Glucose consumption, specific rate

Optimal conditions for insect cell growth have been extensively studied, but for product expression with a baculovirus infected insect cell the focus should be on the difference in the metabolic requirements of infected vs. uninfected cells, which has been observed to differ after infection. The alanine specific production rate decreases almost four-fold, while phenylalanine specific consumption rate increase 11-fold and glutamine specific consumption decrease [65]. Both an increase [66] and a decrease [67] in glucose consumption rates of insect cells after infection have been reported. This reflects some differences in the media and vectors that were used however, it is normal to expect a higher metabolic burden after infection due to the increase in protein expression rates caused by the infection. This creates a concern about the impact of nutrient limitations on the productivity of the system. 

The specific rate of consumption of glucose Rs (grams of glucose consumed per hour per gram of cells in the fermentor) also depends on the specific growth rate /a. The most simple relation ship is a linear one ... 

Typical kinetic profiles (hybridoma). (A) Cell concentration and viability (B) glucose consumption (GLC) and lactate production (LAC) (C) monoclonal antibody production (mAb) (D) glutamine consumption (GLN) and ammonium production (NH4+) (E) specific growth rate (px) (F) alanine (ALA) and glycine (GLY) production. Adapted from Lee (2003). Symbols correspond to the experimental data and the lines to the manual curve fitting. Vertical lines indicate the instant at which exponential growth phase ended (gx < Px.max)-... 

The central parameter in cell culture is the viable cell concentration. The specific growth rate ( x), the specific death rate k and the fraction of viable cells (/ ) are used to characterize the proliferative state and health of a culture. These parameters are calculated from the viable and non-viable cell concentrations using equations appropriate for the type of culture vessel employed (see below). The viable cell concentration is also used to calculate the metabohc quotients (e.g. specific glucose consumption rate), as discussed in a later section. In the absence of cell concentration data, analysis is limited to ratios of metabolic rates (see below). 

Figure 42.7 Metabolic quotients for the glucose step change experiment described in Figure 4.2.5. (a) Specific glucose consumption rate (mmol glucose consumed viable celL da>r ) as a function of culture time, (b) Specific lactate production rate (mmol lactate produced viable celH day" ) as a function of culture time. Adapted from Miller et al (1989) by permission of Biotechnology and Bioengineering.

For most cell lines it has been found to increase linearly with the specific growth rate. Thus the specific rate of glucose uptake is often expressed as a function of x by Equation 4.3.3, which contains two parameters the non-growth-assodated specific glucose consumption rate, rriQ c (mmol glucose 1(T cells h ), and the... 

Calculate the specific rates of nutrient consumption The specific rate of glucose consumption ... 

Specific glucose consumption rate (mmol 10 cells h" )... 

MV mean value SD standard deviation Gr.A group A [pm-e silicone oil and poly(propylene glycol) PPG and silicone oil/PPG mixture] Gr.B group B (aqueous emulsion with only 10% S184) X cell mass concentration Yx/s yield coefficient of growth with respect to substrate P productivity of P-galactosidase SP specific productivity SG specific glucose consumption rate [51]... 

Figure 27. Heat flux is plotted as a function of the specific growth rate ( ) showing the monotonically decreasing relationship. This dependence extends to the fluxes for lO" x IFN-y production flux, lU s per cell, (A) and the major catabolites, 10 x glucose consumption flux, mol s per cell, ( ) and lO x glutamine consumption flux, mol s per cell (A) (Reproduced from Reference [22] with permission).

Data presented for the glucose step change in Example 2 can be used to estimate the specific ATP consumption rate as a function of the P/O ratio qQ (not shown) is calculated from Equation 4.2.36, while (Table 4.2.2) is calculated from Equation 4.2.31 as shown in Example 2. These values are then substituted into Equation 4.2.37 to obtain the values shown in Figure 4.2.8 for P/O ratios of 2 and 3. 

Figure 4.3.2 Evolution with time of the specific growth and death rates (a), the specific consumption rates of glucose (b) and glutamine (c) and the specific production rates of lactate (b), ammonia (c) and monoclonal antibodies (d) in VO 208 batch culture (data from Figure 4.3.1).

Figure 4.3.3 Relationships between specific glucose (a) and glutamine (c) consumption rates, lactate (b), ammonia (d) and monoclonal antibody (e) production rates and specific growth rate during lag and growth phases of VO 208 batch culture.

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