Framework of the kinetic analysis of O2-dependent oxidative biocatalysts for reaction intensification

2021 ◽  
Author(s):  
Alvaro Lorente-Arevalo ◽  
Miguel Ladero ◽  
Juan M. Bolivar
Keyword(s):  
Enzyme Activity ◽  
Kinetic Analysis ◽  
Oxygen Limitation ◽  
Oxygen Solubility ◽  
Low Oxygen

The application of oxygen-dependent enzymes is limited by the low oxygen solubility, a fact that hinders the full operational exploitation of the enzyme activity. This oxygen limitation also creates a...

Hydrocarbon biodegradation in oxygen-limited sequential batch reactors by consortium from weathered, oil-contaminated soil

2005 ◽  
Vol 51 (3) ◽  
pp. 231-239 ◽  
Author(s):  
S A Medina-Moreno ◽  
S Huerta-Ochoa ◽  
M Gutiérrez-Rojas
Keyword(s):  
Contaminated Soil ◽  
Batch Reactor ◽  
Oxygen Limitation ◽  
Total Petroleum Hydrocarbons ◽  
Hydrocarbon Biodegradation ◽  
Batch Reactors ◽  
Native Plant ◽  
Low Oxygen ◽  
Bacterial Strains ◽  
Transfer Coefficients

We studied the use of sequential batch reactors under oxygen limitation to improve and maintain consortium ability to biodegrade hydrocarbons. Air-agitated tubular reactors (2.5 L) were operated for 20 sequential 21-day cycles. Maya crude oil – paraffin mixture (13 000 mg/L) was used as the sole carbon source. The reactors were inoculated with a consortium from the rhizosphere of Cyperus laxus, a native plant that grows naturally in weathered, contaminated soil. Oxygen limitation was induced in the tubular reactor by maintaining low oxygen transfer coefficients (kLa < 20.6 h–1). The extent and biodegradation rates increased significantly up to the fourth cycle, maintaining values of about 66.33% and 460 mg·L–1·d–1, respectively. Thereafter, sequential batch reactor operation exhibited a pattern with a constant general trend of biodegradation. The effect of oxygen limitation on consortium activity led to a low biomass yield and non-soluble metabolite (0.45 g SS/g hydrocarbons consumed). The average number of hydrocarbon-degrading microorganisms increased from 6.5 × 107 (cycles 1–3) to 2.2 × 108 (cycles 4–20). Five bacterial strains were identified: Achromobacter (Alcaligenes) xylosoxidans, Bacillus cereus, Bacillus subtilis, Brevibacterium luteum, and Pseudomonas pseudoalcaligenes. Asphaltene-free total petroleum hydrocarbons, extracted from a weathered, contaminated soil, were also biodegraded (97.1 mg·L–1·d–1) and mineralized (210.48 mg CO2·L–1·d–1) by the enriched consortium without inhibition. Our results indicate that sequential batch reactors under oxygen limitation can be used to produce consortia with high and constant biodegradation ability for industrial applications of bioremediation.Key words: sequential batch reactors, oxygen limitation, consortium, hydrocarbon biodegradation.

Mesozooplankton community in a seasonally hypoxic and highly eutrophic bay

2015 ◽  
Vol 66 (8) ◽  
pp. 719 ◽  
Author(s):  
Min-Chul Jang ◽  
Kyoungsoon Shin ◽  
Pung-Guk Jang ◽  
Woo-Jin Lee ◽  
Keun-Hyung Choi
Keyword(s):  
High Temperature ◽  
Bottom Water ◽  
Oxygen Solubility ◽  
Low Oxygen ◽  
Negative Effects ◽  
Mesozooplankton Community ◽  
Seawater Chemistry ◽  
Hypoxic Conditions ◽  
Bottom Waters ◽  
Major Factors

A 2-year survey of seawater chemistry and mesozooplankton abundance was carried out in Masan Bay, South Korea, one of the most eutrophic coastal ecosystems known. The study aimed to identify the major factors contributing to the seasonally persistent hypoxia in the bay, to characterise the Bay’s mesozooplankton community and to examine the effects of low oxygen on the distribution of mesozooplankton. Hypoxia (<2mgO2L–1) was present only in summer, with ultrahypoxia (<0.2mg O2 L–1) in the bottom waters of the inner bay in both years. Low summer oxygen can be attributed to high summer phytoplankton stocks, together with reduced oxygen solubility at high temperature and stratification of the water column that limits downward diffusion of oxygen. A seasonally and spatially distinct mesozooplankton community was identified in summer when there was greater influence of freshwater discharge in the inner bay. Marine cladocerans were very abundant, with a population outburst of Penilia avirostris in the inner bay (>4000 individuals m–3) during summer. During hypoxic events, the abundance of Penilia avirostris was positively related to oxygen levels in the bottom water, suggesting that hypoxic conditions may cause mortality or have sublethal negative effects on population growth of this filter-feeding cladoceran.

scholarly journals Uremic plasma contains factors inhibiting 1 alpha-hydroxylase activity.

