Figure 8.6a shows that at kd≤4·10^4 h−^1 (or tb≥1.2·10^4 h; see Box 8.1) in a batch system,
constant substrate and biocatalyst costs were found. This can only result from the fact
that the maximum attainable product concentration is reached (see Box 8.2). The latter
implicates that at kd ≤4·10−^4 h−^1 the substrate conversion x is maximal; note that at
kd<4·10−^4 h−^1 , maximal substrate conversion is obtained before the stop moment, at t=tb,
is reached. At kd≤4·10−^4 h−^1 , biocatalyst productivity Pr (in kg of product per kg
Figure 8.6 The substrate, biocatalyst,
investment and operating,
downstream-processing, and overall
costs per kg of product ($s, $c, $dp, $dp
and $ov, respectively) as a function of
the first-order rate constant for
biocatalyst inactivation (kd) in a batch
reaction crystalliser (a) and in a
continuous reaction crystalliser
without biocatalyst losses due to wash-
out and with a feed flow decreasing in
accordance with the biocatalyst
inactivation rate
Solid-to-solid bioconversions 255