DIRECTFUEL

Direct biological conversion of solar energy to volatile hydrocarbon fuels by engineered cyanobacteria

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 Obiettivo del progetto (Objective)

'The objective of the DirectFuel project is to develop photosynthetic microorganisms that catalyze direct conversion of solar energy and carbon dioxide to engine-ready fuels. A key process target of the proposal is 'direct' in the sense that fuel production should not require destructive extraction and further chemical conversion to generate directly useable transport fuels. To further increase our chances of delivering a functioning process we target only non-toxic end-products that have been demonstrated to function in existing or minimally modified combustion engines. From the above criteria, we have chosen to develop an exclusively biological production process for the volatile end-products ethylene and short-chain n-alkanes ethane and propane in photosynthetic cyanobacteria. As no natural biochemical pathways are known to exist for short-chain alkane biosynthesis, we first identify potential gene candidates through informatics analysis and then tailor the substrate specificities of the encoded enzymes by enzyme engineering. In order to directly capture solar energy to drive fuel biosynthesis, the synthetic pathways are at first assembled in the photosynthetic model organism Synechocystis sp. PCC 6803. It is highly unlikely that mere 'introduction' of novel biochemical pathways will result in high-yield synthesis of desired end-products. The final key step is therefore to optimize native host metabolism to deliver reducing energy and metabolic precursors to the synthetic pathways with maximum metabolic flux. Successful construction of the intended strains would allow low-cost production of transport fuel in a potentially neutral 'greenhouse gas' emitting process that does not compete for agricultural land. The proposed project is highly relevant to the call as we construct 'new metabolic pathways' that catalyze 'direct' production of 'gaseous fuels for transport' 'directly from solar radiation'.'

Introduzione (Teaser)

Photosynthetic organisms produce energy from carbon dioxide and water in the presence of sunlight. Tapping into that potential, scientists are engineering photosynthetic bacteria to produce hydrocarbon fuels for human transport.

Descrizione progetto (Article)

Engineering aquatic photosynthetic organisms to produce large quantities of engine-ready fuels for human transport presents an exciting opportunity. It would enable low-cost, low-emission production of engine fuel in a process that does not compete for agricultural land.

EU-funded scientists are working toward realisation of this potential within the project (http://www.directfuel.fi (DIRECTFUEL)). They are developing the production process for the volatile fuels ethylene and short-chain alkanes (e.g. ethane and propane) in cyanobacteria. A combination of enzyme and metabolic engineering are paving the way.

During the second project period, scientists studied two enzymes catalysing the native alkane biosynthetic pathway in cyanobacteria. Researchers successfully modified the gene encoding the enzyme that catalyses the final step in the biosynthetic pathway for greater utilisation of available substrates. Enzyme activity was evaluated via a novel in vivo method that provided unprecedented insight into the regulation of the alkane pathway in cyanobacteria.

Investigators updated a model to predict the potential energy yield of various biofuel pathways based on metabolic changes related to changes in light. In addition, numerous cyanobacteria strains were created to produce fuels or precursors to fuels. Researchers established a novel protocol for the first time to enable genome-scale screening for conditionally essential genes. It should help optimise the model predicting energy yield and provide novel insight into gene functionality.

DIRECTFUEL is well on its way to demonstration of the technical and economic feasibility of industrial-scale production of carbon-based fuels and chemicals by cyanobacteria. Further, a life cycle analysis of a full-scale fuel production facility fully supported the environmental benefits of replacing petrochemical refining with photobiological production. Scientists are breaking new ground in preparation for a transitional solution to reduce dependence on diminishing fossil fuel reserves.