62
Chapter 3
Table 3.3 Elemental composition and degree of reduction of typical compounds encountered in
fermentation processes.
Compound
Formula
Degree of
reduction per
carbon, v
Com pound
Formula
Degree of
reduction per
carbon, k-
Formic acid
C H A
2
Alanine
C A N O ,
4
Acetic acid
C A O ,
4
Arginine
C$H|
4
N
4
0 ,
3.67
Propionic acid
C3H A
4.67
Aspargine
C A N A
3
Butyric acid
C
4
H A
5.00
Aspartate
c
4
h tn 04
3
Valeric acid
C jH iA
5.20
Cysteine
C
3
H A N S
6
Palmitic acid
CkA A
5.75
Glutamate
C A N Ö
4
3.60
Lactic acid
C A O ,
4
Glutamine
C A o N A
3.60
Gluconic acid
C&H1307
3.67
Glycine
C A N O ,
3
Pyruvic acid
C A O ,
3.33
Leucine
C
6
H„NO,
5
Oxalic acid
C
2
H
2
0*
1
Isoleucine
C
6
H
13
NO,
5
Succinic acid
c a o *
3.50
Lysine
c
6
h 14n a
4.67
Fumaric acid
C
4
H
404
3
Histidine
C A N
3
O,
3.33
Malic acid
C
4
H A
3
Phenylalanine
C,H„NO,
4.44
Citric acid
C
6
H*0
7
3
Proline
C A N O ,
4.40
Hexoses
C6H iA
4
Serine
C A N O ,
3.33
Disaccharides
C t A A
1
4
Threonine
C A N O ,
4
Methane
CH
4
8
Tryptophane
C|,H12N A
4.18
Ethane
C A
7
Tyrosine
C A ,N Ö ,
4.22
Propane
c,H,
6.67
Valine
CjH „N O ,
4.80
Methanol
CH
40
6
Methionine
C
5
H„0,NS
6
Ethanol
C A O
6
Urea
c h
4
o n
2
6
iro-Propanol
C,H80
6
n-Butanol
C
4
H
10
O
6
Glycerol
C A O ,
4.67
Acetone
C A O
5.33
Formaldehyde
CH,0
4
Acetaldehvde
C,FLO
5
When the degree of reduction h&s been determined for all reactants and products in a
stoichiometric equation it is possible to redox balance any of the metabolic pathways illustrated
in Chapter 2. Table 3.4 shows some typical examples of pathway reactions. In some pathways
C02 is split off by decarboxylation of a carboxylic acid. This has to be recognized by inspection
of pathway diagrams in order to write the correct stoichiometry for the pathway reaction.
Whereas the production or consumption of redox co-factors can be calculated from a redox
balance the free energy yield associated with the reaction (in units of ATP) has to be looked up in
pathway diagrams. Table 3.4 also specifies the ATP yield associated with the overall reactions.
Except for a few overall reactions such as the conversion of glucose to lactate or to ethanol a
redox carrying co-factor is either generated or consumed. Pathways that produce redox units
must therefore balance pathways that consume redox units in order that the net production of
redox units is zero in the steady state operation of the cell. This is going to be the foundation of
metabolite balancing to be introduced in Chapter 5.
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