Ethanol synthesis by genetic engineering in cyanobacteria

Cyanobacteria are autotrophic prokaryotes which carry out oxygenic photosyn thesis and accumulate glycogen as the major form of stored carbon. In this research, we introduced new genes into a cyanobacterium in order to create a novel pathway for fixed carbon utilization which results in the synthesis of ethanol. The coding sequences of pyruvate decarboxylase (pdc) and alcoh ol dehydrogenase II (adh) from the bacterium Zymomonas mobilis were cloned into the shuttle vector pCB4 and then used to transform the cyanobacterium Synechococcus sp. strain PCC 7942. Under control of the promoter from the r bcLS operon encoding the cyanobacterial ribulose-1,5-bisphosphate carboxyla se/oxygenase, the pdc and adh genes were expressed at high levels, as demon strated by Western blotting and enzyme activity analyses. The transformed c yanobacterium synthesized ethanol, which diffused from the cells into the c ulture medium. As cyanobacteria have simple growth requirements and use lig ht, CO2, and inorganic elements efficiently, production of ethanol by cyano bacteria is a potential system for bioconversion of solar energy and CO2 in to a valuable resource.