生物反应工程教学课件-Bioprocess Engineering Lesson-2.pptVIP

* 2.6.2 Electron Balance Available electrons refers to the number of electrons available for transfer to oxygen on combustion of a substrate to CO2, H2O and other small molecular weight substances, usually nitrogen-containing compounds. The number of available electrons found in organic compounds is calculated from the valence of various elements: 4 for C, 1 for H, ?2 for O, 5 for P, 6 for S, and so on. The number of available electrons for N depends on the reference state: ?3 if ammonia is the reference, 0 for molecular nitrogen N2, and 5 for nitrate. The reference state for cell growth is usually chosen to be the same as the nitrogen source in the medium. * Degree of reduction, ? , is defined as the equivalent numbers of available electrons in that quantity of material containing 1mol atom carbon. Therefore, for substrate CwHxOyNz, the number of available electrons is (4w + x ? 2y ? 3z). Thus, the degree of reduction, ?S, is (4w + x ? 2y ? 3z)/w. Electrons available for transfer to oxygen are conserved during metabolism. CwHxOyNz + aO2 + bHgOhNi cCH? O? N? + dCO2 + eH2O w?S ? 4a = c?B (2.10) * Quiz: Please calculate the degree of reduction, ?, for the compounds: 1. Ethanol C2H6O 2. Glycerol C3H8O3 3. Acetic acid C2H4O2 4. Pyruvic acid C3H4O3 5. Succinic acid C4H6O4 6. Alanine C3H7O2N 7. Lysine C6H14O2N2 The references for N are designated as NH3 and N2, respectively. * 2.6.3 Biomass Yield YB/S = (2.11) YB/S = (2.12) 2.6.4 Product Stoichiometry CwHxOyNz + aO2 + bHgOhNI cCH?O?N? + dCO2 + eH2O + f CjHk