ABSTRACT
In the early 1970s, fermentation processes were perceived to be as much art as science. The best indicator for a fermentation progress was the experience operator looking through a site glass and observing the color and texture of the foam layer on top and sometimes by smelling near to the bioreactor. The principal fermentation control requirement is population growth of the microorganism of interest. In its natural habitat, the microbe will respond to environmental stimuli such as excess nutrients by synthesizing enzymes and biomass capable of exploiting the resource as effectively as possible. A fermentation development program seeks to establish what control set points are needed for the control loops in the control system. In the 1940s, the sensors were largely based on manual sampling and offline analysis; control was improved through the 1950s and 1960s by the use of limited electrical signals controlling pneumatic outputs.
