New constructs for ethanol production via cyanobacteria

Alternatives to fossil fuels must be developed due to several already known reasons. Bioethanol can be an attractive energy concept. Bioethanol gasoline hybrid fuel can be used by most internal combustion engines. First and second generation bioethanol production is already available - here agricultural crops or residues are utilised. There are controversial discussions about these bioethanol production methods - the food versus fuel debate, cost and energy efficiency. Alternative advanced bioethanol production must be established with competitive production costs. Photosynthetic prokaryotes like cyanobacteria are attractive organisms for this purpose - these prokaryotes are fast growing organisms and utilize solar energy and CO2. But these prokaryotes must be genetically manipulated for ethanol production. In this study transformation was performed using homologous recombination to introduce the pyruvate decarboxylase (pdc) and alcohol dehydrogenase B (adhB) genes of Zymomonas mobilis into the photosynthetic prokaryote Synechococcus elongatus PCC 7942 genome. These cyanobacteria grow in fresh water and seawater or even in wastewater. Both genes were expressed under the control of the strong constitutive promoter of psbA1 gene (encoding photosystem II protein D1). Various cloning strategies were done. Each construct was transformed successful in Synechococcus elongatus PCC 7942 and the potential bioethanol production was determined with HPLC. Only one construct produces bioethanol at detectable level. Diverse reactors and scale up steps were done to increase the bioethanol production. Anyhow further cloning strategies must be implemented to improve the production rate to achieve an effective bioethanol production from Synechococcus elongatus PCC 7942.