Making rocket fuel from plants is not rocket science. It is, however, a notoriously inefficient, multistep process, which has made it difficult to scale up to the level needed to compete with fossil fuels. But researchers at the U.S. Department of Energy’s Berkeley Lab think they’ve figured out how to cook it up in one go using genetically engineered bacteria.
In an article published today in the journal Green Chemistry, they offer up their “one-pot” recipe that they think “is a critical step in making biofuels a viable competitor to fossil fuels because it helps streamline the production process.” Here are those ingredients:
Mutant E. coli
Simple, right? With their newly discovered strain of bacteria, they write, you can throw the ingredients into a metaphorical crockpot and let them stew, unsupervised. It’s a huge achievement in the biofuel industry because it bypasses all of the expensive, labor-intensive steps that hampered production in the past.
Here’s how it works: What we really want from plants is their carbon-containing sugars, but their tough structural components and sinewy compounds like cellulose and lignin are hard to break down. To get to the carbon in these molecules, scientists treat plant material with liquid salts, which help the plants release their sugars in a step called saccharification. Then, they add bacteria to the mix, which converts sugar into biofuel (ethanol, mostly) in a process similar to turning grape juice into wine.
There’s just one problem: Most bacteria can’t deal with the liquid salts, so each step of the procedure has to be done separately. It’s an inefficient process, but the liquid salts are too effective to eliminate. Compared to the enzymes that used to do their job, the salts are incredibly potent.
The only other way to streamline the process was to find tougher, more salt-tolerant bacteria. And that’s exactly what the researchers did.
Building on previous studies, they genetically engineered a strain of E. coli containing a gene mutation that makes it highly tolerant to the salts. Testing this E. coli in a jet-fuel recipe involving pretreated sweetgrass, they found their new bacteria survived the salt treatment and succeeded in producing biofuel in a single step.
They’re hoping the discovery will make it possible to convert any renewable carbon source into fuel.
“Being able to put everything together at one point, walk away, come back, and then get your fuel, is a necessary step in moving forward with a biofuel economy,” says the study’s principal investigator, Aindrila Mukhopadhyay, Ph.D. “This study puts us one step closer to this moonshot.”