Scientists working to make exact chemical copies of fossil fuels from living microbes say they have scored a major victory in the lab. Merging genes from the camphor tree, soil- and gut-dwelling bacteria, and a microorganism that is lethal to insects, researchers have produced molecular replicas of petroleum-based fuels.
The team, composed of researchers from Exeter University in the United Kingdom and Shell, engineered the DNA of E. coli, a bacterium commonly found in the gut of mammals, to alter how it metabolizes its food so that it excretes the fossil-fuel replicas.
The new fuel doesn’t need to be heavily processed after it’s produced to work in combustion engines, says study coauthor John Love. It could be a solution that bypasses a major hurdle for conventional biofuels, which are not fully compatible with vehicles already out on the road.
“Modern engines are not suited to using these biofuels without major modifications and/or loss of performance,” Love, an associate professor of plant and industrial biotechnology at the University of Exeter, tells Txchnologist. “Ideally, you’d want to replace the fossil fuel with a biofuel that matches it exactly in chemical structure. We have engineered bacteria to produce such a fuel: biological gasoline or bio-alkanes. These hydrocarbons can be added directly to any engine, including a jet engine.”
No more blends?
Current retail biofuels are either alcohols or biodiesels that are structurally different from petroleum-derived energy sources, so they must be blended with fossil fuels to keep machines operating correctly. These biofuels can only comprise a maximum of 20 percent of the total fuel fed into engines without redesigning the machinery. “Without a dramatic change in vehicle technology and fuel supply infrastructure, 80–90 percent of transport fuel demand cannot be met through replacing petroleum-derived fuels with the biofuels currently available,” the team wrote in a paper published this month in the Proceedings of the National Academy of Sciences.
The genes they have engineered into E. coli allow the microbe to convert free fatty acids into hydrocarbons. One set of instructions came from Photorhabdus luminescens, the bacterial insect pathogen that normally lives in the gut of a nematode. Another set came Nostoc punctiforme, a cyanobacteria that grows on rocks, in lakes and in the soil.
Love says they also stitched in a gene from the camphor tree, which produces the essential oil long used for medicine, incense and food. This important component of the synthetic genome lets E. coli “tailor the length of the fatty acid chain to that which is required for use in retail fuel,” he says. “We therefore do not have to ‘crack’ a longer hydrocarbon to the required length, thereby saving energy and avoiding chemical pollution.”
Synthetic biology redesigns bacteria
In the paper, the researchers say they haven’t rebuilt the metabolic routes the E. coli would have used to make alcohols. Instead, they completely redesigned the molecular pathway to produce retail-ready fuel. Their innovation could also create a new use for waste that society has long struggled with: While the engineered bacteria are currently being fed glucose to make the biofuel, Love says there’s no reason they couldn’t feast on waste plant biomass, animal waste or even human sewage.
Now that they have proven their concept in the lab, they are working to understand the volume of biological gasoline their designed microbe can produce. Since Shell is interested in their work for commercialization potential, they have given the research team yield targets that their germs must meet. If they meet those targets, Love says, their biofuel experiment will be producing more energy than it uses, a major step needed to make it a logical alternative to fossils.
“We specifically produce retail grade hydrocarbons in one bacterium,” says Love. “For the consumer, this means that you may be able to use your car, without modifications, running on biofuel.”
Top Image: Escherichia coli bacteria via Shutterstock.