1 / 21

Engineering of Biological Processes Lecture 3: Yields and stoichiometry

Engineering of Biological Processes Lecture 3: Yields and stoichiometry. Mark Riley, Associate Professor Department of Ag and Biosystems Engineering The University of Arizona, Tucson, AZ 2007. Objectives: Lecture 3. Biosynthetic processes (anabolic) Case studies - cholesterol

Download Presentation

Engineering of Biological Processes Lecture 3: Yields and stoichiometry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Engineering of Biological ProcessesLecture 3: Yields and stoichiometry Mark Riley, Associate Professor Department of Ag and Biosystems Engineering The University of Arizona, Tucson, AZ 2007

  2. Objectives: Lecture 3 • Biosynthetic processes (anabolic) • Case studies - cholesterol • Stoichiometry and modeling cellular requirements • "You are what you eat"

  3. Stoichiometry • Provides information on fundamental constraints • Substrate conversion to product • Cell mass from substrate

  4. Yields and yield coefficients • Mass based = “kg” of this from “kg” of that • Y (output / input) • Y x/s • Y p/s • Y ATP/O2 • Ymx/s maximal yield of cell mass from substrate

  5. YIELD Yield • Overall • Instantaneous • Ratio of rates • Ratio of yields • Theoretical = Y • Observed = Y’

  6. Cell metabolism • Y’ lactate / glucose = ranges from 2 to 0 based on environment • The basic reaction is: • Glucose + 2 Pi + 2 ADP → 2 Lactate + 2 ATP + 2 H2O

  7. Bacterial dry cell weight [mg/L] Slope = dX/dS 7 (mg/L) / (g/L) Glucose [g/L] • Yield of cell mass from substrate • Y x/s

  8. Aerobic Yx/s=58 mg/mol Bacterial dry cell weight [g/L] Anaerobic Yx/s=22 mg/mol Glucose [mM]

  9. Cell composition CHxOyNz

  10. In a very simplistic interpretation of metabolism, the following applies: • Cells + medium + O2 (sometimes) → more cells + product + CO2 + H2O • Medium contains sugars, amino acids, cofactors and the elements in the previous table.

  11. Stoichiometric calculations • Based on 1 mole of C in the input • CHmOn + a O2 + b NH3→ • c CHaObNd + dH2O + eCO2 • This is normalized to 1 mole of C. Could also be normalized to 1 mole of the C source compound • Perform elemental balances to determine the unknown values of the cofactors

  12. Example • C6H12O6 + a O2 + b NH3→ • c C4.4H7.3O1.2N0.86 + dH2O + eCO2 • 2/3 of the glucose C goes to biomass • What are the stoichiometric coefficients, and Yx/s, Yx/O2? MWglucose = 180 MWcell = 89.62 MWoxygen = 32 MWammonia = 17

  13. Generalized growth reaction • C6H12O6 + a NH3 + b O2→a CH1.8O0.5N0.2 + • b CHxOyNz + gCO2 + dH2O • Normalized to 1 mole of carbon source compound • Where a, b, a, b, g, d, x, y, z depend on the type of cell involved. • a, b, a, b, g, d, are stoichiometric coefficients • When little info is available about cell composition, use an approximated cell composition of CH1.8O0.5N0.2 • This yields a MW of a cell ~ 24.6

  14. Generalized growth reaction C6H12O6 + a NH3 + b O2 → a CH1.8O0.5N0.2 + b CHxOyNz + gCO2 + dH2O g of cells from g of glucose

  15. Lack of information • Unfortunately, the elemental balances often do not provide enough information to completely solve for the stoichiometric coefficients.

  16. Respiratory quotient • RQ = YCO2/O2 • Molar basis • Moles of CO2 produced from moles of O2 • Provides information on the metabolic state of the cell • A high RQ means that much CO2 is produced and hence the metabolism is operating at high efficiency

  17. Aerobic metabolism • CHmOn + a O2 + b NH3→ • c CHaObNd + d CHxOyNz + eH2O + fCO2 • RQ = ?

  18. Degree of reduction • Electron balance • = # of available electrons / g of atomic C • Or, this can be described as: • = # of available electrons / # of C’s • Provides another independent equation

  19. C = 4 H = 1 N = -3 O = -2 P = 5 S = 6 CO2 = +4 (C) + -2 (O) = 0 C6H12O6 = 6(4) + 12(1) + 6(-2) = 24 g = 24 / 6 (# carbon atoms) = 4 C2H5OH = 2(4) + 6(1) + (-2) = 12 g = 12 / 2 (# carbon atoms) = 6 Degree of reduction

  20. Example – yeast grown on glucose • C6H12O6 + 0.48 NH3 + 3 O2→ • 0.48 CH1.8O0.5N0.2 + 3.12CO2 + 4.32H2O • To grow yeast to 50 g/L in a 100,000 L reactor, determine: • a) mass of glucose and ammonia required • b) O2 required • c) Yx/s and YX/O2 MWglucose = 180 MWcell = 24.6 MWoxygen = 32 MWammonia = 17

  21. HW #1 questions • What kind of cell would you use to produce androstenedione? Your answer should describe the attributes of such a cell (don't just state, "a cell that produces andro"). An answer longer than 4 sentences is too much. • Producing cholesterol is an energy intensive process. How much energy (in terms of # of ATP molecules) is consumed in producing one cholesterol molecule from a source of glucose?

More Related