Environmental Engineering Reference
In-Depth Information
TABLE 13.4 Calculated material streams (kg.s
-1
) for the fermentation of Figure 13.5
(where the smallest stream, “fermentation additives,” has been left out for simplicity)
Fermentation
additives
Recycled
yeast
Unclarified
wine
Fermentation
vapor
Component
Juice in
Acetic acid
0.00160
0.17153
Yeast
4.86066
5.18276
CO
2
0.00842
0.12458
9.81202
Ethanol
0.27260
10.21233
0.12587
Glucose/fructose
2.24468
0.00255
0.27432
Glycerol
0.00548
0.58929
Impurity
0.58625
0.00525
0.56369
Isoamyl alcohol
0.00144
0.15510
Minerals
0.06240
0.00059
0.06299
Succinic acid
0.00039
0.04184
Sucrose
18.32557
H
2
SO
4
0.00110
0.00110
H
+
0.00004
0.00406
Antifoam
0.09728
0.00091
0.09820
Disperging agent
0.02594
0.00024
0.02619
Soda
0.11804
0.00111
0.11914
Water
70.19729
43.80449
112.94909
0.11026
Total
91.41620
0.24126
48.96687
130.57619
10.04815
The described fermentation is continuous, although batch fermentation is more
common. Here, we only consider the steady state of the continuous process. The sugars
are converted almost completely by baker
s yeast. Products besides ethanol are CO
2
,
glycerol, succinic acid (butane-1,4-diacid), isoamyl alcohol (3-methyl-1-butanol), and
more yeast.
During fermentation, sucrose is first hydrolyzed into
D
-glucose and
D
-fructose by
an extracellular enzyme:
'
C
12
H
22
O
11
+H
2
O
!
2C
6
H
12
O
6
ð
RX
:
13
:
2
Þ
Glucose and fructose are isomeric C
6
sugars (C
6
H
12
O
6
). The C
6
sugars are taken up by
the cells. The fermentation itself runs without O
2
to prevent conversion of sugars into
H
2
O and CO
2
. Instead of liberating a large amount of chemical energy, the yeast only
liberates a small amount by formation of ethanol:
C
6
H
12
O
6
!
2C
2
H
5
OH + 2CO
2
ð
RX
:
13
:
3
Þ
Section 13.1.1 shows the complete catabolic reaction. The involved phosphate
compounds remain intracellular and do not play a role in the material balance of the
fermentation. The other compounds pass the cell membrane. Less than 2 kg m
-3
CO
2
dissolves inwater, somost escapes the solution as gas bubbles, with small amounts
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