Hydrocarbon production in genetically engineered cyanobacteria

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Cyanobacteria, photosynthetic bacteria with conversion capability to utilize solar energy as energy source and carbon dioxide as carbon source and with genetic engineering capacity to be easily modified to build non-native and improved native biosynthetic pathways, have displayed huge potential for biotechnology applications and for the production of biofuels. Hydrocarbons are the predominant constituents of gasoline, diesel, and jet fuels. The identification of a native hydrocarbon-producing pathway in cyanobacteria reported by Schirmer et al. in Science (2010) enlarged the potential for photosynthetic production of hydrocarbons by metabolic engineering in cyanobacteria further. However, there also exist some bottlenecks needed to be addressed, such as the low activities of fatty acyl-ACP reductase and fatty aldehyde decarbonylase or the lack of suitable promoters for the efficient expression of hydrocarbon-producing pathway genes in cyanobacteria. Moreover, the biological function of this native hydrocarbon-producing pathway, which has not been detected outside the cyanobacterial phylum and the regulatoryion mechanisms controlling its expression, are entirely unknown, but of potential relevance for the large-scale production of the resulting compounds.In order to significantly improve the production efficiency of hydrocarbons in cyanobacteria, we propose the following three research tasks:(1) To screen for improved enzymes involved in hydrocarbon-producing pathway with higher catalytic efficiency by directed evolution.(2) To screen the suitable promoters from the genome DNA pools of cyanobacteria for over-expression of hydrocarbon-producing pathway genes.(3) To analyze the expression pattern of cyanobacterial hydrocarbon-producing pathway genes under different culture conditions, and to identify the regulators responsible for gene expression.