E. coli turns seaweed into ethanol

A group of scientists from Berkeley has used an engineered form of the E. coli bacterium to turn sugars in seaweed into ethanol.

The breakthrough is attractive because if it could be commercialised, it would allow biofuels to be created without displacing crops or forests.

According to the report published in Science, the engineered bacteria can metabolize alginate, which is seaweed’s primary sugar constituent. Not only that, but it works without requiring heat or chemicals to pre-treat the seaweed, reducing the number of processing steps needed to create a biofuel.

DNA from E. coli – a workhorse in the lower intestine, but with a few strains that cause illness, giving it a poor reputation in the popular mind – was mixed with DNA from various marine microorganisms. These included Pseudoalteromonas, which provided genes to produce an enzyme to break up alginate; and Vibrio splendidus to digest the alginate.

The scientists claim the engineered E. coli yields “80 percent of the theoretical maximum amount of ethanol for a given amount of biomass”.

They calculate that a commercial plant could produce 19,000 liters per hectare annually, which is twice as productive as sugar cane-based ethanol and five times as productive as corn. This leads them to the perhaps-optimistic conclusion that “less than three percent of the world’s coastal waters can produce enough seaweed to replace some 60 billion gallons of fossil fuel”.

The chief executive of Berkeley’s Bio Architecture Lab, Daniel Trunfio, says their technique “makes the [seaweed] biomass an economic feedstock for the production of renewable fuels and chemicals”.

The Berkeley researchers worked under grants from the US Department of Energy, InnovaChile, and Norwegian oil company Statoil. The lab currently operates four aquafarming sites in Chile, and hopes to scale up its production towards commercialization over the next three years. ®