Figure 7.2 General representation of a
reverse micelle identifying the
partitioning (P 1 , P 2 and P 3 ) adsorption
(Kad) and diffusion (Kdif) processes.
(10)
Sw is obtained through the resolution of the second order equation:
(11)Similarly Sorg, Saot,f and Saot,ads are obtained respectively, from:
(12)(13)
(14)
By applying the partition coefficients and the adsorption constants referred above, the
concentrations of hexanol in the isooctane phase (Sorg), in the aqueous phase (Sw) and in
the AOT, either adsorbed (Saot,ads) or free (Saot,f) were calculated.
The analysis of different hypotheses enabled a point to be reached where the effective
substrate concentrations coincide with the kinetic concentrations of substrate calculated
through the effectiveness coefficients. In fact, considering KH=0.0177 mol−^1 .ml, when
qmax=0.75, the estimation of effective substrate is very precise for the lower substrate
concentrations (see Table 7.2) (Carvalho et al., 2000a).
The model accurately estimates the effective substrate concentrations below the
kinetic control. Above 300 mM hexanol, the SefMM differs from Sef due to the diffusion
process. Diffusion does not control the process, but instead permits the rapid entry of
substrate to replace the consumed molecules in the vicinity of the biocatalyst. Application
of the model to calculate effective concentrations led to a linear relation between the
hexanol accessed by cutinase and its thermostability (correlation coefficient (R) was
0.994) (Carvalho et al., 2000a).
The model identifies the micellar variables integrating the experimental data to predict
consistent distribution values. A major point of the model is to stress the particular
Reversed micellar bioreaction systems 207