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Researchers Identify Enzyme That Breaks Down Chitin; May Lead to Cheaper Biofuels

14 October 2010

Researchers from the Norwegian University of Life Sciences (UMB) have identified an enzyme that can help to break down recalcitrant crystalline polysaccharides such as cellulose and chitin. In a paper in the 8 Oct. issue of the journal Science, the team describes an enzyme that acts on the surface of crystalline chitin, where it introduces chain breaks and generates oxidized chain ends, thus promoting further degradation by chitinases.

The team also found strong indications that similar enzymes exist that work on cellulose. The findings not only demonstrate the existence of a hitherto unknown enzyme activity but also provide new pathways toward more efficient enzymatic conversion of biomass for use in the production of biofuels and biopolymers.

In theory it’s easy to convert the carbohydrates in cellulose, for instance, to small sugar molecules that nourish microorganisms which in turn produce methane and ethanol. But in practice, it has proven to be quite challenging.

—Dr. Gustav Vaaje-Kolstad, Norwegian University of Life Sciences

The respective carbohydrate polymers of both chitin and cellulose form extremely dense, resilient bonds. Indeed, the biological function of chitin and cellulose is precisely to make the organism physically hard and durable—slowing the breakdown rate for enzymes whose function is to decompose these kinds of material.

Earlier work by members of the team found that microorganisms that break down chitin produce a protein that increases substrate accessibility and potentiates hydrolytic enzymes. These proteins are classified as carbohydrate-binding modules (CBMs). The first example of such a protein is CBP21 (CBP for chitin-binding protein), produced by the chitinolytic bacterium Serratia marcescens.

We show here that CBP21 is an enzyme that catalyzes cleavage of glycosidic bonds in crystalline chitin, thus opening up the inaccessible polysaccharide material for hydrolysis by normal glycoside hydrolases...In the presence of a reductant such as ascorbic acid, CBP21 boosted chitinase efficiency to much higher levels than previously observed. Biotechnological applications could take advantage of the ability to increase CBP21 activity by adjusting the reaction conditions.

...the reaction catalyzed by CBP21 comprises a hydrolytic step and an oxidation step. We suggest naming CBP21 a “chitin oxidohydrolase.”

—Vaaje-Kolstad et al.

To function, the enzymes must be designed to attach securely to the crystalline glucose chains they are intended to break down. This allows them to split the sugars repeatedly without falling off.

Oxidohydrolases could make it both less costly and easier to produce biofuel. They could also serve to scale back the practice of using edible plants as feedstock. The UMB researchers have applied for a patent on their method and are discussing further collaboration with the international enzyme producer Novozymes.

The Research Council of Norway has funded this research through several sources, including the open competitive arena for independent, researcher-initiated basic research projects (FRIPRO) and the research programs on Basic Industry-oriented Biotechnology (GNBIO - terminated), Clean Energy for the Future (RENERGI), and Nature-based Industry (NATUROGNAERING).

Resources

  • Gustav Vaaje-Kolstad, Bjørge Westereng, Svein J. Horn, Zhanliang Liu, Hong Zhai, Morten Sørlie, Vincent G. H. Eijsink (2010) An Oxidative Enzyme Boosting the Enzymatic Conversion of Recalcitrant Polysaccharides. Science Vol. 330. no. 6001, pp. 219 - 222 doi: 10.1126/science.1192231

October 14, 2010 in Biomass, Catalysts, Enzymes | Permalink | Comments (6) | TrackBack (0)

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The price of edible food stocks has been going up at an accelerated rate since the world started to use food stocks to produce ethanol. In many cases the rise has been over 50% in the last three year.

If this trend is not reversed soon, many more will go hungry as food price keeps going up. Using edible food to produce liquid fuels for our gas guzzlers is one of the worse decision our leaders and business community have taken in the last few centuries.

Using non-food stocks seems to be a better idea but there again the long term effects may not be that good. Our essential forests may quickly disappear the way they did in Haiti if it is left entirely in the hands of the business community.

