TABLE OF CONTENTS The cell is the ultimate reactor. It is the essential and in some cases the only possible route to the production of complex compounds [1-1]. Bioreactors (fermenters) are the key unit operation in biopharmaceutical, brewing, biochemical, biofuel, and activated sludge processes. Each bioreactor relies on the performance of billions of these individual reactors or cells. Process control attempts to influence the sophisticated metabolic reactions inside the cell by controlling the environment immediately outside of the cell [1-2].
| Note | Process control attempts to influence the individual sophisticated internal reactions of billions of cells by controlling their extracellular environment. |
In order to control a process variable, we must measure it directly or infer it from other measurements. The key process variables of the cells' environment that are measured are compositions and conditions, such as temperature, pH, dissolved oxygen and carbon dioxide, and substrate. In process control, the compositions and conditions in the broth or vent gas are termed process outputs and the quantity, composition, and condition of feeds or charges into the bioreactor or of coolant into coils or jacket are termed process inputs. Seed cultures, nutrients, substrates, air, and oxygen are process inputs. In basic feedback control, process outputs that are measured or inferred are controlled by manipulating the process inputs. The goal of process control is to transfer variability from important process outputs to the process inputs designed to be manipulated. How well the process outputs are controlled is determined by loop dead time,...
