초록
<P><B>Background</B></P><P>Cyanobacteria can be metabolically engineered to convert CO<SUB>2</SUB> to fuels and chemicals such as ethylene. A major challenge in such efforts is to optimize carbon fixation and partition towards target molecules.</P><P><B>Results</B></P><P>The <I>efe</I> gene encoding an ethylene-forming enzyme was introduced into a strain of the cyanobacterium <I>Synechocystis</I> PCC 6803 with increased phosphoenolpyruvate carboxylase (PEPc) levels. The resulting engineered strain (CD-P) showed significantly increased ethylene production (10.5 ± 3.1 µg mL<SUP>−1</SUP> OD<SUP>−1</SUP> day<SUP>−1</SUP>) compared to the control strain (6.4 ± 1.4 µg mL<SUP>−1</SUP> OD<SUP>−1</SUP> day<SUP>−1</SUP>). Interestingly, extra copies of the native <I>pepc</I> or the heterologous expression of PEPc from the cyanobacterium <I>Synechococcus</I> PCC 7002 (<I>Synechococcus</I>) in the CD-P, increased ethylene production (19.2 ± 1.3 and 18.3 ± 3.3 µg mL<SUP>−1</SUP> OD<SUP>−1</SUP> day<SUP>−1</SUP>, respectively) when the cells were treated with the acetyl-CoA carboxylase inhibitor, cycloxydim. A heterologous expression of phosphoenolpyruvate synthase (PPSA) from <I>Synechococcus</I> in the CD-P also increased ethylene production (16.77 ± 4.48 µg mL<SUP>−1</SUP> OD<SUP>−1</SUP> day<SUP>−1</SUP>) showing differences in the regulation of the native and the PPSA from <I>Synechococcus</I> in <I>Synechocystis</I>.</P><P><B>Conclusions</B></P><P>This work demonstrates that genetic rewiring of cyanobacterial central carbon metabolism can enhance carbon supply to the TCA cycle and thereby further increase ethylene production.</P>