PHOTANOL - Photofermentative ethanol production through metabolic engineering of the cyanobacterium Synechocystis sp. PCC 6803 In order to meet future demands for liquid fuels in the face of declining fossil fuel reserves, biofuels such as ethanol are becoming increasingly important. Novel biofuel production methods are required to overcome some of the flaws of previous generations of biofuels, most notably the requirement for fertile soils and the destruction of biomass during processing. The photanol approach uses metabolic engineering to link photosynthesis of the cyanobacterium Synechocystis sp. PCC 6803 to fermentative pathways by introducing heterologous genes; hereby a variety of products can be biosynthesised using light as the energy source, carbon dioxide as substrate and water as the ultimate electron donor. In this study, the photanol approach was used to create an ethanol producing mutant Synechocystis strain by introducing pyruvate decarboxylase and alcohol dehydrogenase from Zymomonas mobilis. Physiological analysis revealed a detrimental effect of glucose, increased production rates at high light intensities and a yet to be resolved carbon leak through acetate. Observed ethanol production rates were highest, 0.51 mM g-1 h-1 or 4.08 mM OD730nm-1 day-1, in late exponential phase photoautotrophic cultures grown at a light intensity of 38 µE and reached a maximum concentration of ~8 mM. This indicated a rate of photofermentative ethanol formation competitive with other studies with relatively more efficient conversion of light energy to chemical energy in the form of a liquid biofuel compound.