Initial substrate concentration

Equation 1-106 predicts that the initial rate will be proportional to the initial enzyme concentration, if the initial substrate concentration is held constant. If the initial enzyme concentration is held constant, then the initial rate will be proportional to the substrate concentration at low substrate concentrations and independent of the substrate concentration at high substrate levels. The maximum reaction rate for a given total enzyme concentration is... 

During electrochemical fluorination retention of important functional groups or atoms in molecules is essential. Acyl fluorides and chlorides, but not carboxylic acids and anhydrides (which decarboxylate), survive perfluorination to the perfluorinated acid fluorides, albeit with some cyclization in longer chain (>C4) species [73]. Electrochemical fluorination of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluorination of octanoyl chloride results in perfluorinated cyclic ethers as well as perfluorinated octanoyl fluonde. Cyclization decreases as initial substrate concentration increases and has been linked to hydrogen-bonded onium polycations [73]. Cyclization is a common phenomenon involving longer (>C4) and branched chains. a-Alkyl-substituted carboxylic acid chlorides, fluorides, and methyl esters produce both the perfluorinated cyclic five- and six-membered ring ethers as well as the perfluorinated acid... 

Monod kinetics are considered in a CSTR with an organism growing with an initial substrate concentration of 50g-l 1 and kinetic parameters of Ks = 2g-l 1 and /Amax = 0.5lr. (a) What would be the maximum dilution rate for 100% yield of biomass with maximum rate (b) If the same dilution is used, what would be number of CSTRs in series ... 

Fig. 5.22. Dixon plot 1/v versus [P] at different initial substrate concentrations.

When the cell concentration is appreciable, the dilution rate must reach a specific rate (X / 0, D = ft). The cell mass concentration is defined in (6.8.1.13) as the dilution rate approaches zero the cell density is the product of yield and initial substrate concentration ... 

After differentiation, the result is simplified for initial substrate concentration with respect to dilution rate ... 

The Monod rate model is valid for a CSTR bioreactor with maximum specific growth rate of 0.5 li 1 and K, 2 g-1. What would be a suitable dilution rate at steady-state condition, where there is no cell death if initial substrate concentration is 50g-l-1 and yield of biomass on substrate is 100%. 

Fig. 8.13. Glucose concentration and ethanol production versus retention time in immobilised cell reactor with initial substrate concentration of 150 g l1 glucose. Reprinted from Najafpour et al. (2004).18 Copyright with permission from Elsevier.

A 20 m3 working volume of bioreactor is used for production of penicillin. What is the initial substrate concentration, S0, that you choose when there is a limitation in sufficient oxygen transfer rate and there are no limiting reactants ... 

The initial rate is written as v and the initial substrate concentration as [S]o. The limiting rate at high [S] is designated Vmax- The constant Km, known as the Michaelis... 

From the Michaelis-Menten model, there is a relationship between 1/Fo and the initial substrate concentration, expressed as the reciprocal, 1/[Bq]. To develop this relationship we shall repeat Example 9.1 using varying concentrations of B cells. Be sure to subtract the number of Bq cells in each study from the total number of water, D, cells in the setup. 

The optimal feeding profile based on the model is shown in Figure 3 and the simulation profiles are shown in Figure 4 for initial substrate concentrations of 90 mM benzaldehyde and 108 mM sodium pyruvate, and initial PDC activity of 4.0 U ml carboligase. Feeding was programmed at hourly intervals and the initial reaction volume would increase by 50% by the end of the simulated biotransformation. 

Available methods provide measurements of enzyme activity rather than of enzyme concentration. In order that the measured activity be proportional to enzyme concentration, the reaction conditions which include pH, temperature, initial substrate concentration, sample and total volume and reaction time must be held constant and be carefully controlled. 

The Michaelis constant is numerically equal to the value of the initial substrate concentration that gives an initial velocity that is half that of the maximum. 

In both cases the initial substrate concentration was 0.14 kmole/m3. In cases A and B the Michaelis constants (Km) are reported to be 1.15 x 10-3 and 1.5 x 10-3 kmoles/m3, respectively. The rate constant k3 is equal to 1.25 jumoles/m3 sec unit in both cases. 

Y )- Benzyl morpholine is a potent appetite suppressant drug. The synthesis of 2-(/ )-benzyl-morpholine began with the reduction of the unsaturated bromocinnamaldehyde to the corresponding saturated (X)-bromo-alcohol by baker s yeast, with a very low ee of 63%. However, an efficient transformation can be achieved by controlling the substrate concentration with the addition of hydrophobic resin Amberlite XAD-1180 [26]. With a resin-to-substrate ratio of one and an initial substrate concentration of 5 gL, the saturated (X)-bromo-alcohol was recovered at nearly quantitative yield and 98.6% ee. 

From scheme I, together with the experimentally observed first-order dependence on the total ester concentration, the rate relationship illustrated in Eq. (1) may be derived. In applying this equation, the cycloamylose concentration must be at least tenfold greater than the initial substrate concentration to ensure first-order conditions. Equation (1) may be rearranged in two ways to yield linear forms which permit graphical evaluation of fa, the maximal rate constant for release of phenol from the fully com-plexed ester and Kd, the cycloamylose-substrate dissociation constant (defined in Scheme I as A i/fa). These two methods are illustrated in Eqs. (2) and (3) and may be attributed to Lineweaver and Burk (1934) and to Eadie (1942), respectively. Although in theory both methods should give... 

