During the process synthesis procedures aimed at identifying those technological
configurations for fuel ethanol production with better technoeconomic and environmental
performance, the authors of this book carried out a comprehensive review of
the available models for describing ethanolic fermentation kinetics (Sánchez, 2008).
Considering that the three main types of feedstocks employed for fuel ethanol production
can be broken down into glucose, the first stage of the analysis included the
selection of the most appropriate kinetic models that take into account the growth
of S. cerevisiae or Z. mobilis on glucose-rich media. As a kind of “sample” that
evidences the great diversity of kinetic models studied, some kinetic relationships
for cell growth rate are shown in Table 7.4. In this table, substrate consumption
and product formation rates are not shown by space limitations, but these expressions
depend, in turn, on either cell growth rate or cell concentration. All the presented
models consider the substrate limitation, which is mostly expressed through
Monod-type equations (Monod, 1949). Similarly, all the models include expressions
describing the growth rate inhibition by the ethanol formed. One of the most useful
models corresponds to number 4 in Table 7.4, which describes the alcoholic fermentation
using yeasts from glucose (Lee et al., 1983). In particular, this model has been
employed for continuous processes, as reported by Tsuji et al. (1986). It was one of
the models employed for the subsequent stages of process synthesis procedures to
be discussed in this book. On the other hand, number 5 proposed by Garro et al.
(1995) was selected for fermentation using Z. mobilis