Scientists have discovered a new way to produce ethanol by extracting it directly from seaweed. The discovery offers the potential to generate biofuels that do not compete with terrestrial food production and will not use up scarce freshwater.
Researchers from the Bio Architecture Lab (BAL) in Berkeley, Calif., engineered E. coli bacterium to digest brown seaweed and produce ethanol as a by-product. Kelp grows up to about three feet a day, is abundant in temperate coastal regions and is a type of brown seaweed.
“BAL’s technology to ferment a seaweed feedstock to renewable fuels and chemicals has suggested an entirely new pathway for biofuels development, one that is no longer constrained to terrestrial sources,” said Jonathan Burbaum of the U.S. Department of Energy’s Advanced Research Projects Agency, which helped fund the research. “When fully developed and deployed, large scale seaweed cultivation, combined with BAL’s technology, promises to produce renewable fuels and chemicals without forcing a tradeoff with conventional food crops such as corn or sugarcane.”
Scientists have struggled with producing ethanol from seaweed. The roadblock was alginate, one of four kinds of sugars produced by seaweed. Alginate is a complex polysaccharide and is difficult for microbes to break down. The scientific breakthrough came when the researchers identified a biochemical pathway used by Vibrio splendidus, a marine microbe that feeds on brown seaweed in particular, and inserted the responsible genes into a strain of E. coli. The bacterium was created to convert the seaweed sugars directly into ethanol.
“About 60 percent of the dry biomass of seaweed are fermentable carbohydrates, and approximately half of those are locked in a single carbohydrate alginate,” said Daniel Trunfio, CEO at Bio Architecture Lab. “Our scientists have engineered an enzyme to degrade a pathway to metabolize the alginate, allowing us to utilize all the major sugars in seaweed, which therefore makes the biomass an economical feedstock for the production of renewable fuels and chemicals.”
It is still unclear whether seaweed-based biofuels could have unintended and adverse effects on marine ecology.