Computer control of the penicillin fermentation using the filtration probe in conjunction with a structured process model

A structured model for the penicillin fermentation is presented. This model includes three different cell types: (1) hyphae tips, (2) penicillin-producing cells, and (3) degenerated, metabolically inactive cells. Cell degeneration has been described previously as a gradual loss of cytoplasmic material by endogenous metabolism. The rate at which such loss of cytoplasm (and activity) proceeds can be expressed as a linear function of the specific growth rate. At growth rates above some minimum value (0.0115 h(-1)) cell degeneration can be prevented. This model served as the control basis during open-loop as well as closed-loop computer control of the fermentation. Closed-loop control was achieved through feedback information of biomass concentration using a filtration probe and was required when complex nutrients contributed significantly to the overall biomass production.