1992 ◽  
Vol 3 (4) ◽  
pp. 947-952
Author(s):  
C H Hsu ◽  
S Patel
Keyword(s):  
Enzyme Activity ◽  
Kinetic Analysis ◽  
Normal Saline ◽  
Saline Solution ◽  
Uremic Toxin ◽  
Enzyme Kinetic ◽  
Hydroxylase Activity ◽  
Normal Plasma ◽  
Guanidinosuccinic Acid ◽  
Plasma Ultrafiltrate

The effect of uremic plasma ultrafiltrate on calcitriol synthesis was investigated. Renal 1 alpha-hydroxylase activity was measured in normal rats infused for 20 h with 20 mL of normal or uremic plasma ultrafiltrate. Renal 1 alpha-hydroxylase activity was determined by the generation of calcitriol measured 5, 10, 20, and 30 min after the reaction was initiated by the addition of cold 25(OH)D3. The activity was significantly lower in rats infused with uremic plasma ultrafiltrate. Kidney homogenates preincubated for 3 h with uremic plasma ultrafiltrate also had significantly lower renal 1 alpha-hydroxylase activity than did those preincubated with normal plasma ultrafiltrate. In addition, the effect of the putative uremic toxin, guanidinosuccinic acid (GSA), on renal 1 alpha-hydroxylase activity was studied. Normal rats infused for 20 h with 20 mL of saline solution containing 1.5 mg/dL of GSA had significantly lower renal 1 alpha-hydroxylase activity than did rats infused with normal saline. The enzyme activity was also lower in kidney homogenates preincubated for 3 h with 4 mg/dL of GSA. Enzyme kinetic analysis revealed that the inhibition of renal 1 alpha-hydroxylase by GSA was noncompetitive. It was concluded that uremic plasma contains substances that directly inhibit renal 1 alpha-hydroxylase activity.

scholarly journals Autothermal Thermophilic Aerobic Digestion (ATAD) for Heat, Gas, and Production of a Class A Biosolids with Fertilizer Potential

2019 ◽  
Vol 7 (8) ◽  
pp. 215
Author(s):  
J. Tony Pembroke ◽  
Michael P. Ryan
Keyword(s):  
Elevated Temperatures ◽  
Dynamic Change ◽  
Oxygen Solubility ◽  
Low Oxygen ◽  
Aerobic Digestion ◽  
Class A ◽  
Pharmaceutical Waste ◽  
Reactor Temperature ◽  
Thermophilic Aerobic Digestion ◽  
Autothermal Thermophilic Aerobic Digestion

Autothermal thermophilic aerobic digestion (ATAD) is a microbial fermentation process characterized as a tertiary treatment of waste material carried out in jacketed reactors. The process can be carried out on a variety of waste sludge ranging from human, animal, food, or pharmaceutical waste where the addition of air initiates aerobic digestion of the secondary treated sludge material. Digestion of the sludge substrates generates heat, which is retained within the reactor resulting in elevation of the reactor temperature to 70–75 °C. During the process, deamination of proteinaceous materials also occurs resulting in liberation of ammonia and elevation of pH to typically pH 8.4. These conditions result in a unique microbial consortium, which undergoes considerable dynamic change during the heat-up and holding phases. The change in pH and substrate as digestion occurs also contributes to this dynamic change. Because the large reactors are not optimized for aeration, and because low oxygen solubility at elevated temperatures occurs, there are considerable numbers of anaerobes recovered which also contributes to the overall digestion. As the reactors are operated in a semi-continuous mode, the reactors are rarely washed, resulting in considerable biofilm formation. Equally, because of the fibrous nature of the sludge, fiber adhering organisms are frequently found which play a major role in the overall digestion process. Here, we review molecular tools needed to examine the ATAD sludge consortia, what has been determined through phylogenetic analysis of the consortia and the nature of the dynamics occurring within this unique fermentation environment.

scholarly journals Degradation of 3-Chlorobenzoate under Low-Oxygen Conditions in Pure and Mixed Cultures of the Anoxygenic Photoheterotroph Rhodopseudomonas palustris DCP3 and an Aerobic Alcaligenes Species

1999 ◽  
Vol 65 (1) ◽  
pp. 131-137 ◽  
Author(s):  
Janneke Krooneman ◽  
Sytske van den Akker ◽  
Teresa M. Pedro Gomes ◽  
Larry J. Forney ◽  
Jan C. Gottschal
Keyword(s):  
Carbon Source ◽  
Molecular Oxygen ◽  
Crucial Role ◽  
Rhodopseudomonas Palustris ◽  
Oxygen Limitation ◽  
Low Oxygen ◽  
Experimental Conditions ◽  
Simultaneous Oxidation ◽  
Oxygen Conditions ◽  
Additional Carbon Source

