ABSTRACT
In many fermentation processes the product yield YSP is a parameter of major economic importance. e theoretical maximum to the product yield for a certain organism and product, Yspmax , is determined by the stoichiometry of the product pathway and connected central metabolic pathways. e theoretical maximum product yield can be changed by changing the stoichiometry of the metabolic network by means of genetic interventions, such as:
Replacement of a transporter which consumes ATP by a transporter which does not (active trans-• port becomes passive transport or vice versa) Replacement of a decarboxylation reaction• Replacement of an NADPH consuming reaction by an NADH consuming reaction (or vice versa)• Introduction of a catabolic pathway for a novel substrate• Replacement of an ATP consuming reaction by a non-ATP consuming reaction• Introduction of an alternative product pathway•
e quantitative eects of such changes on the maximum theoretical yields of product, but also of biomass on substrate can be calculated with so-called stoichiometric metabolic models.
