STTR Phase I: Using mining waste as a feedstock for the production of chemicals from CO2 with genetically engineered Acidithiobacillus ferrooxidans

The broader impact/commercial potential of this Small Business Technology Transfer (STTR) project is the development of technology for use of sulfide mining waste streams as a novel energy source for the production of chemicals from CO2. Sulfide mining wastes pose a serious, perpetual environmental risk, and are continuously generated as by-products of mining operations. The sulfide minerals in mining waste also are viable energy source for a diverse community of microbes that derive their energy from the oxidation of these minerals. This biological oxidation releases significant amounts of energy from the rock. The energy released from one ton of sulfide mining waste is approximately equivalent to one barrel of oil. Approximately 95% of copper ores are found in sulfide-rich ore deposits and at about 20 million metric tons annually, constitute ~15% of mining waste (representing millions of barrels of oil). From genetically engineered microbes, it is proposed to use this energy to generate chemicals from CO2. As such, sulfide waste streams represent a new high energy feedstock for the sustainable production of chemicals from CO2. This technology will improve the sustainability of mining and provide a non-agricultural, non-photosynthetic and economically attractive route to carbon-neutral chemicals. This STTR Phase I project proposes to demonstrate the development of genetically modified A. ferrooxidans for the utilization of mining process waste streams as a feedstock for biotechnology applications. Readily available sulfur-rich waste streams produced during the traditional smelting processing of copper contain about 40% per metric ton of the energy of glucose, and about 20 million metric tons are produced annually in the U.S. These energy intensive waste streams are currently landfilled, and their environmental oxidation can lead to acid mine drainage. To leverage this opportunity, the ability to rationally engineer this species to produce isobutyric acid from atmospheric CO2 has been developed. The specific aims of this proposal are: 1) develop model reactor systems to characterize performance and operations using actual mine tailing feedstocks; 2) improve biological productivity through further metabolic engineering of A. ferrooxidans; and 3) develop a sophisticated techno-economic analysis of the novel bioprocess. In addition, a commitment from a mining company for access to a tailing feedstock supply and a site to construct and operate a pilot-scale plant will be secured. Accomplishing these goals will prepare for a future follow-on Phase II proposal to scale-up our technology, further characterize performance on actual process streams, and demonstrate large-scale process feasibility.