Acetone and isopropanol are important chemicals for the industry. They are used to produce materials from jet fuel to solvents to cleaners to plastics. Currently, the industry produces these two chemicals from oil using processes that release carbon dioxide and other greenhouse gases. Researchers have now developed a new fermentation process that efficiently converts carbon monoxide gases into acetone and isopropanol. Researchers used a combination of genomic analyzes, computer models and optimization of metabolic pathways outside the cells to design bacterial strains. The result is bacteria that convert carbon waste into valuable materials.
Scientists developed a process to convert industrial, agricultural and urban exhaust gases into important chemicals. This process captures more carbon gas than it releases. Scientists call this “carbon-negative” bioproduction. The new approach enables industry to produce plastics, fuels and other chemicals in a more sustainable way. This approach will also lead to faster development of efficient cell-based production methods. This will reduce greenhouse gas emissions and other environmental impacts of industrial activity.
Researchers from Oak Ridge National Laboratory, LanzaTech Inc., Northwestern University and University of Tennessee used an interdisciplinary approach to optimize strains of the bacterium. Autoethanogenic Clostridium maximize the production of acetone and isopropanol from exhaust gases. Scientists first searched the genomes of a collection of industrial strains for higher enzymes that produce acetone and isopropanol. They tested multiple combinations of those enzymes in these bacteria to select the most efficient engineered sets of enzymes. The team then further optimized those metabolic pathways using computational modeling, cell-free enzyme screening, and proteomic analyzes to identify metabolic bottlenecks and competing pathways. Finally, they adapted the process for high speed and stability and increased the crops to 120 liters for continuous conversion of the exhaust gases to acetone or isopropanol.
Applying a life cycle analysis, the team demonstrated that this bioproduction approach reduced greenhouse gas emissions by 165% compared to fossil fuel-based processes. While the production of these two chemicals from fossil fuels releases carbon gas, this biological process captures the carbon. These results show that the engineered acetogenic bacteria enable the production of sustainable, highly efficient and highly selective chemicals. This multi-faceted optimization of the strain and process demonstrates the potential for continued advances in biotechnology to shift industrial practices towards more sustainable methods.
Funding was provided by the Biological and Environmental Research Program of the Department of Energy (DOE) of the Office of Science and the Office of Bioenergy Technologies of the Office for Energy Efficiency and Renewable Energy. DNA synthesis was provided by the DOE Joint Genome Institute’s Community Science Program. The authors also acknowledge the support of LanzaTech’s private investors.