Biochemical Engineering Fundamentals, Part 1 - Bailey J., Ollis D. 1989

Stoichiometry and Energetics of Metabolic Transformations
Stoichiometry of Cell Growth and Product Formation

Although Cell growth is an exceedingly complex and elegant process, it naturally obeys the laws of conservation of matter. During Cellular metabolic processes, the atoms of carbon, nitrogen, hydrogen, oxygen, and other vital chemical elements discussed in Ch. 2 are rearranged, but the total amount of each of these elements incorporated into cellular structures is exactly equal to the amount taken up by The Cell from the nutrient medium. In addition, The amount of metabolite produced or heat released during cell growth is frequently proportional to the amount of substrate consumed by the cell or to the amount of another metabolic product, such as CO₂. In this section, we examine some rather strict constraints imposed on the material balance, as well as A number of useful approximate empirical stoichiometric relationships. As we will see, these stoichiometric aspects are directly relevant to biochemical engineering, where they must be taken into account when addressing A wide variety of issues ranging from nutrient medium Selection to the design of automated control systems and bioreactor cooling Methods. Furthermore, as in the analysis of any Reactor, stoichiometric relationships determine the mass balance of substances within the bioreactor and allow for the most efficient and targeted application of reaction kinetics specifics (Ch. 7).

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FIG. 5.27. Schematic diagram of metabolic pathways leading to secondary metabolites. Bold arrows highlight enzyme-catalyzed reaction sequences that yield secondary metabolites. [Reprinted with permission from: Malik V. S., Microbial Secondary METABOLISM, Trends Biochem. Sci., 5, 68 (1980).]