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March/April 2008

TR10: Cellulolytic Enzymes

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By Alexandra M. Goho

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Her latest strategy is a computational approach that can rapidly identify thousands of new protein sequences for screening. This approach generates many more sequence variants than other methods do, greatly increasing the chances of creating functional molecules with useful new properties.

Arnold is using the technique to build libraries containing thousands of new cellulase genes. She and her colleagues will then screen the cellulases to see how they act as part of a mixture of enzymes. "If you test them simply by themselves, you really don't know how they work as a group," she says.

To fulfill her ultimate goal of a superbug able to feed on cellulose and produce biofuels, Arnold is working with James Liao, a professor of chemical engineering at the University of California, Los Angeles. Liao recently engineered E. coli that can efficiently convert sugar into butanol, a higher-energy biofuel than ethanol. Arnold hopes to be able to incorporate her new enzymes into Liao's ­butanol-­producing microbes. Gevo, a startup cofounded by Arnold and based in Denver, CO, has licensed Liao's technology for use in the large-scale production of advanced biofuels, including butanol.

Overcoming cellulose's natural resistance to being broken down is "one of the most challenging protein-engineering problems around," says Arnold. Solving it will help determine whether low-­emission biofuels will ever be a viable substitute for fossil fuels.

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Comments

  • Superbugs
    mkogrady on 02/19/2008 at 3:09 PM
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    Are the superbugs, as described in the article, only found in fungi? What about termite bellies, carpenter ant bellies, woodland critters living in the decomposing masses of leaves and twigs, or grasses found in nature? I would suspect that a superbug capable of digesting or consuming woody materials will be found in woods - while a different critter that digests grassy materials will live in prairie environments. I would even bet that a good field biologist could find some simliar bugs living in waterways or bog like areas where leave, twigs and grasses would be delivered via a stream of water.

    Nature has been feeding itself for ions, are we trying to reinvent the wheel or just increase the effciency?
    Rate this comment: 12345
    • Re: Superbugs
      ronwagn on 02/20/2008 at 6:43 AM
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      I have wondered why they don't just combine some termites with all the cellulose and let them do their business. Then process the resultant mess, and save some to start the next batch. I wonder if this has been tried. I understand that their is a Southern type of termite that is much more active than the Northern type.

      I do fear that we might genetically produce some organism that will destroy live plants in the environment on a large scale. I am pretty sure we have no oversight on this possibility. Do a search on grey goo. Grey goo is the scenario where nanotechnology destroys all living things.
      Rate this comment: 12345
      • Re: Superbugs
        jgillece on 02/20/2008 at 11:50 AM
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        Regarding termites and cellulose, look here...

        http://www.wired.com/science/planetearth/magazine/15-10/ff_plant?currentPage=4
        Rate this comment: 12345
        • Re: Superbugs
          mkogrady on 02/29/2008 at 2:35 PM
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          Read it before. As I indicated, perhaps a superbug that is specific to a particular food source has better enzymes in it's gut to digest the local foods. The south american termites may be best for digesting jungle-chow, while another variety (maybe african plains) may be better suited to chomping on grassy materials. Get these two together, legally married and have some offspring that may not care where the food source comes from because they can feed on any variety of biomass.

          my 2 cents
          mko
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  • cellulolytic enzymes
    devassocx on 02/20/2008 at 1:25 AM
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    the article states that when fully exploited
    cellulose ethanol will significantly reduce the
    usage of gasoline.

    From what I have read 'significant' is less than
    3.5% of our gasoline usage. I don't see this as
    significant.

