초록
<P><B>Abstract</B></P> <P>The <I>Synechocystis</I> sp. PCC 6803 is a promising host for ethanol biosynthesis from CO<SUB>2</SUB>. In this study, the production of ethanol was performed by utilizing two different engineered <I>Synechocystis</I> strains consisting of <I>pdc</I>-<I>adh</I> (pyruvate decarboxylase and alcohol dehydrogenase) overexpression (▲APX) and <I>glgC</I>-<I>phaA</I> (glucose-1-phosphate adenylyltransferase and PHA-specific β-ketothiolase) knockout (ΔGBK) pathways. This strategy involves destruction of glycogen and polyhydroxybutyrate (PHB) synthesis, both of which act as a storage polymer. The blocking of such biosynthetic pathways enabled <I>Synechocystis</I> to release various metabolites into the medium with an increase of chlorophyll <I>a</I> content and oxygen evolution due to the reduction of glycogen and PHB synthesis. In co-cultivation system, the extracellular metabolites released from knock out strain (ΔGBK) were utilized by the <I>pdc</I>-<I>adh</I> overexpressing strain (▲APX) and produced 4708 mg/L ethanol, which is comparatively higher than <I>pdc</I>-<I>adh</I> overexpressing strain containing <I>glgC</I> and <I>PhaA</I> knock out (ΔGBK-▲APX) (4103 mg/L). Although the concentration of ▲APX cells were lower in co-culture than in mono-culture, the overflow of metabolites from knock out <I>Synechocystis</I> and the consumption of those products by <I>pdc</I>-<I>adh</I> overexpressing <I>Synechocystis</I> in co-cultivation system improved the overall yield.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pyruvate decarboxylase from <I>Saccharomyces cerevisiae</I> was expressed in <I>Synechocystis.</I> </LI> <LI> Destruction of glycogen and PHB synthesis causes overflow of metabolic products. </LI> <LI> Co-cultivation of two different engineered <I>Synechocystis</I> improved the ethanol yield. </LI> <LI> Engineered strains were tolerant to NaCl and sorbitol stress conditions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Schematic representation of enhanced ethanol production under co-cultivation of engineered <I>Synechocystis</I> sp. PCC 6803 strains.</P> <P>[DISPLAY OMISSION]</P>