frequency is considered as that which gives a higher productivity as well as an increased
stability in continuous production. These beneficial effects may be explained by the fact
that the control of pellet size increases the active surface of mycelia and increases
nutrient availability. Moreover, it prevents bed compacting and consequently, improves
overall mass transfer and substrate conversion.
Continuous production of Manganese Peroxidase (MnP)The production of a ligninolytic enzyme, MnP, is associated with nutrient nitrogen
limitation. This fact implies that MnP is typically produced during a very short period of
time, after which the enzyme is rapidly deactivated by extracellular protease secretion
and cell lysis due to the extreme nutritional conditions. In accordance with this, the extent
of the ligninolytic activity is rather limited and only achieved in batch cultures. The low
amount of enzyme obtained in such conditions makes its application for biotechnological
purposes rather impractical. Hence, it seems logical to develop an efficient production
system for these enzymes. Continuous operation appears to be a good choice, since it
would lead to the continuous production of the enzyme. However, this possibility needs
an additional requirement to displace batch fermentations; production has to be kept
stable,
Figure 11.11 Pellets of A. niger
corresponding to the bioreactor
operated with (left) and without (right)
pulsation.
Multiphase bioreactor design 346