초록
<P><B>Abstract</B></P> <P> <I>Synechocystis</I> sp. PCC 6803 strains overexpressing <I>pha</I> genes were constructed and characterized for poly-3-hydroxybutyrate (PHB) production. These <I>pha</I> overexpressing strains showed slightly reduced growth rates. Under N-deprived condition, the strains overexpressing (OE) <I>phaAB</I>, <I>phaEC</I> and <I>phaABEC</I> showed significantly higher PHB contents than the wild type. The maximum PHB content, a 2.6-fold increase producing 26% PHB (dcw), was observed in OE <I>phaAB</I> cells grown for 9days in N-deprived medium. Under this condition, these OE <I>phaAB</I> cells increased PHB production to 35% PHB (dcw) upon addition of 0.4% (w/v) acetate. Higher PHB granules in OE <I>phaAB</I> cells were clearly visualized by both Nile red staining and TEM imaging. All OE strains under N-deficient condition had increased <I>glgX</I> transcript levels. Overall results demonstrate an enhanced PHB production in <I>Synechocystis</I> cells overexpressing <I>pha</I> genes, particularly <I>phaA</I> and <I>phaB</I>, when grown in N-deprived medium containing 0.4% (w/v) acetate.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Native biosynthetic genes for PHB production overexpressed in <I>Synechocystis.</I> </LI> <LI> Overexpression of <I>phaA</I> and <I>phaB</I> resulted in the highest level of PHB. </LI> <LI> Metabolic engineering leads to increased production of the valuable polymer PHB. </LI> </UL> </P>