The initial velocity is measured at a series of different substrate concentrations. In all cases the concentration of substrate used is much higher (by thousands of times, usually) than that of the enzyme. Each substrate concentration requires a separate measurement of the initial velocity. At low concentrations of substrate, increasing the substrate concentration increases the velocity of the reaction, but at high substrate concentrations, increasing the initial substrate concentration does not have much of an effect on the velocity (Fig. 8-4). 

As the initial substrate concentration becomes higher and higher, at some concentration, the substrate is so easy to find that all the enzyme active sites are occupied with bound substrate (or product). The enzyme is termed saturated at this point, and further increases in substrate concentration will not make the reaction go any faster. With [S] > Km, the velocity approaches ymax. 

The results of the kinetic analysis for the investigated systems are summarized in Table 10.2, the substrate concentration used being the same for all trials. In the case of methyl- and cyclohexyl-substituted ligands the Michaelis constant is smaller than the initial substrate concentration of [S]o=0.06666 mol L-1 (Table 10.2). However, a description of the hydrogenations with other catalyst ligands as first-order reactions shows that in each of these cases the Michaelis constant must be much greater than the experimentally chosen substrate concentration. 

These results, obtained from the gross-hydrogen consumption under normal conditions on the basis of the model developed above, make it clear that even catalysts of the same basic type can give rise to considerably different pre-equilibria. As a consequence, comparison of activities of various catalytic systems under standard conditions can provide the wrong picture. Hence, the cyclohexyl precatalyst with dimethyl itaconate seems to be the most active one (by reference to Fig. 10.13). Nonetheless, an increase in the initial substrate concentration by a factor of ten already leads to a different order in activity. 

Hydrolysis of methyl hydrocinnamate is catalyzed by the enzyme chymotripsin. Data were obtained at 25 C with pH k7.6 and a constant enzyme concentration. These are of initial reaction rate, mol/1iter-sec, and corresponding initial substrate concentrations. Find the Michaelis-Menten constants. 

Probably the most important variable to consider in defining optimal conditions or standard conditions is the initial substrate concentration. Most enzymes show a hyperbolic curve as relation between initial reaction velocity and substrate concentration, well known now as the Michaelis-Menten curve. With increasing substrate concentration (S) the velocity (o) rises asymptotically to a maximum value (V) (Fig. 3), according to the expression ... 

Also vary the initial substrate concentration, i.e. the degree of contamination in the range 1.0xlO-6 to 0.1, and see how this influences the bioremediation time. 

Kinetics of the photooxidation of organic water impurities on illuminated titania surfaces has been generally regarded to be based on the Langmuir-Hinshelwood equation with first-order reaction kinetics vs. initial substrate concentration was established univocally by many authors... 

J. Phys. Chem., in press]. From continuous radiolysis experiments, we have determined the yields of hydrogen and rhodium(I) as functions of pH, initial substrate concentration, and absorbed dose. 

Most of the studies05,20 271 show that a correlation between culture fluorescence and biomass concentration can be obtained mainly in the exponential growth phase. In addition, in order to obtain reproducible correlations, all of the fermentation conditions such as initial substrate concentration, pH, dissolved oxygen level, temperature, and agitation rate have to be the same. However, once the culture is past exponential growth, biomass measurement by following culture fluorescence is no longer accurate. 

It may also improve the likelihood of detecting enzyme activity if substrate concentration is increased. This approach is useful only if the initial substrate concentration is below (the Michaelis constant see O Section 4.1.2) because enzyme activity can only be doubled from that at even if the substrate concentration is increased to infinitely high levels. Furthermore, in many assay systems, blank readings are proportional to substrate concentration, and there is little to be gained by a tenfold increase in [S] that results in a 70% increase in v and a 1,000% increase in the blank signal. 

Rule 1. Upon obtaining a double-reciprocal plot of 1/v vx. 1/[A] (where [A] is the initial substrate concentration and V is the initial velocity) at varying concentrations of the inhibitor (I), if the vertical intercept varies with the concentration of the reversible inhibitor, then the inhibitor can bind to an enzyme form that does not bind the varied substrate. For example, for the simple Uni Uni mechanism (E + A EX E -P P), a noncompetitive or uncompetitive inhibitor (both of which exhibit changes in the vertical intercept at varying concentrations of the inhibitor), I binds to EX, a form of the enzyme that does not bind free A. In such cases, saturation with the varied substrate will not completely reverse the inhibition. 

A graphical procedure " for plotting enzyme initial rate data as v versus v/[S] (also known as the Woolf-Au-gustinsson-Hofstee plot), where the initial velocity v is the so-called (y)-axis variable and v divided by the initial substrate concentration [S] is the so-called (v)-axis variable, such that the vertical-axis intercept equals Vmax, the slope equals and the horizontal-axis intercept is V IK... 

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