where Cr is the concentration of a compound in the recirculated solution and Cp its
concentration in the permeate solution. This coefficient quantifies the membrane capacity
to retain a component of the reaction system, namely protein, substrates or products.
To determine the behavior of the membrane in the presence of enzyme and other
components of the system including substrates and products, transmission experiments
must be carried out, in the presence and absence of protein and of substrates and
products.
Membrane resistanceBy knowing that, Rmemb=1/Lp, the membrane resistance in the absence of protein (Rmemb)
can be calculated from Eq. 16:
(23)
Taking into account the resistance model, which considers the filtration flux controlled
by several hydraulic resistances,
(24)
it is possible to calculate the resistance yielded by the protein, Rprot, as:
(25)
Protein adsorption with ultrafiltration flux decline has been reported (Carvalho et al.,
2000b; Kulkarni et al., 1992) (see Figure 7.4), being pointed out that the reduction in
permeate flux is more pronounced near the protein isoelectric point (pI). Malmsten
(1998) explained the role of protein charge as a driving force for adsorption, in relation to
solvency effects, and also to the larger structural alterations verified in proteins well
above or well below the pI. The decrease in protein net charge makes the protein-solvent
interactions less favorable, which favors adsorption.
Figure 7.4 shows the evolution of permeate flow rate in different transmission
experiments reported by Carvalho et al. (2000b). It can be observed that when using the
reversed micellar system together with substrates and products, the permeate flow rate
maintains its initial
Reversed micellar bioreaction systems 213