Replacing polluting liquid fuels with clean electricity is a much better idea. Government support should be redirected towards those technologies and quickly removed from liquid fuel production.

I kinda like the idea of powering my VW with beetles.

Mister Harvey you should look at the number to see that only half of the liquid fuel are used for passenger car the rest is used for truck airplane agriculture machine building machine boating etc. Even in the best of the electric world we won't be able to power a truck or an aircraft with battery before long. So investment in liquid fuel will continue, and I don't think that electric car will become the mainstream of passenger car before long. Last but not least rotational crop, use of stem instead of grain, reducing the amount of beef in our diet (I said beef not meat) could significantly reduced the required surface to feed populations, 80% of the food we grow is to feed animals. I we were eating rabbit, chicken,cat fish and Wallabies instead of beef, porc and lamb, not only our energy and land use would shrink but also our emission of green house gas would to. Cherry on the cake, shifting too fast on electric cars would increase our CO2 footprint as long as most of the electricity will be made out of coal. There is not fast solution to change that.

Harvey, these enymes transform uneatable biomass into eatable. Plant waste material (of classical agriculture or forestry) can be transformed into sugar, which can be fed to animals or further fermented to proteins.

The increase of food prices was mostly a result of increased energy prises, and increased demand of food. Use of food to produce fuel was only of minor importance.

Anyway, look at the demographic and economical evolution in the world. It is absolutelty clear that we are heading to ever more and dramatically more severe food crises if we dont have a paradygm shift in food production. Eating less or different meat is an important first step but it will by far not be enough. We absolutely need a biotechnological revolution to make food and protein production multiple times more efficient and non-poluting. Thanks to the investments in biofuel production, this will happen.

It is much more easy to produce durable cellulosic biomass than biomass via classical agriculture. Additionally, the productivity per acre is multiple times that of starches.

If there is one thing we desperately need to save the planet, it is a biotechnology revolution in food production. Simply look at the numbers. Food demand is riding an exponential function that is still far from slowing down. With a majority of the world population craving for more and better food, the recent food crises were only a shadow of what is to come.

We can only hope biotechnology can provide that food before the last rainforest is burnt down to produce soya.
This blessed energy crisis is exactly what was needed to invest in these technologies.

If the real honest intent is to produce more edible food without degradation to productive farm land it would make sense. However, this is not the prime purpose. The driver here is to produce more liquid fuel with minor food production as side/secondary effect as a project selling point.

A 4-tonne gas guzzler requires (eats) 5 to 10 times the energy than one average human. Earth can, with proper management, feed 10 to 15 billion people or 2 to 3 billion gas guzzlers, but not both.

We will have a choice to make i.e. limit human population or limit the energy crop diverted to gas guzzlers..

Of course, human could eat less beef and more chicken meat which can be produced with 4 times less food energy but we are not (yet) ready to do so. Extended financial crisis (like the current one) may help to modify some of our acquired addictions.

Of course, we will develop more efficient crops and farming methods to the level required to feed something between 10 and 15 billion people in a few centuries down the line. Eventually, transforming sun energy into edible products should be possible. By that time, ICE will be out of use for a long time and liquid fuels may no longer be required.

TT: Yes, our beef eating addiction is a very expensive way to feed ourselves. The average cattle is less than 9% efficient as an energy transformer. It is still affordable because we have more than enough farming land. Chickens are about 4 times as efficient as cattle. A switch from beef to chicken burgers, chicken hotdogs, chicken pizza & pasta etc could liberate a few million hectares and reduce GHG. This may be what we will have to do when more farm land is used to produce liquid fuels for our gas guzzlers.

Asians eat many times more chicken meat than beef. The reason is simple, they have a much higher population but don't have enough farm land to produce beef at the per capita level we do.

Very few countries have enough excess farm land to produce liquid fuel and keep their population well fed at the same time.

Imagine USA with 1.3 million people to feed. Not much corn would be transformed into ethanol and our beef per capita consumption would forcibly be way down.

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