At low dilution rates the foaminess and foam stability were low, because of
extracellular lipids excreted by the cells. This caused low protein enrichment in
the foam.
In synthetic medium and with a mean residence time of 6.5 h (dilution rate
D = 0.15 h –1 ) and 10 g l –1 glucose only 1.9 g l –1 cell mass concentration was
obtained. The flotation of this medium yielded a cell-free residue (C R * = 0.0 g l –1 )
and high cell mass concentration in the foam C S * = 81 g l –1 . The separation factor
S * was infinite. When the same medium was supplemented with a mixture of
inositol, pantothenate and pyridoxine, 4.8 g l –1 cell mass concentration was
obtained. By flotation of this medium with a 3 ml s –1 aeration rate C S * = 65 g l –1 ,
C R * = 80 mg l –1 and S * = 812 were obtained.
4.1.4
Continuous Cultivation and Flotation in Pilot Equipment
All of the investigations with cell flotation presented in the cited literature were
performed with small laboratory equipment. Gehle et al. [117] reported on the
investigation on a pilot-scale apparatus consisting of a 300-l stirred tank reactor
provided with a foam separator (Fundafoam; Chemap) and a flotation column,
3.6 m height, 10 cm internal diameter, which was directly connected to the
reactor (Fig. 7).
Hansenula polymorpha and Saccharomyces cerevisiae were cultivated on
synthetic medium with 1% glucose in fed-batch and continuous mode,
respectively, in the absence of antifoam agents. For the nutrient preparation,
sterilization and storage, 300-, 600-, 1000- and 5000-l stirred tank vessels were
used. The nutrient salt medium was sterilized without glucose. The glucose
solution was autoclaved separately and was added to the cold, sterilized
nutrient medium. The flotation column was operated in continuous mode.
Hansenula polymorpha CBS 4732 was cultivated at pH 5 and 29 °C and 37 °C,
respectively, relative aeration rates q G [(vol min –1 gas)/(medium volume)] = 0.33
and 0.50 min –1 , impeller speed N = 200–300 rpm, dilution rates D = 0.1, 0.2 and
0.3 h –1 at C-limitation, O 2 -limitation and at different phosphate concentrations,
respectively. The highest separation and enrichment factors were obtained with
D = 0.1 h –1 , 0.106 g l –1 phosphate, q G = 0.5 min –1 , at 29 °C under steady state
operation in the reactor and flotation column: C P * = 2.18 g l –1 , C R * = 0.05 g l –1 ,
C S * = 115 g l –1 , S * = 2311 and E * = 52.1, R * = 100% with 90 l h –1 gas flow rate in
the flotation column.
Cultivations of Saccharomyces cerevisiae DSM 2155 were performed at
pH 5.1, 29 °C, q G = 0.5 min –1 , N = 200–300 rpm and D = 0.1 h –1 at C-limitation
under steady state operation in the reactor and flotation column: C P * = 4.8 g l –1 ,
C R * = 0.0 g l –1 , C S * = 139.2 g l –1 , S * = ∞, E * = 29.1, R * = 100% with 180 l h –1 gas flow
rate in the flotation column.
The flotation performances in the pilot plant were better than those achieved
on a laboratory scale, probably because of the reduced wall effect in the
flotation column.
224
K. Schügerl
extracellular lipids excreted by the cells. This caused low protein enrichment in
the foam.
In synthetic medium and with a mean residence time of 6.5 h (dilution rate
D = 0.15 h –1 ) and 10 g l –1 glucose only 1.9 g l –1 cell mass concentration was
obtained. The flotation of this medium yielded a cell-free residue (C R * = 0.0 g l –1 )
and high cell mass concentration in the foam C S * = 81 g l –1 . The separation factor
S * was infinite. When the same medium was supplemented with a mixture of
inositol, pantothenate and pyridoxine, 4.8 g l –1 cell mass concentration was
obtained. By flotation of this medium with a 3 ml s –1 aeration rate C S * = 65 g l –1 ,
C R * = 80 mg l –1 and S * = 812 were obtained.
4.1.4
Continuous Cultivation and Flotation in Pilot Equipment
All of the investigations with cell flotation presented in the cited literature were
performed with small laboratory equipment. Gehle et al. [117] reported on the
investigation on a pilot-scale apparatus consisting of a 300-l stirred tank reactor
provided with a foam separator (Fundafoam; Chemap) and a flotation column,
3.6 m height, 10 cm internal diameter, which was directly connected to the
reactor (Fig. 7).
Hansenula polymorpha and Saccharomyces cerevisiae were cultivated on
synthetic medium with 1% glucose in fed-batch and continuous mode,
respectively, in the absence of antifoam agents. For the nutrient preparation,
sterilization and storage, 300-, 600-, 1000- and 5000-l stirred tank vessels were
used. The nutrient salt medium was sterilized without glucose. The glucose
solution was autoclaved separately and was added to the cold, sterilized
nutrient medium. The flotation column was operated in continuous mode.
Hansenula polymorpha CBS 4732 was cultivated at pH 5 and 29 °C and 37 °C,
respectively, relative aeration rates q G [(vol min –1 gas)/(medium volume)] = 0.33
and 0.50 min –1 , impeller speed N = 200–300 rpm, dilution rates D = 0.1, 0.2 and
0.3 h –1 at C-limitation, O 2 -limitation and at different phosphate concentrations,
respectively. The highest separation and enrichment factors were obtained with
D = 0.1 h –1 , 0.106 g l –1 phosphate, q G = 0.5 min –1 , at 29 °C under steady state
operation in the reactor and flotation column: C P * = 2.18 g l –1 , C R * = 0.05 g l –1 ,
C S * = 115 g l –1 , S * = 2311 and E * = 52.1, R * = 100% with 90 l h –1 gas flow rate in
the flotation column.
Cultivations of Saccharomyces cerevisiae DSM 2155 were performed at
pH 5.1, 29 °C, q G = 0.5 min –1 , N = 200–300 rpm and D = 0.1 h –1 at C-limitation
under steady state operation in the reactor and flotation column: C P * = 4.8 g l –1 ,
C R * = 0.0 g l –1 , C S * = 139.2 g l –1 , S * = ∞, E * = 29.1, R * = 100% with 180 l h –1 gas flow
rate in the flotation column.
The flotation performances in the pilot plant were better than those achieved
on a laboratory scale, probably because of the reduced wall effect in the
flotation column.
224
K. Schügerl