Multivariable multi-strategy control of a fed-batch fermentation process for the production of poly-β-hydroxybutyric acid (PHB)

A fermentation process has been developed for the production of a biodegradable plastic, poly-β-hydroxybutyric acid (PHB). The process involves progressive and independent addition of four groups of nutrients in a multi-fed-batch mode. Control strategies used for the addition of these nutrients varied according to the different process stages. The control laws developed to implement the control strategies are based on an adaptive nonlinear control approach. Careful selection of the control strategies and the application of modern control techniques resulted in a process with high cell density, high PHB content in cells, and PHB of good quality