Implementation of a Disassociated Fatty Acid Synthase System (FAS type II) in Saccharomyces Cerevisiae for Fatty Acid and Wax Ester Production

Microbial biosynthesis of fats and oils from renewable carbon sources has attracted significant attention in recent years for the potential production of biofuel and other commodities. Almost all organisms synthesize de-novo fatty acids via a well conserved cyclic series of four reactions involving the condensation, reduction, dehydration and reduction of carbon-carbon bonds. In nature there are two main types of fatty acid synthase systems (FAS), type I and type II. FAS I systems utilize a single large, multifunctional polypeptide and are common to both mammals and fungi, although with some structural differences. On the other hand, Plants and Bacteria’s (as well in mitochondria and chloroplasts) utilize the disassociated FAS type II system. The reactions of the type II FAS, unlike FAS I, are catalyzed by discrete and monofunctional enzymes, the proteins are all expressed as individual polypeptides from separated genes. The organization of FAS II enables the synthesis of several fatty acid products and is more amenable to modification of chain length. The separation of functions in single polypeptides also facilitates the metabolic optimization of each reaction step along the sequence, which is impossible with FAS I, since the subunits are stoichiometrically fixed. In this work we implemented a FAS II system consisting of 12 individually expressed genes in a S. cerevisiae strain carrying a conditional allele of the fatty acid synthase genes of the endogenous FAS system. The physiological consequences of this expression will be discussed.

This work was funded by the FCT project MycoFat PTDC/AAC-AMB/120940/2010. F.A. was supported by an FCT fellowship SFRH/BD/80934/2011. This work was supported by FEDER through POFC – COMPETE and by Portuguese funds from FCT through the project PEst-OE/BIA/UI4050/2014