Metabolic engineering of Saccharomyces cerevisiae for C4-dicarboxylic acid production

Biotechnological production of chemicals from renewable feedstocks offers a sustainable alternative to petrochemistry. Understanding of the biology of microorganisms and plants is increasing at an unprecedented rate and tools with which these organisms can be engineered for industrial application are becoming ever more powerful. However, biotechnological production processes that are cost-competitive with petrochemistry still have to be developed for many types of chemicals. In this thesis, the ability of Saccharomyces cerevisiae (baker’s yeast) to produce C4-dicarboxylic acids (fumarate, malate and succinate) is investigated. These acids, currently produced from oil in relatively small quantities and mainly applied for human consumption, have interesting properties for roles as commodity platform chemicals. First, S. cerevisiae was metabolically engineered for malate production via a pyruvate carboxylase-dependent pathway. While titers of nearly 60 g per liter were achieved, the fermentation process required oxygen, a significant drawback. Therefore, the second part of the research focused on improving process energetics by using phospho-enol-pyruvate carboxykinase or malic enzyme as alternative carboxylating enzymes. Interestingly, it was found that either enzyme could replace the anaplerotic function of pyruvate carboxylase, which offers the perspective of anaerobic and more efficient production of C4-acids with S. cerevisiae