Seaweed set to ignite biofuel boom
Already a major contributor to the food and fertiliser industries, seaweed could also hold the key to low cost biofuels thanks to the creation of an algae-eating strain of E. coli.
Writing in Science, Adam Wargacki and his colleagues from the US-based company BAL, which stands for Bio Architecture Lab, have developed a modified form of the E. coli bacterium capable of unlocking the chemical energy stored inside seaweeds and turning it into ethanol.
In tests, their re-engineered bugs work with an efficiency of over 80% and are able to generate alcohol concentrations on par with processes currently used to produce bioethanol from arable crop waste.
The major hurdle the team needed to overcome is the fact that, in seaweed, a large amount of the energy is stored in the form of a complex sugar called alginate, which is difficult for individual bacterial strains to break down, let alone ferment to alcohol.
To engineer a seafood-favouring form of E. coli, the BAL team "borrowed" genes from other organisms and used them to "tool up" their new bug strain. These included adding a secretable Pseudoalteromonas "alginate lyase", which breaks up the seaweed alginates into smaller, more-digestible fragments, and a family of genes, from a water-borne bug called Vibrio splendidus, that transport these alginates into the bacteria and then break them down.
Set to work on a diet of the common brown seaweed Saccharina japonica, the engineered E. coli yielded alcohol concentrations of 4.7% within 48 hours. Exploiting seaweed in this way offers major advantages over traditional approaches to biofuel production.
Feasibility studies have suggested that each hectare of sea would yield a dry-weight of 59 tonnes per year, which could produce as much as 19,000 litres of bioethanol, which is twice what cane can do and five times the yield achieved from maize.
And as the team point out, seaweed aquaculture would not require arable land and therefore would not impact on food production, it doesn't require fertilisers and may even help to decontaminate nitrogen-polluted water and, even more critically, this form of farming does not require irrigation!