The results presented here clearly indicate the positive effect of
increased CO2 concentrations by the reduction of aeration rates
and increased pressure on the production of a-amylase and protease
during the fermentation process with B. caldolyticus. The
reduction of aeration rate of 0.1 vvm in combination with the
increasing overhead pressure to 2 bar resulted in an increased
production of a-amylase and protease by 123% and 52%, respectively
compared to standard fermentation conditions of 1 vvm
and atmospheric overhead pressure. Furthermore, the fermentation
strategy with the increased pressure in combination with
reduced aeration rates enables the simulation of large scale bioreactors
which have high hydrostatic pressure and comparable low
aeration rates. This strategy for process development in small scale
bioreactors might help to overcome problems during scale-up of
fermentation processes. Incremental cost of operating the bioreactors
at these new conditions appears to be quite small.