Cytosolic Acetyl-CoA Platform in Yeast for Biochemicals Production

Acetyl-CoA is not only a key precursor for cell metabolism, but also is the important intermediate for production of biofuels and biochemicals. Saccharomyces cerevisiae is a very important cell factory and has been widely used for many biomolecules production, especially for bioethanol production.  However, the synthesis of cytosolic acetyl-CoA is not efficient enough for industrial application due to the organelle compartmentalization and hallmarks of yeast metabolism. In yeast, part of pyruvate was converted to acetyl-CoA in mitochondria by pyruvate dehydrogenase and pyruvate decarboxylase catalyzed major pyruvate to acetaldehyde for ethanol and acetyl-CoA production in cytoplasm. In order to eliminate ethanol accumulation, endogenous pyruvate decarboxylases (Pdc1p, Pdc5p, Pdc6p) were firstly deleted creating mutant strain S. cerevisiase E1. However, strain E1 could not grow in glucose medium due to no cytosolic acetyl-CoA produced for cell metabolism. Base on this platform, a heterogenous combination module was secondly introduced into this strain. In this module, pyruvate oxidase and phosphate acetyltranferase were coexpressed in cytoplasm to convert pyruvate to acetyl-CoA. Growth of E1 strain in glucose medium was rescued by the modifications, which indicate that this pathway could convert pyruvate to cytosolic acetyl-CoA for cell growth. In addition, there was no ethanol be detected in culture medium. With this cytosolic acetyl-CoA producing platform, a new non-ethanol producing yeast cell factory could be constructed to produce many industrially relevant chemicals.