Constant growth phase

In a declining growth phase, the value of (j> decreases from unity to zero. When a constant growth phase is included, the value of in this phase is expressed as follows ... 

Xd is the cell concentration at the boundary of an exponential growth phase and a constant growth phase. The general equation for product formation following the Kono concept, thus, is... 

Once there is an appreciable amount of cells and they are growing very rapidly, the cell number exponentially increases. The optical cell density of a culture can then be easily detected that phase is known as the exponential growth phase. The rate of cell synthesis sharply increases the linear increase is shown in the semi-log graph with a constant slope representing a constant rate of cell population. At this stage carbon sources are utilised and products are formed. Finally, rapid utilisation of substrate and accumulation of products may lead to stationary phase where the cell density remains constant. In this phase, cell may start to die as the cell growth rate balances the death rate. It is well known that the biocatalytic activities of the cell may gradually decrease as they age, and finally autolysis may take place. The dead cells and cell metabolites in the fermentation broth may create... 

The cultures grew at 18-20°C under a constant illumination (150 pmol photons m 2-s 1) provided by cool-white fluorescence lamps. For the anaerobic induction, cells were harvested by centrifugation (5 min, 3000xg) in the exponential growth phase at an approximate culture concentration of2><106 cells ml 1 and afterwards resuspended in fresh TAP medium. 

Gates and Marlar<<0) devised a graphical procedure to determine the kinetic constants which took into account the data in the Anal stages of the growth-phase of a batch fermentation. As a result, their procedure can be used to estimate values of fim, Ks and the yield coefficient Y. The method involves rewriting equation 5.125, which is the complementary expression to the integrated form of the Monod equation 5.124, but refers to the substrate ... 

Figure 4. Preparative isoelectric focusing in a granulated gel of a desalted lyophilized culture filtrate (50 mg protein) from the late exponential growth phase of Thermoactinomyces sp. Separation carried out for 48 hr at a constant power of 8 W (29). (C>) CM-cellulase activity (A) Avicelase activity (6).

Exponential growth phase The cell number increases exponentially as the cells start to divide. The growth rate is increasing during this phase, but the division rate which is proportional to dlnCNl/dt, is constant at its maximum value, as illustrated in Figure 6.1. 

An additional advantage of this DO control system is the possibility of having a real-time estimation of the cells respiration rate. As can be observed in Equation 1, if C is constant, the term of the transfer kLa.(Cs-C) is equivalent to the consumption Q02 X. With the actuation value of the controller, the transfer rate can be calculated, and also the consumption at each moment (Kamen et al., 1996). There are several reports in the literature dealing with the use of respiration measurements to estimate cell concentration online, based on the assumption that, during the growth phase, each cell consumes a constant amount of oxygen (Yoon and Konstantinov, 1994 Ruffieux et al., 1998 Jorjani and Ozturk, 1999). 

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