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PTT 203 Biochemical Engineering. STOICHIOMETRY OF MICROBIAL GROWTH AND PRODUCT FORMATION. WEEK 13 By : MADAM NOORULNAJWA DIYANA YAACOB. Lets Try.
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PTT 203 Biochemical Engineering STOICHIOMETRY OF MICROBIAL GROWTH AND PRODUCT FORMATION WEEK 13 By: MADAM NOORULNAJWA DIYANA YAACOB
Lets Try • Assume that experimental measurement for certain organisms have shown that cells can convert two-thirds (wt/wt) of the substrate carbon (alkane or glucose) to biomass a) Calculate the stoichiometric coefficients for the following biological reactions: • Hexadane: C16H34 + aO2 + bNH3 c (C 4.4 H 7.3 N 0.86 O 1.2) + dH2O + eCO2 • Glucose: C6H12O6 + aO2 + bNH3 c (C 4.4 H 7.3 N 0.86 O 1.2) + dH2O + eCO2 b) Calculate the yielscoeeficientsYx/s (g dw cell/g substrate), Yx/o2 (g dwcwll/ g O2)
7.4 Theoretical Predictions of Yield Coefficient • In aerobic fermentation, the growth yield per available electron in oxygen molecules is approximately 3.14 gdw/electron when ammonia is used as the nitrogen sources. • The number of available electron per oxygen molecule is four. • When the number of oxygen molecules per mole of substrate is known, the growth yield coefficient Yx/s can easily be calculated
Consider the aerobic catabolism of glucose: C6H12O6 + 6O2 6 CO2 + 6 H2O • The total number of available electrons in 1 mole glucose is 24. • The cellular yield per available electron is Yx/s = 24 (3.14)= 76gdw cell/mol • The predicted growth yield coefficient is Yx/s= 76/180= 0.4 gdw cell/g glucose
The ATP yield (Y x/ATP ) in many anaerobic fermentation is approximately 10.5 gdw cells/ mol ATP. In aerobic fermentation this yield varies between 6-29. • When the energy yield of metabolic pathway is known (N moles of AT produced per gram of substrate consumed), the growth yield Yx/s can be calculated using the following equation • Y x/s = Y x/ATP N
Do it Yourself • Example 7.2