Lactic acid bacteria have a relatively simple carbon and energy metabolism and pyruvate is the central intermediate in the metabolism of carbohydrates in L.lactis. The metabolic flux through pyruvate can be modulated by overproduction of specific enzymes (alpha-acetolactate synthase and pyruvate decarboxylase) and by deletion of the gene for lactate dehydrogenase (LDH).
This project entails two new strategies for metabolic flux control in l.Lactis. Activation of pyruvate dehydrogenase (PDH) will result in extra energy conservation = extra cell mass during acetate production. Inactivation of PDH under aerobic conditions will favour the production of flavour compounds diacetyl and acetaldehyde by L.lactis. The metabolism in L.lactis can be influenced by aeration. This is caused by decreased levels of NADH in the cells as a result of oxidation. If a specific enzyme is involved, we will engineer lactic acid bacteria with enhanced activity. This should lead to the lactic acid fermentations that can be switched effectively to complete other product formation by aeration.