scholarly journals Preparation and Kinetic Studies of Cross-Linked Chitosan Beads Using Dual Crosslinkers of Tripolyphosphate and Epichlorohydrin for Adsorption of Methyl Orange

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Akhmad Sabarudin ◽  
Armeida D. R. Madjid
Keyword(s):  
Methyl Orange ◽  
Bulk Diffusion ◽  
Kinetic Studies ◽  
Hydroxyl Group ◽  
High Concentration ◽  
Chitosan Beads ◽  
Kinetics Of Adsorption ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Preparation of cross-linked chitosan beads using dual crosslinkers of tripolyphosphate (TPP) and epichlorohydrin (ECH) for the adsorption and kinetic studies of methyl orange (MO) had been carried out. FTIR spectra showed that TPP could act as the protecting agent of the NH2 group of chitosan and ECH reacted with the primary hydroxyl group of chitosan. Various concentrations of TPP, ECH, and immersing time in the TPP solution for bead formation were studied. The effect of pH and kinetics of adsorption were investigated to define the mechanism of adsorption and rate-limiting step. As a result, pH 3, 10% (w/v) TPP, 5% (v/v) ECH, and 12 h immersing time in TPP were selected as the optimum conditions for preparing the beads as indicated by the highest adsorption amount of MO. The cross-linked chitosan beads’ adsorption capacity for MO under optimum condition was found to be 79.55 mg/g with the adsorption rate constant (k) of 1.29 × 10−3/min. Furthermore, it was found that a low concentration of ECH could maintain the stability of chitosan in acidic conditions, whereas the concentration of TPP and immersing time controlled pore size and morphology of chitosan beads. The mechanism of adsorption of MO was controlled by the pore and rigidity of cross-linked chitosan beads. Bulk diffusion acted as a rate-limiting step, and a high concentration of MO inhibited diffusion and adsorption itself.

A Kinetic Study on the Methanogenesis Process in Anaerobic Digestion

1989 ◽  
Vol 21 (4-5) ◽  
pp. 175-186 ◽  
Author(s):  
C. Y. Lin ◽  
T. Noike ◽  
H. Furumai ◽  
J. Matsumoto
Keyword(s):  
Anaerobic Digestion ◽  
Substrate Concentration ◽  
Volatile Fatty Acid ◽  
Kinetic Mechanism ◽  
High Concentration ◽  
Two Phase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
The Relationship ◽  
Rate Limiting

Results obtained from experiments on two-phase anaerobic digestion using a high concentration of a volatile fatty acid (VFA) mixture were used to elucidate the kinetic mechanism of the methanogenesis process. The mixture consisted of the major intermediate products of anaerobic digestion, i.e., acetic acid (HAc), propionic acid (HPr) and butyric acid (HBu). The relationship between the rate of substrate utilization and substrate concentration in the digesters was in the form of a Michaelis-Menten equation. The rate-limiting step of the methanogenesis process, i.e., the conversion of HAc to methane, was speeded up in the digesters and this was proved kinetically. A method for determining kinetic constants for substrate-specific microorganisms was suggested. A simulation model for predicting the effluent substrate concentration was demonstrated. The effluent substrate concentration of an anaerobic digester fed by a multisubstrate was found to be simulatively predictable from its influent component substrates.

scholarly journals Oxidation of Cytochrome 605 Is the Rate-Limiting Step when Ferrimicrobium acidiphilum Respires Aerobically on Soluble Iron

2020 ◽  
Vol 86 (22) ◽  
Author(s):  
Robert C. Blake ◽  
Jessie J. Guidry ◽  
Micah D. Anthony ◽  
Bhupal Ban ◽  
Kayla A. Smith ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Ferrous Ions ◽  
Gram Positive ◽  
Oxidase Gene ◽  
Physiological Conditions ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Intact Organism ◽  
Rate Limiting

