Scientists, including one of Indian-origin, have engineered a strain of bacteria that enables a "one-pot" method for producing advanced biofuels from a slurry of pre-treated plant material.
The Escherichia coli (E coli) is able to tolerate the liquid salt used to break apart plant biomass into sugary polymers, researchers said.
Since the salt solvent, known as ionic liquids, interferes with later stages in biofuels production, it needs to be removed before proceeding, a process that takes time and money. Developing ionic-liquid-tolerant bacteria eliminates the need to wash away the residual ionic liquid.
The achievement is a critical step in making biofuels a viable competitor to fossil fuels because it helps streamline the production process, researchers said.
"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," said Aindrila Mukhopadhyay from the US Department of Energy's Lawrence Berkeley National Laboratory.
"The E coli we have developed gets us closer to that goal. It is like a chassis that we build other things onto, like the chassis of a car," said said Mukhopadhyay.
"It can be used to integrate multiple recent technologies to convert a renewable carbon source like switchgrass to an advanced jet fuel," she said.
The basic steps of biofuel production start with deconstructing the cellulose, hemicellulose and lignin that are bound together in the complex plant structure.
Enzymes are then added to release the sugars from that gooey mixture of cellulose and hemicellulose, a step called saccharification.
Bacteria can then take that sugar and churn out the desired biofuel. The multiple steps are all done in separate pots.
Researchers pioneered the use of ionic liquids, salts that are liquid at room temperature, to tackle the deconstruction of plant material because of the efficiency with which the solvent works.
However, what makes ionic liquids great for deconstruction also makes it harmful for the downstream enzymes and bacteria used in biofuel production.
They established that an amino acid mutation in the gene rcdA, which helps regulate various genes, leads to an E coli strain that is highly tolerant to ionic liquids.
They used this strain as the foundation to build on earlier work - including the ionic-liquid-tolerant enzymes - and take the steps further to the one-pot biofuel finishing line.
The findings were published in the journal Green Chemistry.
