foam liquid C S * = 120 g l –1 in continuous operation and 40 g l –1 in batch operation mode. The enrichment E * and separation S * are higher in continuous
operation as well.
In general C S * diminishes with increasing cell concentration. Factors which
increase foaminess diminish C S * and thus E S * and S R * too. Systematic investigations dealt with the influence of (i) the cultivation conditions, and (ii) the
flotation equipment, construction and operational parameters.
4.1.2
Influence of Cultivation Conditions
The medium feed rate (10 ml min –1 ), the gas feed rate (1 ml s –1) of the flotation
and the temperature (37 °C) and pH (5.0) of the cultivation were kept constant.
The investigations indicated that the cell separation factor S * is independent
of:
– the growth phase (exponential, transient or stationary),
– the presence of low amounts of Ca 2+ ions,
– pH value close to pH 5.0,
– cultivation temperature (close to the optimum),
– presence of a low amount of substrate, and
– growth limitation by O 2 .
C S is diminished with increasing age of the cells (after sampling) [113].
Typical flotation performances of Hansenula polymorpha cells from C-, Nand P-limited cultivations are shown in Table 6. The highest separation was obtained with cells cultivated under P-limitation (with 4 ¥ 25 ¥ 10 –3 g P/g cell
mass): S * = 442 and R * = 96.4 [116].
The cultivation medium composition and the proteins excreted by the yeast
cells were determined and their influence on the flotation performance was
investigated by Bahr et al. [115]. The sodium dodecyl sulfate polyacrylamide gel
electrophoresis (SDS-PAAGE) and native PAAGE measurements indicated that
during the cultivation various glycoproteins were excreted, which were
distributed differently between the foam and the flotation residue liquid. A
222
K. Schügerl
Table 6. Typical flotation performances of the Hansenula polymorpha cells from C-, N- and Plimited cultures as well as C-limited cultures with amino acid supplement C(AS) in the
dilution range 0.1 and 0.25 h –1 (1 Pirt unit = 0.0255 g P/g cell mass) [116]
Limitation
D (h –1 )
C* P (g l –1 )
C* R (g l –1 )
C* S (g l –1 )
R*(%)
S*
C
0.105
4.98
4.34
28.8
12.9
6.63
C(AS)
0.11
5.64
4.34
43.5
23.0
10.0
N
0.12
5.15
2.72
52.6
47.2
19.34
P (0.33 Pirt)
0.10
4.47
0.40
75.0
91.0
187.5
C
0.225
5.2
2.73
68.3
47.5
25.0
C(AS)
0.227
5.6
1.31
64.5
76.6
49.23
P (0.166 Pirt)
0.25
4.18
0.15
66.4
96.4
442.6
operation as well.
In general C S * diminishes with increasing cell concentration. Factors which
increase foaminess diminish C S * and thus E S * and S R * too. Systematic investigations dealt with the influence of (i) the cultivation conditions, and (ii) the
flotation equipment, construction and operational parameters.
4.1.2
Influence of Cultivation Conditions
The medium feed rate (10 ml min –1 ), the gas feed rate (1 ml s –1) of the flotation
and the temperature (37 °C) and pH (5.0) of the cultivation were kept constant.
The investigations indicated that the cell separation factor S * is independent
of:
– the growth phase (exponential, transient or stationary),
– the presence of low amounts of Ca 2+ ions,
– pH value close to pH 5.0,
– cultivation temperature (close to the optimum),
– presence of a low amount of substrate, and
– growth limitation by O 2 .
C S is diminished with increasing age of the cells (after sampling) [113].
Typical flotation performances of Hansenula polymorpha cells from C-, Nand P-limited cultivations are shown in Table 6. The highest separation was obtained with cells cultivated under P-limitation (with 4 ¥ 25 ¥ 10 –3 g P/g cell
mass): S * = 442 and R * = 96.4 [116].
The cultivation medium composition and the proteins excreted by the yeast
cells were determined and their influence on the flotation performance was
investigated by Bahr et al. [115]. The sodium dodecyl sulfate polyacrylamide gel
electrophoresis (SDS-PAAGE) and native PAAGE measurements indicated that
during the cultivation various glycoproteins were excreted, which were
distributed differently between the foam and the flotation residue liquid. A
222
K. Schügerl
Table 6. Typical flotation performances of the Hansenula polymorpha cells from C-, N- and Plimited cultures as well as C-limited cultures with amino acid supplement C(AS) in the
dilution range 0.1 and 0.25 h –1 (1 Pirt unit = 0.0255 g P/g cell mass) [116]
Limitation
D (h –1 )
C* P (g l –1 )
C* R (g l –1 )
C* S (g l –1 )
R*(%)
S*
C
0.105
4.98
4.34
28.8
12.9
6.63
C(AS)
0.11
5.64
4.34
43.5
23.0
10.0
N
0.12
5.15
2.72
52.6
47.2
19.34
P (0.33 Pirt)
0.10
4.47
0.40
75.0
91.0
187.5
C
0.225
5.2
2.73
68.3
47.5
25.0
C(AS)
0.227
5.6
1.31
64.5
76.6
49.23
P (0.166 Pirt)
0.25
4.18
0.15
66.4
96.4
442.6