Solar-Powered Biofactory: Scientific Detail
The transformative focus of this research is to greatly enhance the efficiency with which solar energy can be used for fatty acid and lipid production for efficient, cost-effective conversion to liquid transportation fuels and other lipid-based products. This platform for renewable solar energy-to-biofuels conversion combines innovative metabolic engineering with state-of-the-art, large-scale bioprocess engineering.
All this is possible because the cyanobacterium being used (Synechocystis) is fast growing and robust in accommodating diverse environmental conditions. It can be cultivated over a wide range of salt and fixed-nitrogen concentrations and at CO2 levels of up to 5 percent. The system also requires minimal water consumption. These traits make the microorganism well suited for growth using cement plant emissions or flue gas effluent from power plants as a carbon source (recapturing the carbon dioxide from the plant before release into the atmosphere) and using agricultural run-off water contaminated with nitrogenous fertilizer as a fixed-nitrogen source when it is available. When N-contaminated water is not used, fixed nitrogen can be recycled so little new nitrogen will need to be added.
Synechocystis is readily modified genetically to produce and secrete fatty acids. By optimizing this process so that it occurs throughout the cell’s life cycle, including in stationary phase, two major advantages occur: (1) more of the harvested energy can be used for fatty acid and lipid production as less energy needs to be applied toward growth, and (2) fatty acid secretion minimizes downstream processing complexity and cost of production. In this approach, as continuous growth of the culture is not required, the main inputs are CO2 and light, and the main output is fatty acid. Thus, the transformative breakthrough in our approach is that the cyanobacteria are not a biomass product that must then processed; they are a biocatalyst and a cellular factory for the products (fatty acids) that can be directly harvested.
‘The 2,000-liter photobioreactor at ASU provides a means of culturing Synechocystis under natural conditions at pilot scale.’
This research program yields a path toward efficient solar energy conversion to fungible liquid transportation fuels and, at scale, will have a significant impact on environmentally responsible, domestic production of fuels. As a stepping stone into the high production realm of liquid transportation fuels, the secreted fatty acids could be utilized in green personal care products. This advances the systems development and optimization leading to a responsible and economically feasible scale-up of the technology.
Arizona State University is teamed with North Carolina State University and Diversified Energy Corporation to deliver this revolutionary technology towards environmentally responsible fuel production using a unique process (called Centia™) that converts fatty acids to fuel. Cyanobacteria produce fatty acids that serve as the feedstock for the Centia™ process that converts fatty acids to alkanes and other liquid fuel components. Therefore, this program provides a transformative end-to-end solution delivering a fully fungible drop-in fuel replacement within existing distribution infrastructure.