Product formation kinetics

Product formation kinetics in mammalian cells has been studied extensively for hybridomas. Most monoclonal antibodies are produced at an enhanced rate during the Gq phase of the cell cycle (8—10). A model for antibody production based on this cell cycle dependence and traditional Monod kinetics for cell growth has been proposed (11). However, it is not clear if this cell cycle dependence carries over to recombinant CHO cells. In fact it has been reported that dihydrofolate reductase, the gene for which is co-amplified with the gene for the recombinant protein in CHO cells, synthesis is associated with the S phase of the cell cycle (12). Hence it is possible that the product formation kinetics in recombinant CHO cells is different from that of hybridomas. 

The relative rates of reaction of the nucleic acid bases with heavy transition metal ions at neutral pH are in the same order as the relative nucleophilicites of the bases, that is G > A > C > U or T. This order parallels the relative rates of reactions for cA-[(NH3)2Pt(OH2)2] (see Figure 9), while the equilibrium constants for the same reactions are very close in magnitude. In contrast, HsCHgOH, which is more labile to substitution, nndergoes more favorable binding with deprotonation at N-3 of thymine residues in nucleic acids. Thus the relative facilities of individual reactions can lead to differences in initial product formation (kinetic control). Subsequent changes in the metal-nucleic acid complexes can be nnder kinetic or thermodynamic control. 

Enzyme production kinetics in SSF have the potential to be quite complex, with complex patterns of induction and repression resulting from the multisubstrate environment. As a result, no mechanistic model of enzyme production in SSF has yet been proposed. Ramesh et al. [120] modeled the production of a-amylase and neutral protease by Bacillus licheniformis in an SSF system. They showed that production profiles of the two enzymes could be described by the logistic equation. However, although they claimed to derive the logistic equation from first principles, the derivation was based on a questionable initial assumption about the form of the equation describing product formation kinetics They did not justify why the rate of enzyme production should be independent of biomass concentration but directly proportional to the multiple of the enzyme concentration and the substrate concentration. As a result their equation must be considered as simply empirical. 

Lehr F, MorweiserM, RoseUo Sastre R, Kruse O, Posten C Process development for hydrogen production with Chlamydomonas reinhardtii based on growth and product formation kinetics, J Biotechnol 162 89—96, 2012. 

Another generalization of product-formation kinetics based on mechanistic background but still using the formal kinetic approach has been presented by Bajpaj and Reuss (1980a, 1981). This model, (cf. App. II) along with rate equations for ju, %, and Qq, was successfully used to simulate experimental data. The concept of this model approach is to eliminate S between the equations for [x (see Equ. 5.38) and for qp (see Equ. 5.106). The result is an equation relating with in a more structured manner ... 

Substituting the logistic form of product formation kinetics (see Equ. 5.122) for qp gives... 

The addition of Co and Mn acetates to the reaction mixture changes the general features of the products formation kinetics (1.19). Thus increases and acetophenone has been identified (AcP). The sum of the products exceeds by 7.3-fold that at cumene ozonolysis. OZ is obtained at the interaction of ozone with the benzene ring, and AcP is provided by the monomolecular decomposition reaction of RO"-radicals. Most likely the main role of Mn is in accelerating of these two reactions. The catalytic properties of the metal salts studied are confirmed by the ratio of the amount of the products formed in the catalyzed and noncatalysed processes per unit of absorbed ozone. At Co Mn=5 l this ratio becomes equal to 7.3 and is greater by about 6% than that in the absence of Mn. The cumene conversion is increased but the selectivity of the process is reduced. The contribution of OZ and ApC to the total sum of the products formed is 27%. The synergism of the simultaneous action of the both salts (Fig. 19) can be associated with the occurrence of the following reaction ... 

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