The goal of electro-fuel research is to generate infrastructure-compatible transportation fuel through non-photosynthetic fixation of carbon dioxide. To achieve this goal, we are developing a cutting-edge two stage bioprocess. In the first stage, acetogenic microorganisms ferment carbon dioxide into acetate using hydrogen or carbon monoxide as reducing equivalents. The produced acetate is then used as feedstock in the second stage for producing bio-diesel using a metabolically engineered oleaginous microorganism.
Our research in the first stage focuses on improving the productivity of acetate production and maximizing the utilization of gaseous substrates, and includes the following efforts:
1) Optimizing the growth and physiology of acetogenic microorganisms to increase the productivity.
2) Design and evaluation of cell-recycle bioreactors for increasing the cell density and alleviating the inhibitory effects of fermentation products.
3) Design and construction of pressurized and hollow-fiber membrane bioreactors to increase the efficiency of gas utilization.
In the second stage, our study focuses on production of oil products using an engineered oleaginous microbe. Specifically, this microbe is utilized to grow on acetate which is a product of upstream fermentation, and make desired lipid/oil products such as different fatty acids. By changing the growth conditions, we are able to grow this microbe at a high cell density, as well as to convert acetate to oil products in a decent rate. We are also establishing a continuous bioreactor system to support high-titer oil production.