UGA/NCSU team engineers hyperthermophilic bacterium to produce industrial chemical building blocks from CO2 and H2; ARPA-E project
Researchers at the University of Georgia and North Carolina State University have used a unique temperature-dependent approach in engineering a hyperthermophilic archaeon, Pyrococcus furiosus to be able to use CO2 and hydrogen to produce 3-hydroxypropionic acid, one of the top 12 industrial chemical building blocks.
The research, reported in the Proceedings of the National Academy of the Sciences (PNAS), was supported by the Department of Energy as part of the Electrofuels Program of the Advanced Research Projects Agency-Energy (ARPA-E) under Grant DE-AR0000081. (Earlier post.)
Microorganisms can be engineered to produce useful products, including chemicals and fuels from sugars derived from renewable feedstocks, such as plant biomass. An alternative method is to use low potential reducing power from non-biomass sources, such as hydrogen gas or electricity, to reduce carbon dioxide directly into products. This approach circumvents the overall low efficiency of photosynthesis and the production of sugar intermediates.
Although significant advances have been made in manipulating microorganisms to produce useful products from organic substrates, engineering them to use carbon dioxide and hydrogen gas has not been reported. Herein, we describe a unique temperature-dependent approach that confers on a microorganism (the archaeon Pyrococcus furiosus, which grows optimally on carbohydrates at 100°C) the capacity to use carbon dioxide, a reaction that it does not accomplish naturally.—Keller et al.
The team altered P. furiosus via the heterologous expression of five genes of the carbon fixation cycle of the archaeon Metallosphaera sedula, which grows autotrophically at 73°C. The research team then used hydrogen gas to create a chemical reaction in the microorganism that incorporates carbon dioxide into 3-hydroxypropionic acid.
The reaction can be accomplished by cell-free extracts and by whole cells of the recombinant P. furiosus strain. The recombinant strain carries out the reaction at some 30 °C below the optimal growth temperature of the organism in conditions that support only minimal growth but maintain sufficient metabolic activity to sustain the production of 3-hydroxypropionate.
The team suggests that their approach can be expanded to produce other important organic chemicals, all through biological activation of carbon dioxide.
Basically, what we have done is create a microorganism that does with carbon dioxide exactly what plants do—absorb it and generate something useful. What this discovery means is that we can remove plants as the middleman. We can take carbon dioxide directly from the atmosphere and turn it into useful products like fuels and chemicals without having to go through the inefficient process of growing plants and extracting sugars from biomass.
This is an important first step that has great promise as an efficient and cost-effective method of producing fuels. In the future we will refine the process and begin testing it on larger scales.—UGA Professor Michael Adams, corresponding author
Matthew W. Keller, Gerrit J. Schut, Gina L. Lipscomb, Angeli L. Menon, Ifeyinwa J. Iwuchukwu, Therese T. Leuko, Michael P. Thorgersen, William J. Nixon, Aaron S. Hawkins, Robert M. Kelly, and Michael W. W. Adams (2013) Exploiting microbial hyperthermophilicity to produce an industrial chemical, using hydrogen and carbon dioxide. PNAS doi: 10.1073/pnas.1222607110