Method for controlling fermentation growth and metabolism

Abstract

This invention is a method for controlling growth rate and metabolic state in fed-batch fermentations. Growth rate refers to the rate of exponential growth. Metabolic state refers to the relative consumption rates of the carbon and nitrogen sources. The method is based on a new use of the pH control reagent addition rate (RAR) and thus requires pH control and measurement of the RAR. The method also requires measurement of the oxygen uptake rate (OUR), or measurement of the biomass concentration (X) along with the reactor volume (V), or all three. Either the preferred embodiment or the first additional embodiment can be used when one metabolite limits growth and the metabolic state is determined by the organism through the growth rate. In the preferred embodiment, the controller feeds the growth-limiting metabolite such that the reagent-oxygen metabolic quotient, defined as RAR/OUR, is maintained at a set point corresponding to the desired growth rate. In the first additional embodiment, the controller feeds the growth-limiting metabolite such that the specific RAR, defined as RAR/XV, is maintained at a set point corresponding to the desired growth rate. A second additional embodiment can be used when two metabolites limit (growth and affect the metabolism. In this case, the multivariable controller feeds the two metabolites separately such that the specific RAR and the specific OUR, defined as OUR/XV, are maintained at a pair of set points corresponding to the desired growth rate and metabolic state.

Dependencies are inferred from the claim text.