ABSTRACT Proteins that oxidize extracellular substrates in Gram-positive bacteria are poorly understood. Ferrimicrobium acidiphilum is an actinobacterium that respires aerobically on extracellular ferrous ions at pH 1.5. In situ absorbance measurements were conducted on turbid suspensions of intact Fm. acidiphilum using an integrating cavity absorption meter designed for that purpose. Initial velocity kinetic studies monitored the appearance of product ferric ions in the presence of catalytic quantities of cells. Cell-catalyzed iron oxidation obeyed the Michaelis-Menten equation with Km and Vmax values of 71 μM and 0.29 fmol/min/cell, respectively. Limited-turnover kinetic studies were conducted with higher concentrations of cells to detect and monitor changes in the absorbance properties of cellular redox proteins when the cells were exposed to limited quantities of soluble reduced iron. A single a-type cytochrome with reduced absorbance peaks at 448 and 605 nm was the only redox-active chromophore that was visible as the cells respired aerobically on iron. The reduced cytochrome 605 exhibited mathematical and correlational properties that were consistent with the hypothesis that oxidation of the cytochrome constituted the rate-limiting step in the aerobic respiratory process, with a turnover number of 35 ± 2 s−1. Genomic and proteomic analyses showed that Fm. acidiphilum could and did express only two a-type heme copper terminal oxidases. Cytochrome 605 was associated with the terminal oxidase gene that is located between nucleotides 31,090 and 33,039, inclusive, in the annotated circular genome of this bacterium. IMPORTANCE The identities and functions of proteins involved in aerobic respiration on extracellular ferrous ions at acidic pH are poorly understood in the four phyla of Gram-positive eukaryotes and archaea where such activities occur. In situ absorbance measurements were conducted on Fm. acidiphilum as it respired on extracellular iron using an integrating cavity absorption meter that permitted accurate optical measurements in turbid suspensions of the intact bacterium under physiological conditions. The significance of these measurements is that they permitted a direct spectrophotometric examination of the extents and rates of biological electron transfer events in situ under noninvasive physiological conditions without disrupting the complexity of the live cellular environment. One thing is certain: one way to understand how a protein functions in an intact organism is to actually observe that protein as it functions in the intact organism. This paper provides an example of just such an observation.

Study of Adsorption of Cu2+ and Ni2+ from Aqueous Solutions Using β-Cyclodextrin Modified Zeolites

2014 ◽  
Vol 955-959 ◽  
pp. 3509-3513
Author(s):  
Xiao Hong Li ◽  
Xue Kui Hao
Keyword(s):  
Contact Time ◽  
Physical Adsorption ◽  
Kinetic Studies ◽  
Order Model ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Adsorption Processes ◽  
Pseudo Second Order ◽  
Modified Zeolites ◽  
Rate Limiting

Adsorption of Cu2+ and Ni2+ from aqueous solution on CCDMZ was investigated. The adsorption capacity of Cu2+ and Ni2+ on CCDMZ was found to have a much higher enhance than that of NZ and to be obviously influenced by contact time, initial concentration and pH. The kinetic studies showed that the adsorption processes of Cu2+ and Ni2+ on CCDMZ were complex, including chemical adsorption and physical adsorption. The adsorption followed the pseudo-second-order model, which suggested that the rate-limiting step might be mainly chemisorption.

THE Δ5-3β-HYDROXYSTEROID DEHYDROGENASE OF BOVINE ADRENAL MICROSOMES

1969 ◽  
Vol 43 (4) ◽  
pp. 599-608 ◽  
Author(s):  
A. M. NEVILLE ◽  
J. C. ORR ◽  
L. L. ENGEL
Keyword(s):  
Dehydrogenase Activity ◽  
Kinetic Studies ◽  
Hydroxysteroid Dehydrogenase ◽  
Acetone Powder ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Michaelis Constants ◽  
Rate Limiting

SUMMARY The Δ5-3β-hydroxysteroid dehydrogenase activity of an acetone powder of bovine adrenal microsomes has been studied using 3β-hydroxyandrost-5-en-17-one and 3β-hydroxypregn-5-en-20-one as substrates. The products were separated, identified and quantitated by gas—liquid chromatographymass spectrometry. The Michaelis constants for both steroid substrates and for NAD have been derived and are of the order of 10−6 m. Although kinetic studies indicate the existence of a single Δ5-3β-hydroxysteroid dehydrogenase, the possibility of a non-enzymic rate-limiting step common to both steroid substrates and to NAD must be entertained.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

Dynamics of hepatic and peripheral insulin effects suggest common rate-limiting step in vivo

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman
Keyword(s):  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting
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