초록
<P>Ethylene is widely used in the petrochemical industry and has traditionally been produced <I>via</I> the steam cracking of petroleum-based feedstock. The exploration of sustainable and carbon-neutral methods of producing ethylene from the renewable feedstock seems promising. The direct photosynthetic production of ethylene after the recycling of carbon dioxide shows great potential. In this study, continuous and stable ethylene production was achieved in <I>Synechocystis</I> sp. PCC 6803 by introducing a codon-optimized ethylene-forming enzyme (EFE) from <I>Pseudomonas syringae</I> pv. <I>sesami</I> and using 2-oxoglutarate (2-OG) as the substrate. Based on diverse promoter screening, P<I>cpcB</I> was proved to be a highly efficient promoter for ethylene production in cyanobacteria. The genes encoding 2-OG decarboxylase (OGDC) and succinic semialdehyde dehydrogenase (SSADH) in the tricarboxylic acid (TCA) cycle in <I>Synechocystis</I> sp. PCC 6803 were identified, and the TCA cycle was genetically modified by blocking these two enzymes with the simultaneous overexpression of EFE. Meanwhile, a gene encoding 2-OG permease (KgtP) from <I>E. coli</I> was introduced into the <I>phaAB</I> loci to increase the 2-OG supply. A peak volumetric production rate of 9.7 mL L<SUP>−1</SUP> h<SUP>−1</SUP> for ethylene was eventually achieved in the <I>Synechocystis</I> recombinant (XX110), with the genetic modification of the TCA cycle and heterologous expression of 2-oxoglutarate permease by the modified semi-continuous cultivation.</P><BR><BR><P>Graphic Abstract</P><P>The enhanced ethylene production (9.7 mL L<SUP>−1</SUP> h<SUP>−1</SUP>) was achieved by genetic modifications and improved cultivation of <I>Synechocystis</I> sp. PCC 6803.<BR><IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4gc01730g'><BR></P>