Biosynthesis of biodegradable polyhydroxyalkanotes biopolymers in genetically modified yeasts

In the recent decade, biosynthesis of the degradable biopolymers polyhydroxyalkanotes in transgenic yeasts became an important research task. Most research strategies depend on either metabolic engineering or molecular approaches. In the present work, research compared PHA biosynthesis in two types of yeasts; Saccharomyces cerevisiae and a non-convenient Kloeckera spp. Yeast strains were equipped in their cytoplasm with the phaABC(Re) operon containing genes phbA, phbB and phbC of the PHA biosynthetic pathway of Ralstonia eutropha, which encode beta-ketothiolase, NADPH-linked acetoacetyl-CoA reductase and PHA synthase, respectively. The transgenic strains Saccharomyces cerevisiae and Kloeckera sp. were able to produce PHA. The maximum content of the polymer detected in the recombinant strain INVSc1/PHA1 was 2.68 % and only poly-3-hydroxybutyrate (PHB) accumulated. However, the non-conventional transgenic strain KY1/PHA was able to accumulate as maximum of 7.06% of the copolymer poly-(3-hydroxybutyrate-co-poly-3-hydroxyvalerate) (PHV). Western blot analysis confirmed expression of the phaABC(Re) operon in the transgenic yeast strains. The nature of the PHA thus produced by all tested strains was analyzed by H-1 and C-13 nuclear magnetic resonance (NMR) spectroscopy.