Recent research on malic acid production in Saccharomyces cerevisisae involved metabolic engineering of this organism. In order to enable malic acid production, the reductive tricarboxylic acid (TCA) cycle branch (pyc and mdh) was targeted to the cytosol, and a heterologous malic acid transporter from Schizosaccharomyces pombe was expressed (Zelle et al. 2008).