Cell Growth and Division

The cell growth and division typical of mammalian cells is shown schematically in Figure 9-19. The four phases of cell division are called G1, S, G2, and M, and are also described in Figure 9-19.

Figure 9-19. Phases of cell division.

In general, the growth of an aerobic organism follows the equation

9-49

A more abbreviated form of Equation (9-49) generally used is that a substrate in the presence of cells produces more cells plus product, i.e.,

9-50

The products in Equation (9-50) include CO₂, water, proteins, and other species specific to the particular reaction. An excellent discussion of the stoichiometry (atom and mole balances) of Equation (9-49) can be found in Shuler and Kargi,¹⁷ Bailey and Ollis,¹⁸ and Blanch and Clark.¹⁹ The substrate culture medium contains all the nutrients (carbon, nitrogen, etc.) along with other chemicals necessary for growth. Because, as we will soon see, the rate of this reaction is proportional to the cell concentration, the reaction is autocatalytic. A rough schematic of a simple batch biochemical reactor and the growth of two types of microorganisms, cocci (i.e., spherical) bacteria and yeast, is shown in Figure 9-20.

Figure 9-20. Batch bioreactor.