Metabolic Engineering of the Model Photoautotrophic Cyanobacterium Synechocystis for Ethanol Production: Optimization Strategies and Challenges

Photoautotrophic ethanol production using model cyanobacteria is an attractive technol - ogy that offers potential for sustainable ethanol production as a biofuel. Model strains of Synechocystis PCC6803 have been metabolically engineered to convert central meta bolic intermediates such as pyruvate to acetaldehyde via cloned heterologous pyruvate decarboxylase and from acetaldehyde to ethanol via cloned homologous or heterologous alcohol dehydrogenase. While the technology is now proven, strategies are required to increase the ethanol levels through metabolic and genetic engineering and in addition, production and process strategies are required to make the process sustainable. Here we discuss both genetic and molecular strategies in combination with do wnstream strate gies that are being applied while also discussing challenges to future application.