4.27 Stoichiometry of animal cell growth Analysis of the stoichiometry of animal cell growth can be complicated because of the large number of macronutrients involved (about 30 amino acids and vitamins plus other organic components and inorganic salts), and because the stoichiometry is sensitive to nutrient concentrations. Nevertheless, glucose (C6H1206) and glutamine (C5H1003N2) can be considered the main carbon sources for animal cell growth; glutamine is also the primary nitrogen source. The major metabolic by-products are lactic acid (C3H603) and ammonia (NH3). (a) A simplified stoichiometric equation for growth of hybridoma cells is: C6H12O6 + p C5H1003 N2 + O2 + r CO2 CH1.8200.84N0.25 + + C3H603 + u NH3 + v CO2 + w H2O where CH1.8200.84N0.25 represents the biomass and p, q, r, s, t, u, v, and w are stoichiometric coefficients. In a test culture, for every g of glucose consumed, 0.42 g glutamine was taken up and 0.90 g lactic acid and 0.26 g cells were produced. (i) What is the net carbon dioxide production per 100 g glucose? (ii) What is the oxygen demand? (iii) A typical animal cell culture medium contains 11 mM glucose and 2 mM glutamine. Which of these substrates is present in excess? 2. MATERIAL AND ENERGY BALANCES 136 4. MATERIAL BALANCES (iv) To prevent toxic effects on the cells, the concentrations of lactic acid and ammonia must remain below 1 g1-' and 0.07 g 1, respectively. What maximum concentrations of glucose and glutamine should be provided in the medium used for batch culture of hybridoma cells? (b) The anabolic component of the stoichiometric equation in (a) can be represented using the equation: C6H12O6 + p C5H10O3N2 +r CO2 s CH1.8200.84N0.25 (i) What proportion of the carbon in the biomass is derived from glucose, and what proportion is derived from glutamine? (ii) Considering both equations from (a) and (b), estimate the proportions of the carbon in glucose and glutamine, respectively, that are used for biomass production during culture of hybridoma cells