxidation by blowfly flight-muscle mitochondria

1972 ◽  
Vol 127 (1) ◽  
pp. 271-283 ◽  
Author(s):  
R. G. Hansford
Keyword(s):  
Oxygen Uptake ◽  
Isocitrate Dehydrogenase ◽  
Adenine Nucleotides ◽  
Slight Reduction ◽  
Glycerol Phosphate ◽  
Pyruvate Oxidation ◽  
Low Concentrations ◽  
High Concentrations ◽  
Kinetics Of ◽  
Very High

1. High rates of state 3 pyruvate oxidation are dependent on high concentrations of inorganic phosphate and a predominance of ADP in the intramitochondrial pool of adenine nucleotides. The latter requirement is most marked at alkaline pH values, where ATP is profoundly inhibitory. 2. Addition of CaCl2 during state 4, state 3 (Chance & Williams, 1955) or uncoupled pyruvate oxidation causes a marked inhibition in the rate of oxygen uptake when low concentrations of mitochondria are employed, but may lead to an enhancement of state 4 oxygen uptake when very high concentrations of mitochondria are used. 3. These properties are consistent with the kinetics of the NAD-linked isocitrate dehydrogenase (EC 1.1.1.41) from this tissue, which is activated by isocitrate, citrate, ADP, phosphate and H+ ions, and inhibited by ATP, NADH and Ca2+. 4. Studies of the redox state of NAD and cytochrome c show that addition of ADP during pyruvate oxidation causes a slight reduction, whereas addition during glycerol phosphate oxidation causes a `classical' oxidation. Nevertheless, it is concluded that pyruvate oxidation is probably limited by the respiratory chain in state 4 and by the NAD-linked isocitrate dehydrogenase in state 3. 5. The oxidation of 2-oxoglutarate by swollen mitochondria is also stimulated by high concentrations of ADP and phosphate, and is not uncoupled by arsenate.

Quantitative and qualitative hydrologic balance for a suburban watershed with a separate sewer system (Nantes, France)

2005 ◽  
Vol 51 (2) ◽  
pp. 231-238 ◽  
Author(s):  
V. Ruban ◽  
F. Larrarte ◽  
M. Berthier ◽  
L. Favreau ◽  
Y. Sauvourel ◽  
...  
Keyword(s):  
Waste Water ◽  
Water System ◽  
Storm Water ◽  
Water Volume ◽  
Water Runoff ◽  
Sewer System ◽  
Qualitative And Quantitative ◽  
Storm Water Runoff ◽  
High Concentrations ◽  
Very High

A qualitative and quantitative budget at the outlet of the storm-water runoff system of a small suburban watershed is presented together with some data regarding waste-water. 445,000 m3 (34% of the rain-water volume) were drained by the storm-water runoff system and 40,879 m3 by the waste-water system from September 2002 to March 2004. Storm-water runoff is generally not heavily polluted with regard to trace metals but concentrations occasionally exceed the standards for surface water of good quality. On the contrary, pesticides (diuron and glyphosate) have very high concentrations especially in spring and autumn when their use is maximum. As the St Joseph storm-water runoff is finally discharged into the Erdre River, measures to reduce the use of these pollutants should be considered.

scholarly journals THE KINETICS OF THE DECOMPOSITION OF PEROXIDE BY CATALASE

1925 ◽  
Vol 7 (3) ◽  
pp. 373-387 ◽  
Author(s):  
John H. Northrop
Keyword(s):  
Hydrogen Peroxide ◽  
Experimental Results ◽  
Inactivation Rate ◽  
High Concentration ◽  
Inactivation Constant ◽  
Monomolecular Decomposition ◽  
High Concentrations ◽  
Kinetics Of ◽  
Very High

It has been shown that the experimental results obtained by Morgulis in a study of the decomposition of hydrogen peroxide by liver catalase at 20°C. and in the presence of an excess of a relatively high concentration of peroxide are quantitatively accounted for by the following mechanisms. 1. The rate of formation of oxygen is independent of the peroxide concentration provided this is greater than about 0.10 M. 2. The rate of decomposition of the peroxide is proportional at any time to the concentration of catalase present. 3. The catalase undergoes spontaneous monomolecular decomposition during the reaction. This inactivation is independent of the concentration of catalase and inversely proportional to the original concentration of peroxide up to 0.4 M. In very high concentrations of peroxide the inactivation rate increases. 4. The following equation can be derived from the above assumptions and has been found to fit the experiments accurately. See PDF for Equation in which x is the amount of oxygen liberated at the time t, A is the total amount of oxygen liberated (not the total amount available), and K is the inactivation constant of the enzyme.

Direct observations of radiation-enhanced transformations in glass

1983 ◽  
Vol 41 ◽  
pp. 354-355
Author(s):  
J. F. DeNatale ◽  
D. G. Howitt
Keyword(s):  
Glass Matrix ◽  
Diffusion Mechanism ◽  
Bubble Formation ◽  
Silicate Glasses ◽  
Phase Decomposition ◽  
Direct Observations ◽  
Thin Foils ◽  
Oxygen Bubble ◽  
Electron Energy Loss ◽  
Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

The effect of heterotrophic yield on the assessment of the correction factor for anoxic growth

1996 ◽  
Vol 34 (5-6) ◽  
pp. 67-74 ◽  
Author(s):  
D. Orhon ◽  
S. Sözen ◽  
N. Artan
Keyword(s):  
Correction Factor ◽  
Domestic Sewage ◽  
Yield Coefficient ◽  
Heterotrophic Growth ◽  
Metabolic Processes ◽  
Anoxic Conditions ◽  
Industrial Wastewaters ◽  
Systems Modelling ◽  
Kinetics Of ◽  
Very High

For single-sludge denitrification systems, modelling of anoxic reactors currently uses the kinetics of aerobic heterotrophic growth together with a correction factor for anoxic conditions. This coefficient is computed on the basis of respirometric measurements with the assumption that the heterotrophic yield remains the same under aerobic and anoxic coditions. The paper provides the conceptual proof that the yield coefficient is significantly lower for the anoxic growth on the basis of the energetics of the related metabolic processes. This is used for the interpretation of the very high values for the correction factor experimentally determined for a number of industrial wastewaters. A default value for the anoxic heterotrophic yield coefficient is calculated for domestic sewage and compatible wastewaters and proposed for similar evaluations.

