Bacterial Biofuel Production Gets a Boost

Researchers at Oak Ridge, Tennessee, have engineered a bacterium that converts waste plant matter into the biofuel, isobutanol, 10-times more efficiently than before. Scientists at the Department of Energy’s BioEnergy Science Center (BESC) at Oak Ridge, in collaboration with the University of California at Los Angeles, took a synthetic biology approach to engineering Clostridium thermocellum to produce the industrially-important isobutanol. This brings industrial production of isobutanol using waste plant matter (cellulose) instead of food crops, such as corn, closer to realisation.

Isobutanol is an attractive biofuel for many reasons. It can be readily used in existing petrol-powered engines, or mixed with the gasoline at any ratio. As a solvent, isobutanol is often mixed with paint, varnish remover and ink. It is also a precursor in many plastics, and is regarded as the “safest” of the butanol chemicals produced by Clostridium bacteria.

In Clostridium thermocellum, the researchers have constructed a microbe adapted for extracting sugar from cellulose and converting those sugars into isobutanol. Plant matter tends to naturally defend itself against breaking down, known as recalcitrance. Recalcitrance is a major barrier to using the leftovers after farming crops, such as corn stover, as feedstock for bacterial fermenters. This new bacterial strain produces 5-6 grams of isobutanol per litre of feedstock. While this is a 10-fold increase on previous attempts in Clostridium cellulolyticum, it’s still short of the 20 grams per litre needed for commercial adoption of the method.

Director of BESC, Paul Gilna, was optimistic of the other advantages afforded by using Clostridium thermocellum, “… the prospects of commercial realization of this approach are greatly enabled by the fact that the microbe works at temperatures high enough to keep competing bugs from contaminating the microbial fermentation tanks and interfering with the conversion process.”

The paper is available at

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Dr David Kirk
Dr David Kirk is a science communicator and researcher with biotech start-up CHAIN Biotechnology Ltd in Nottingham, UK. He works on the microbial engineering of Clostridia for high-value chiral chemical synthesis. He completed his PhD in 2015 on bacterial spore formation at the University of Helsinki, Finland. He plays badminton (poorly) and maintains a blog on science news and synthetic biology: His views are his own. Twitter: @DrDaveKirk Blog: Research:

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