Growth Microbial kinetics, Product

V. L. Yarovenko Theory and Practice of Continuous Cultivation of Microorganisms in Industrial Alcoholic Processes. - Y. Miura Mechanism of Liquid Hydrocarbon Uptake by Microorganisms and Growth Kinetics. -J. E. Zajic, N. Kosaric, J. D. Brosseau Microbial Production of Hydrogen. - T.Enatsu, AShin-myo In vitro Synthesis of Enzymes. Physiological Aspects of Microbial Enzyme Production. 

Non-stirred, aerated vessels are used in the process for traditional products such as wine, beer and cheese production. Most of the newly found bioprocesses require microbial growth in an aerated and agitated system. The percentage distribution of aerated and stirred vessels for bioreactor applications is shown in Table 6.1. The performances of various bioreactor systems are compared in Table 6.2. Since these processes are kinetically controlled, transport phenomena are of minor importance. 

From kinetics studies of unicellular organisms, a set of mathematical expressions have been established to represent the most frequent phenomena in bioprocesses. These phenomena involve a limitation or inhibition of growth and product formation, caused by the presence of substrates, products, or byproducts in culture media. Many of these expressions do not derive from known kinetic mechanisms. In fact, they are simply mathematical expressions with fitted parameters that are able to reproduce experimentally observed kinetic profiles. These equations have been derived and used in many unstructured microbial or cell models. 

Shaughnessy TS Kargi F (1990a) Growth and product inhibition kinetics of T-cell hybridomas producing lymphokines in batch and continuous culture. Enzyme and Microbial Technology 12 669-675. 

To choose the adequate bioreactor design for continuous PHA production, kinetics for both biomass and PHA production by the microbial strain should be considered. In the case of PHA production directly associated with microbial growth as it is found in Alcaligenes latus DSM 1122 on sucrose [128], or for Pseudomonasputida ATCC 29147 on fatty acids [97,98], a one-step continuous process using a continuous stirred tank reactor (CSTR) is a viable solution. 

Data about the physical characteristics of a bioreactor can provide only limited information. The complete characterization of a bioreactor requires additional studies involving biological test systems ( reference fermentations ). The fluid dynamics and rheological behavior of media are both directly and indirectly influenced by the presence of biological cells (Fiechter, 1978). Microbial processes whose growth or production kinetics are specifically dependent on changes in their medium or the reactor come into consideration as biological test systems (Karrer, 1978). Because of the central role of mass... 

Microbial activities like growth and product formations can be regarded as a sequence of enzymatic reactions. On this basis Ferret (1960) constructed a kinetic model for a growing bacterial cell population. The main pathways for major nutrients are considered together with pathways for minor nutrients and trace elements linked to each other. This metabolic network can be simplified with the aid of the concept of the rate-determining step (rds), resulting in a master reaction or bottleneck that limits the total flux and the rate of the process. 

Figure 5.34. Possible hypotheses for the effect of product concentration p on microbial growth rate p linear decrease (1), first-order decrease (la), sudden stop (3), and decrease after a period of no effect (2,2a). (Hinshelwood, The Chem. Kinetics of the Bacteria Cell, 1946, Oxford University Press.)...

Figure 5.52. Conceptual representations of the interactive model, (a) is converted to Pi by an enzyme that requires S2 as a cofactor, (b) Substrates and S2 from two parallel pathways are combined by enzyme to produce a product P that is required for growth, (c) Plots of lines of constant dimensionless specific growth rate p/Prmx as a function of two dimensionless substrate concentrations for interactive models of the Megee type (cf. Equ. 5.169) with Monod kinetics (Reprinted with permission from In Microbial Population Dynamics, Bader, 1982. Copyright CRC Press, Inc., Boca Raton, FL.)...

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