PEG, a poly(dimethylsiloxane) AFA (JT Baker, USA) was used, which increased
the death rate.
3
Protein Flotation
Flotation has been used for centuries in the mining industry for the dressing
and concentration of mineral ores and in waste water engineering. Despite
many publications and several books on the use of flotation in the industry,
only a few papers and short chapters in books have dealt with the application
of flotation for protein and cell recovery [57, 58]. The theory of flotation has
been discussed by Schulze [59] and Loewenberg and Davis [60]. Some biotechnological applications of flotation were presented in the handbook written
by Rousseau [61].
The recovery of proteins from cultivation medium is usually performed by
precipitation, adsorption, flocculation, extraction and ultrafiltration [62–64].
The adsorptive bubble separation techniques were considered in a book by
Lemlich [65]. Foam flotation was described by Wilson and Clark [66]. However,
in these books, no systematic investigations on the influence of equipment and
operating parameters on protein enrichment and separation factors were
published.
Foam flotation is especially suitable for protein recovery from aqueous
solutions at low protein concentrations. BSA was used as a model protein in
batch [67] and continuous operation [68–71]. b-Casein recovery [72] and
binary mixtures (BSA/lysozyme, b-casein/lysozyme and b-casein/BSA) and
their separation were also investigated [73].
The most common mode of operation of foam fractionation employed by
various investigators is the single stage semibatch flotation: the protein solution
used in batch mode and aerated continuously [71]. However, continuous
multistage operation has the highest performance [70]. Therefore, this operation mode is discussed in detail.
3.1
Continuous Flotation of Proteins
Typical continuous laboratory flotation equipment has been described by Gehle
and Schügerl [70], who investigated the recovery of BSA from aqueous solution
by foam flotation. The thermostatted flotation setup consisted of a column with
a 23-mm internal diameter, 49-cm bubbling liquid height and 30-cm foam layer
height. Nitrogen gas saturated with water was distributed by perforated and
porous plates, respectively. The protein solution was fed into the column at the
height of the interface between the bubble column and the foam column. The
interface was controlled by an overflow. The foam left the column at the top. The
foam liquid was recovered by a mechanical foam breaker. The remaining liquid
at the bottom was disposed of through the overflow (Fig. 5). Another thermostatted setup consisted of a column 25 mm in diameter, 44 cm bubbling
liquid height and 18 cm foam layer height operated in the same way as the other
212
K. Schügerl
the death rate.
3
Protein Flotation
Flotation has been used for centuries in the mining industry for the dressing
and concentration of mineral ores and in waste water engineering. Despite
many publications and several books on the use of flotation in the industry,
only a few papers and short chapters in books have dealt with the application
of flotation for protein and cell recovery [57, 58]. The theory of flotation has
been discussed by Schulze [59] and Loewenberg and Davis [60]. Some biotechnological applications of flotation were presented in the handbook written
by Rousseau [61].
The recovery of proteins from cultivation medium is usually performed by
precipitation, adsorption, flocculation, extraction and ultrafiltration [62–64].
The adsorptive bubble separation techniques were considered in a book by
Lemlich [65]. Foam flotation was described by Wilson and Clark [66]. However,
in these books, no systematic investigations on the influence of equipment and
operating parameters on protein enrichment and separation factors were
published.
Foam flotation is especially suitable for protein recovery from aqueous
solutions at low protein concentrations. BSA was used as a model protein in
batch [67] and continuous operation [68–71]. b-Casein recovery [72] and
binary mixtures (BSA/lysozyme, b-casein/lysozyme and b-casein/BSA) and
their separation were also investigated [73].
The most common mode of operation of foam fractionation employed by
various investigators is the single stage semibatch flotation: the protein solution
used in batch mode and aerated continuously [71]. However, continuous
multistage operation has the highest performance [70]. Therefore, this operation mode is discussed in detail.
3.1
Continuous Flotation of Proteins
Typical continuous laboratory flotation equipment has been described by Gehle
and Schügerl [70], who investigated the recovery of BSA from aqueous solution
by foam flotation. The thermostatted flotation setup consisted of a column with
a 23-mm internal diameter, 49-cm bubbling liquid height and 30-cm foam layer
height. Nitrogen gas saturated with water was distributed by perforated and
porous plates, respectively. The protein solution was fed into the column at the
height of the interface between the bubble column and the foam column. The
interface was controlled by an overflow. The foam left the column at the top. The
foam liquid was recovered by a mechanical foam breaker. The remaining liquid
at the bottom was disposed of through the overflow (Fig. 5). Another thermostatted setup consisted of a column 25 mm in diameter, 44 cm bubbling
liquid height and 18 cm foam layer height operated in the same way as the other
212
K. Schügerl