Seaweed Study Fuels Bioenergy Enthusiasm

In the February 25 Issue:

Seaweed study fuels bioenergy enthusiasm

Engineered E. coli can convert cell wall component into ethanol

By Rachel Ehrenberg

Web edition : Thursday, January 19th, 2012

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OFFSHORE ENERGYScientists have engineered a bacterium that breaks down seaweed, such as this Macrocystis species, to yield fuels such as ethanol.Bio Architecture Lab Inc.

Seaweed has long made biofuel prospectors drool, but they hadn’t figured out how to efficiently chew through the stuff — until now. Researchers have engineered a bacterium that can break down and digest seaweed’s gummy cell walls to yield ethanol and other useful compounds. If scientists can make the process work at larger scales, seaweed could soon be a serious contender as a source of renewable fuel.

The new research “makes a pretty large leap forward,” says metabolic engineer Hal Alper of the University of Texas at Austin. Unlike corn and many other biofuel feedstocks, seaweed doesn’t need arable land, fertilizer or freshwater. If seaweed can be efficiently munched into ethanol, it broadens the biofuel horizon, says Alper, who was not involved in the research. Seaweed, he says, may be “that new source for unconventional carbon that everyone’s been looking for.”

Scientists from Bio Architecture Lab, a biofuel and renewable chemicals company headquartered in Berkeley, Calif., were interested in creating a biofuel bacterium that is a one-stop shop: They wanted a microbe that could efficiently digest the seaweed cellular building block alginate without pretreatment with chemicals or heat. Alginate is commonly used in ice creams and some textiles, but has proved difficult to break down and metabolize into fuel.

So, led by synthetic biologist Yasuo Yoshikuni, the team took the workhorse bacterium E. coli and within it, patched together the genes and other parts needed for superior seaweed-to-fuel conversion. From the marine bacterium Pseudoalteromonas, the scientists used genes for an enzyme that cuts alginate into smaller molecular bits. The researchers rigged these genes to a cellular transport system already found in E. coli, so the bacterium would secrete the alginate-slicing enzyme into its environment.

Then the team scoured scientific literature and databases for a microbe with serious alginate-digesting machinery. They hit upon the marine microbe Vibrio splendidus, and took a hefty chunk of the Vibrio DNA for use in the E. coli. When the team fed alginate to their engineered E. coli, the microbes pumped out ethanol, the researchers report in the Jan. 20 Science. The system yields 80 percent of the theoretical maximum amount of ethanol for a given amount of biomass, the scientists noted, and with further tweaking will probably be even more efficient.

Part of the beauty of the system is its flexibility, says Yoshikuni. Because the alginate-degrading enzyme is released into the environment, initial breakdown products can easily be harvested for creating useful compounds such as precursors to nylon or plastics. And when E. coli consume the broken-down alginate the bacteria generate a lot of pyruvate, a chemical intermediate useful for making fuels such as butanol or biodiesel.

Seaweed is already harvested at commercial scale in several countries for other uses, and Bio Architecture Lab is working on a pilot plant in Chile to convert seaweed into fuel, says company CEO Daniel Trunfio. Also, any seaweed will do, he notes. “We like to say we’re seaweed agnostic — we can process any brown algae.”

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Comments 8

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It would be great to see corn used primarily for human and animal food again.

Devils advocate: Will there then be protests that man is depleting the oceans of algae?

Daniel Suggs

Jan. 20, 2012 at 9:56am
I've heard of a particular sea weed down in Florida, that's causing problems because it grows so rapidly it clogs canals and drains etc. This would be perfect for the biotec market if it can be used.

theizy

Jan. 20, 2012 at 9:56am
WHAT IF: The bacteria escapes and destroys the ocean's seaweed?

Wayne Johnson

Jan. 23, 2012 at 11:05am
...and what's the plan when this engineered bacterium eventually contaminates the open ocean and begins multiplying exponentially by breaking down "any brown algae" into ethanol? Ever hear of the term, "unintended consequence?"

Steve Palmer

Jan. 23, 2012 at 11:05am
Wonder what would happen if this little critter likes life in the open oceans. I'm not sure if E.coli could survive but, could be an interesting twist, no?

John Sergneri

Jan. 23, 2012 at 11:05am
Great...we engineer a bacterium that breaks down seaweed.....can anybody imagine and accidental introduction of this bacterium into the ocean, endangering all seaweed?

Rodger Hamer

Jan. 23, 2012 at 11:05am
There's pros and cons to every fuel source...this one would just needed to be treated EXTRA cautiously. perhaps level 4 facilities (new ones) would be handling the production and overseeing of bacterium? let's not all bash this idea. it's a great start! with a projected 80% efficiency (sounds almost too good to be true, and beats almost every other source of ethanol) we could be solving the energy crisis within a decade or two more of research.

Nex

Jan. 24, 2012 at 9:19am
Such a fuss! Please note! This group's recombinant strain efficiently digests alginate, not algae.

Alginate is a preparation created from certain brown algae through a number of steps. It has about as much in common with raw algae as corn syrup does with raw maize. In actual algae the "alginic acid" is complexed in elaborate cell walls with cellulose and other protective compounds that would frustrate a recombinant bacterium's appetite. To become alginate it is stewed, strained, attacked with acids and bases and mechanically separated.

For a jargon-free explanation of alginate preparation check cybercolloids.net

John Turner

Jan. 25, 2012 at 9:18am

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