In the search for solutions to cut atmospheric carbon dioxide, scientists at the University of Georgia's Bioenergy Systems Research Institute think they could have a winner. A genetically modified microorganism in their lab not only captures CO2, but processes it directly to make a valuable chemical. A further tweak may even get it to make fuel.
Pyrococcus furiosus normally likes it hot. This microbe lives in volcanic mud or around deep sea geothermal vents, and feeds like fury at 95ºC, fermenting carbohydrates and growing fast. But Michael Adams and his team in Georgia changed all that. Their genetic manipulations engineered a strain that will feed at somewhat lower temperatures: around 73ºC.
When exposed to hydrogen, this modified organism gives up its rapid growth habit. Instead, it devotes itself to taking up atmospheric CO2, which it wouldn't normally do, and reacting it with the hydrogen. The result is an acid, 3-HPA, with many industrial uses, notably as a feedstock for making acrylics. As Meredith Lloyd-Evans of Cambridge-based consultants Biobridge points out, “the starting materials for conventional production of 3-HPA can be toxic, so a biological route is very positive”.
With more genetic manipulations Adams and his colleagues believe they can get versions of P. furiosus to perform other chemical reactions, including the direct production of useable fuel. They'd be doing a similar job to the biocatalysts pioneered by California-based Carbon Sciences Inc. (see “Air Supply”, GF76) but with air-captured CO2 rather than power station emissions (see also ‘Better than trees?’, GF83).
Adams believes his route could prove both efficient and cost-effective. When plants or algae fix CO2 by photosynthesis, he points out, they store the energy as sugars, and further processing is needed to unlock this energy as ethanol fuel. He hopes to show a viable way to “remove plants as the middleman”.
And what of the wider consequences of unleashing such organisms from the confines of the lab? Lloyd-Evans is fairly sanguine. The (still relatively) high temperature needed for optimum growth makes it unlikely that either the modified strain would develop outside lab conditions, he says.