of the surface-denaturated protein into a coagulum largely devoid of surface
activity (coagulation). The polar groups in the protein cause the molecules to
spread and denature at the interface, the hydrophobic groups of the molecule
keep the film coherent. The foam stability is mainly caused by the film cohesion
and film elasticity [4]. Since only the surface-denaturated protein is effective in
stabilizing the foam, and only this protein is able to reduce the surface tension
of the medium, the rate of the complex adsorption process can be evaluated by
means of surface tension measurements.
2.1.1
Definition of Foaminess
The foam capacity of the surfactant or protein solution is characterized by the
foaminess. The foaminess S is defined as:
V S
S = 5
(1)
V tG
where V s is the equilibrium volume of the foam above the liquid layer and V tg is
the volumetric gas flow rate.
The foaminess S is an unequivocal function of the time t DG which is needed
to obtain equilibrium surface tension. e.g. S =1.85 ¥10 5 ¥1.00 –tDG for BSA
foams [5]. The area requirement of a single surface adsorbed molecule was
obtained from ds/dc, where c is the protein concentration, by the Gibbs
relationship. By assuming the existence of a hydrate ion complex, which consists
of protein and water molecules, the coordination numbers were estimated. By
applying the phase change model from ref [6] for the adsorption and surface
denaturation of BSA, a simple relationship was found between the dimensionless surface tension y and the time t:
1
ln 71 = bt n
(2)
1 – y
where
(s 0 – s se )
y = 05
(2a)
(s 0 – s st )
where s 0 is the surface tension of the pure solvent, s st is the surface tension of
the surfactant solution at time t, s se is the equilibrium surface tension, and n
and b are constants. The unequivocal relationship between S and n, as well as
between S and nb, indicate the applicability of this model.
The same relationships hold true for other proteins, such as bacterium
protease and amyloglucosidase, only the constants n and b are different [7].
Recovery of Proteins and Microorganisms from Cultivation Media by Foam Flotation
195
activity (coagulation). The polar groups in the protein cause the molecules to
spread and denature at the interface, the hydrophobic groups of the molecule
keep the film coherent. The foam stability is mainly caused by the film cohesion
and film elasticity [4]. Since only the surface-denaturated protein is effective in
stabilizing the foam, and only this protein is able to reduce the surface tension
of the medium, the rate of the complex adsorption process can be evaluated by
means of surface tension measurements.
2.1.1
Definition of Foaminess
The foam capacity of the surfactant or protein solution is characterized by the
foaminess. The foaminess S is defined as:
V S
S = 5
(1)
V tG
where V s is the equilibrium volume of the foam above the liquid layer and V tg is
the volumetric gas flow rate.
The foaminess S is an unequivocal function of the time t DG which is needed
to obtain equilibrium surface tension. e.g. S =1.85 ¥10 5 ¥1.00 –tDG for BSA
foams [5]. The area requirement of a single surface adsorbed molecule was
obtained from ds/dc, where c is the protein concentration, by the Gibbs
relationship. By assuming the existence of a hydrate ion complex, which consists
of protein and water molecules, the coordination numbers were estimated. By
applying the phase change model from ref [6] for the adsorption and surface
denaturation of BSA, a simple relationship was found between the dimensionless surface tension y and the time t:
1
ln 71 = bt n
(2)
1 – y
where
(s 0 – s se )
y = 05
(2a)
(s 0 – s st )
where s 0 is the surface tension of the pure solvent, s st is the surface tension of
the surfactant solution at time t, s se is the equilibrium surface tension, and n
and b are constants. The unequivocal relationship between S and n, as well as
between S and nb, indicate the applicability of this model.
The same relationships hold true for other proteins, such as bacterium
protease and amyloglucosidase, only the constants n and b are different [7].
Recovery of Proteins and Microorganisms from Cultivation Media by Foam Flotation
195