    The only thing significant is the terrific increase in food prices that has resulted from
    using corn to make ethanol. Typical gov't
    action.
    Rate this comment: 12345
    • Re: cellulolytic enzymes
      ronwagn on 02/20/2008 at 6:30 AM
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      Butanol can be mixed with gasoline in high percentages. It is about equal to gasoline in energy, and can be shipped in pipelines.It can also be used to produce electricity. Cellulosic ethanol production does not use grain. Anyway corn is mainly used to feed animals, as in "corn fed beef." Let the cattle eat grass. They will be a lot happier than stuck in a stall. Plus we eat too much meat for our health anyway. Also, obesity is the worlds largest health problem, not malnutrition.
      Rate this comment: 12345
      • Re: cellulolytic enzymes
        martinaatayo on 02/20/2008 at 8:46 PM
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        Good work on the part of the professor. But long term sustainability of both microbial and enzymatic bioreactants culturing and nurturing,absolutely essential for fermentation
        in the methodology, fermentation process time
        factor itself to achieve desired large scale industrial product commensurate to daily user demand, comparable to existing classical thermal petro-chemical/petroleum product synthesis, even on readily availability of basic
        raw materials, raises doubts on this process'
        potential to eventually replace industrail scale fuel energy in today's world. very good but to keenly follow the progress. 
        Rate this comment: 12345
    • Re: cellulolytic enzymes
      MakeSense on 02/21/2008 at 9:46 AM
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      The math is simple, but the media always resorts to terms like "significant." In 2022, the U.S. is expected to consume the equivalent of 170 billion gallons of gasoline. 36 billion gallons of ethanol is the equivalent of 23 billion gallons of gasoline, making that amount 13.5% of automobile fuel. NOTE: We currently use about 145 billion gallons, so the ethanol will not even account for the expected increase by 2022, meaning we will use more gasoline in 2022 than we do today. Is this "significant"? Gasoline accounts for about 43% of our oil consumption, meaning that in 2022, that amount of ethanol would amount to the equivalent of about 6% of our oil. Is that significant in light of the fact that we will use 15% more oil in 2022 than we do today? It takes energy to make ethanol. Most of that 36 billion gallons will be corn ethanol, which basically breaks even on energy. This cuts into those percentages, I would say "significantly."
      Rate this comment: 12345
      • Re: cellulolytic enzymes
        deep on 02/25/2008 at 3:46 AM
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        The media may be wrong in the way it calculates ethanol percentages.But the  impact of biofuels on food price will actually influence the way people spend.Food price rise is not a bad thing as many people seem to suggest.Infact food prices have remained low for too long a time ,which has resulted in poverty becoming a permanent feature for those involved in agriculture in developing countries.The macro effect of biofuels as i see it is competition of acreage between crops , high food price which forces people to opt for more fuel efficent vehicles.This shift is already visible with fall in the no of SUVs sold and niche vehicles like hybrids becoming mainstream.The net effect is a fall in gasoline consumption as people will have to make more provision for basic needs like food.
        Rate this comment: 12345
      • Re: cellulolytic enzymes
        Scottar on 03/10/2008 at 12:01 AM
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        Now I'm not doubting your claim that ethanol is a break even fuel but DOE claims that: "Each gallon of corn ethanol today delivers as much as 67% more energy than is used to produce it."

        http://www1.eere.energy.gov/biomass/ethanol_myths_facts.html

        So I can only wonder where DOE gets it's input from?
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    • Re: cellulolytic enzymes
      ronwagn on 03/10/2008 at 1:28 PM
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      You are totally contradicting yourself. Cellulosic ethanol will replace food based ethanol. Why not help promote a positive solution, rather than curse the darkness.
      Rate this comment: 12345
  • Dangerous
    Gcanno on 02/25/2008 at 3:53 AM
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    Is there any way this can throw the earth's biological balance off. if you alter these enzymes can they mutate and destroy our food source.

    The Definition of an expert is a person that avoids all the little mistakes on the way to the big fallacy.

    Pete Seeger
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    • Re: Dangerous
      ronwagn on 03/10/2008 at 1:30 PM
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      Who knows. Nobody is looking at this, as far as I know. The EPA seems to be brain dead.
      Rate this comment: 12345
  • bio-fuels
    Arachnid on 03/09/2008 at 10:56 AM
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    If obesity is more of a problem than malnutrition, then let's improve the technology for liposuction and convert the fat into bio-fuel, thus solving two problems at once.
    Rate this comment: 12345
    • Re: bio-fuels
      mkogrady on 03/19/2008 at 3:26 PM
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      THIS WILL MAKE AN EXCELLENT BUMPER STICKER!
      Rate this comment: 12345
  • [no subject]
    skipcjr on 03/16/2008 at 7:24 PM
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    this is the way to go..........
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  • Food Prices
    terrys122 on 03/19/2008 at 5:50 PM
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    Mexico has been hit particularly hard due to rising corn prices.  This will not increase the standard of living for third world countries.  In fact, third word countries will remain poor for a longer period of time because they won't be able to make the transition to an industrial based economy.  This transition is the only real way of bringing people out of poverty because more people  can move out of agriculture and into manufacturing jobs.
    Rate this comment: 12345
  • Not So Top 10
    anorlunda on 06/22/2008 at 4:31 PM
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    I find this whole top 10 list disappointing.  There must be thousands of science news items every day equally exciting.  One could randomly pick 10 of them to make a list of equal quality to TR's top 10.   I think that a more accurate title for this list would be "10 Of The Top Million Exciting Ideas Being Worked On"

    In order for an item to be "likely to affect our lives in the future", it must not only have great promise if successful, it must be highly likely to succeed in the research, development, production, deployment and competition phase of a life cycle.  Anything in preliminary or in the early stages should be disqualified.

    Disagree?  Just think of all the exciting ideas in the past 40 years for technologies that promised to displace silicon as king of the hill in electronics.   There must have been 2 or 3 such exciting preliminary ideas every year.

    If TR wanted to make this top 10 list truly significant and respected, it should make the selection process transparent, or open it up to peer voting on the web.  Perhaps a wiki on "Top 10" might be the way to go.
    Rate this comment: 12345
  • More efficient to just burn it?
    jpdemers on 11/10/2008 at 11:11 PM
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    If one were to just burn the cellulose in a power plant, and use the electricity to recharge plug-in electric or hybrid vehicles, how would that compare to the fermentation->butanol->interal combustion engine route, in terms of vehicle miles per ton of biomass? 
    Rate this comment: 12345
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