Synthesis of polyhydroxyalkanoate in the peroxisome of Saccharomyces cerevisiae by using intermediates of fatty acid beta-oxidation

Medium-chain-length polyhydroxyalkanoates (PHAs) are polyesters having prop erties of biodegradable thermoplastics and elastomers that are naturally pr oduced by a variety of pseudomonads. Saccharomyces cerevisiae was transform ed with the Pseudomonas aeruginosa PHAC1 synthase modified for peroxisome t argeting by the addition of the carboxyl 34 amino acids from the Brassica n apus isocitrate lyase. The PHAC1 gene was put tinder the control of the pro moter of the catalase A gene. PHA synthase expression and PHA, accumulation were found in recombinant S. cerevisiae growing in media containing fatty acids. PRA containing even-chain monomers from 6 to 14 carbons was found in recombinant yeast grown on oleic acid, while odd-chain monomers from 5 to 15 carbons were found in PRA from yeast grown on heptadecenoic acid. The ma ximum amount of PHA accumulated was 0.45% of the dry weight. Transmission e lectron microscopy of recombinant yeast grown on oleic acid revealed the pr esence of numerous PRA inclusions found within membrane-bound organelles. T ogether, these data show that S. cerevisiae expressing a peroxisomal PHA sy nthase produces PRA in the peroxisome using the 3-hydroxyacyl coenzyme A in termediates of the beta -oxidation. of fatty acids present in the media. S. cerevisiae can thus be used as a powerful model system to learn how fatty acid metabolism can be modified in order to synthesize high amounts of PHA in eukaryotes, including plants.