Effect of product inhibition

The continuous sweeping of the zeolite catalyst by the feed limits the negative effect of product inhibition. 

Perrier, D. Ashley, J. Levy, G. "Effect of Production Inhibition on Kinetics of Druq Elimination," J. Pharm. Biopharm., 1973, 1, 231-242... 

So far, the effect of product inhibition has not been considered. Inhibited enzyme electrodes have been discussed in a collection of publications by Albery et at. [42, 44, 45]. Solving our equations by applying a steady-state analysis, and including the effects of product inhibition within the film, results in the following expression for the homogeneous reaction flux, f, within the polymer layer [48],... 

Figure 2.27 shows a set of responses to NADH recorded for different concentrations of NAD + in the bulk solution. In this case, we analyse the data taking account of the effects of product inhibition. The solid lines in Fig. 2.27 are the best fits of the data to the expression for the current across the Case II/IV boundary taking account of product inhibition (that... 

T he literature on pyrolysis of paraffin hydrocarbons is extensive. A recent review (1) of propane pyrolysis lists 103 references covering a period from 1928 to 1976. The study indicates a remarkable lack of quantitative agreement on energies of activation and on the effect of product inhibition on rate of decomposition. Energies of activation, from reputable experimental efforts, cover a range from 40 to 80 kcal/mol. 

First efforts to take into account the effects of product inhibition resulted in a fairly simple equation (termed the product inhibition or PI model). 

Fig. 23.7. Dynamics of an enzymatic reaction in lipid nanotube networks with variable topology numeric calculations (bottom)/fluorescence intensity of the reaction product (top) vs. time for three differently chosen network geometries, (a) Reference experiment a static four-vesicle network. The product concentration displays a cascade-like behavior in time and space, (b) Linear-to-circular topology change in the four-vesicle network (c) A model study of the effect of product inhibition as the linear four-vesicle network (top panel) undergoes the same change in structure (bottom panel) as the network in the reference experiment ([28], reprinted with permission)...

A very common variation of the CSTR is a cascade of n CSTRs. With an increasing number of reaction vessels, the cascade approximates to the plug-flow reactor. The product concentration increases stepwise from vessel to vessel. For example, a two-stage cascade can be used to overcome effects of product inhibition, e.g. in the synthesis of L-tert-leucine 1421 or GDP-Manl144, 145l The basis for calculating reactor operation conditions is the formulation of mass balances for all reaction components for the distinct reactor type. The mass balances for the above reactors can be formulated as follows ... 

A distinction between mechanisms I and III can be made by measuring the effect of product inhibition on the initial rate. (Note that for the random, rapid equilibration mechanism, 4 = 203/0i unfortunately the experimental precision is generally not sufficient to utilize this relationship as a reliable mechanistic indicator.) Thus experiments can be carried out with varying concentrations of A, B, and C in the absence of D and with varying concentrations of A, B, and D in the absence of C. The steady-state initial velocities for mechanism I for these two cases are... 

The difference between batch and continuous culture techniques with respect to the effect of product inhibition is that under the conditions of continuous cultures product is diluted, while in batch runs product is accumulated. Therefore, in batch cultures reaction rates eventually slow down. In chemostat cultures, however, oscillations of x and p appear due to periodic effect of, for example, pH control and/or permanent inflow and outflow of fresh medium. For the mathematical modeling and computer simulation of this problem, it is possible to formulate the following differential equations ... 

Precious metal based water-gas shift catalysts have zero reaction order for carbon monoxide below 300 ° C, which means that the rate of conversion is not affected by the carbon monoxide concentration in the low temperature range [57,303]. This is not the situation for the copper/zinc oxide catalysts described above [304]. However, the products carbon dioxide and hydrogen have an inhibiting effect on the reaction in the low temperature range for both types of catalysts [305, 304]. Many publications in the field of water-gas shift catalysts do not take these effects into consideration, which impairs the applicability of the results considerably. Frequently only carbon monoxide and steam are fed to the catalyst samples and the activity is determined while ignoring the effects of product inhibition. 

The same authors reports [13] the a/p inversion of the C-3 hydroxyl of numerous bile acids with different lengths of the side chain (1, 31, 34, 37, 40, 43, 46, and 49) [6,9,10]. Inversion was obtained in two steps through the sequential use of die commercial enzymes 3a- and 3P-HSDH, employed in the free form, or immobilized on Eupergit G. The effects of product inhibition on reaction rates, as well as the favorable effects produced by organic solvents dissolved in the aqueous buffer, were examined. The results are shown in Table 4. 

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