ABSTRACT The presence or absence of molecular oxygen has been shown to play a crucial role in the degradability of haloaromatic compounds. In the present study, it was shown that anaerobic phototrophic 3-chlorobenzoate (3CBA) metabolism by Rhodopseudomonas palustris DCP3 is oxygen tolerant up to a concentration of 3 μM O2. Simultaneous oxidation of an additional carbon source permitted light-dependent anaerobic 3CBA degradation at oxygen input levels which, in the absence of such an additional compound, would result in inhibition of light-dependent dehalogenation. Experiments under the same experimental conditions with strain DCP3 in coculture with an aerobic 3CBA-utilizing heterotroph, Alcaligenes sp. strain L6, revealed that light-dependent dehalogenation of 3CBA did not occur. Under both oxygen limitation (O2 < 0.1 μM) and low oxygen concentrations (3 μM O2), all the 3CBA was metabolized by the aerobic heterotroph. These data suggest that biodegradation of (halo)aromatics by photoheterotrophic bacteria such as R. palustris DCP3 may be restricted to anoxic photic environments.

scholarly journals Na+/Ca2+ exchange in coated microvesicles

1986 ◽  
Vol 233 (3) ◽  
pp. 643-648 ◽  
Author(s):  
T Saermark ◽  
M Gratzl
Keyword(s):  
Enzyme Activity ◽  
Atpase Activity ◽  
Kinetic Analysis ◽  
Transport System ◽  
Proton Transport ◽  
Ion Accumulation ◽  
Secretory Vesicles ◽  
Proton Permeability ◽  
Total Capacity

Coated microvesicles isolated from bovine neurohypophyses could be loaded with Ca2+ in two different ways, either by incubation in the presence of ATP or by imposition of an outwardly directed Na+ gradient. Na+, but not K+, was able to release Ca2+ accumulated by the coated microvesicles. These results suggest the existence of an ATP-dependent Ca2+-transport system as well as of a Na+/Ca2+ carrier in the membrane of coated microvesicles similar to that present in the membranes of secretory vesicles from the neurohypophysis. A kinetic analysis of transport indicates that the apparent Km for free Ca2+ of the ATP-dependent uptake was 0.8 microM. The average Vmax. was 2 nmol of Ca2+/5 min per mg of protein. The total capacity of microvesicles for Ca2+ uptake was 3.7 nmol/mg of protein. Both nifedipine (10 microM) and NH4Cl (50 mM) inhibited Ca2+ uptake. The ATPase activity in purified coated-microvesicles fractions from brain and neurohypophysis was characterized. Micromolar concentrations of Ca2+ in the presence of millimolar concentrations of Mg2+ did not change enzyme activity. Ionophores increasing the proton permeability across membranes activated the ATPase activity in preparations of coated microvesicles from brain as well as from the neurohypophysis. Thus the enzyme exhibits properties of a proton-transporting ATPase. This enzyme seems to be linked to the ion accumulation by coated microvesicles, although the precise coupling of the proton transport to Ca2+ and Na+ fluxes remains to be determined.

Development of an LC–MS based enzyme activity assay for MurC: application to evaluation of inhibitors and kinetic analysis

2004 ◽  
Vol 35 (4) ◽  
pp. 817-828 ◽  
Author(s):  
Gejing Deng ◽  
Rong-Fang Gu ◽  
Stephen Marmor ◽  
Stewart L. Fisher ◽  
Haris Jahic ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Kinetic Analysis ◽  
Activity Assay ◽  
Enzyme Activity Assay

scholarly journals Low Oxygen and Elevated Carbon Dioxide Atmospheres Inhibit Ethylene Biosynthesis in Preclimacteric and Climacteric Apple Fruit

1997 ◽  
Vol 122 (4) ◽  
pp. 542-546 ◽  
Author(s):  
James R. Gorny ◽  
Adel A. Kader
Keyword(s):  
Enzyme Activity ◽  
Mrna Level ◽  
Acc Oxidase ◽  
Acc Synthase ◽  
Transcript Abundance ◽  
Ethylene Biosynthesis ◽  
Apple Fruit ◽  
Low Oxygen ◽  
Rate Limiting Step

Autocatalytic C2H4 biosynthesis in preclimacteric apple fruit (Malus domestica Borkh. `Golden Delicious') was prevented by storage in atmospheres of 20% CO2-enriched air (17% O2 + 63% N2) or 0.25% O2 (balance N2). In preclimacteric fruit, both treatments inhibited C2H2 biosynthesis by suppressing expression of ACC synthase (ACC-S) at the mRNA level. ACC oxidase (ACC-O) mRNA abundance and in vitro enzyme activity also were impaired by these treatments. However, the conversion of ACC to C2H4 never became the rate limiting step in C2H4 biosynthesis. C2H4 biosynthesis also was effectively inhibited in climacteric apple fruit kept in air + 20% CO2 or 0.25% O2. Climacteric apples also exhibited suppressed expression of ACC-S at the mRNA level, while ACC-O transcript abundance, enzyme activity, and protein abundance were reduced only slightly. ACC-S is the key regulatory enzyme of C2H4 biosynthesis and is the major site at which elevated CO2 and reduced O2 atmospheres inhibit C2H4 biosynthesis, irrespective of fruit physiological maturity. Chemical names used: 1-aminocyclopropane-1-carboxcylic acid (ACC).

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