Relations between carbon removal rates, biofilm size and density of a novel anaerobic reactor: the inverse turbulent bed

2000 ◽  
Vol 41 (4-5) ◽  
pp. 253-260 ◽  
Author(s):  
P. Buffière ◽  
R. Moletta
Keyword(s):  
Removal Rate ◽  
Removal Rates ◽  
Carbon Removal ◽  
Biofilm Growth ◽  
Loading Rates ◽  
Biomass Activity ◽  
High Turbulence ◽  
The One ◽  
High Level ◽  
Very High

An anaerobic inverse turbulent bed, in which the biogas only ensures fluidisation of floating carrier particles, was investigated for carbon removal kinetics and for biofilm growth and detachment. The range of operation of the reactor was kept within 5 and 30 kgCOD· m−3· d−1, with Hydraulic Retention Times between 0.28 and 1 day. The carbon removal efficiency remained between 70 and 85%. Biofilm size were rather low (between 5 and 30 μm) while biofilm density reached very high values (over 80 kgVS· m−3). The biofilm size and density varied with increasing carbon removal rates with opposite trends; as biofilm size increases, its density decreases. On the one hand, biomass activity within the reactor was kept at a high level, (between 0.23 and 0.75 kgTOC· kgVS· d−1, i.e. between 0.6 and 1.85 kgCOD·kgVS · d−1).This result indicates that high turbulence and shear may favour growth of thin, dense and active biofilms. It is thus an interesting tool for biomass control. On the other hand, volatile solid detachment increases quasi linearly with carbon removal rate and the total amount of solid in the reactor levels off at high OLR. This means that detachment could be a limit of the process at higher organic loading rates.

The metachor as a characteristic of the association of electrolytes in aqueous solutions

1984 ◽  
Vol 49 (5) ◽  
pp. 1061-1078 ◽  
Author(s):  
Jiří Čeleda ◽  
Stanislav Škramovský
Keyword(s):  
Aqueous Solutions ◽  
Apparent Volume ◽  
Solutions Of Electrolytes ◽  
Molal Volumes ◽  
The Difference ◽  
High Concentrations ◽  
Experimental Values ◽  
Suitable Characteristic ◽  
Association Of Ions ◽  
Very High

Based on the earlier paper introducing a concept of the apparent parachor of a solute in the solution, we have eliminated in the present work algebraically the effect which is introduced into this quantity by the additivity of the apparent molal volumes. The difference remaining from the apparent parachor after substracting the contribution corresponding to the apparent volume ( for which the present authors suggest the name metachor) was evaluated from the experimental values of the surface tension of aqueous solutions for a set of 1,1-, 1,2- and 2,1-valent electrolytes. This difference showed to be independent of concentration up to the very high values of the order of units mol dm-3 but it was directly proportional to the number of the free charges (with a proportionality factor 5 ± 1 cm3 mol-1 identical for all studied electrolytes). The metachor can be, for this reason, a suitable characteristic for detection of the association of ions and formation of complexes in the solutions of electrolytes, up to high concentrations where other methods are failing.

scholarly journals Nitrification Process in a Nuclear Wastewater with High Load of Nitrogen, Uranium and Organic Matter under ORP Controlled

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1607
Author(s):  
Mariano Venturini ◽  
Ariana Rossen ◽  
Patricia Silva Paulo
Keyword(s):  
Ammonia Oxidation ◽  
High Load ◽  
Nuclear Fuels ◽  
Monod Model ◽  
Nernst Equation ◽  
Nitrification Process ◽  
Real Wastewater ◽  
High Concentrations ◽  
Wastewater Samples ◽  
Very High

To produce nuclear fuels, it is necessary to convert uranium′s ore into UO2-ceramic grade, using several quantities of kerosene, methanol, nitric acid, ammonia, and, in low level, tributyl phosphate (TBP). Thus, the effluent generated by nuclear industries is one of the most toxic since it contains high concentrations of dangerous compounds. This paper explores biological parameters on real nuclear wastewater by the Monod model in an ORP controlled predicting the specific ammonia oxidation. Thermodynamic parameters were established using the Nernst equation to monitor Oxiders/Reductors relationship to obtain a correlation of these parameters to controlling and monitoring; that would allow technical operators to have better control of the nitrification process. The real nuclear effluent is formed by a mixture of two different lines of discharges, one composed of a high load of nitrogen, around 11,000 mg/L (N-NH4+-N-NO3−) and 600 mg/L Uranium, a second one, proceeds from uranium purification, containing TBP and COD that have to be removed. Bioprocesses were operated on real wastewater samples over 120 days under controlled ORP, as described by Nernst equations, which proved to be a robust tool to operate nitrification for larger periods with a very high load of nitrogen, uranium, and COD.

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