Termites' Digestive System Could Act as Biofuel Refinery

Termites' Digestive System Could Act as Biofuel Refinery

  10:02:00 AM    Science Lover

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One of the peskiest household pests, while disastrous to homes, could prove to be a boon for cars, according to a Purdue University study.

Mike Scharf's work with termites has shown that the insects' digestive systems may help break down woody biomass for biofuel production. (Credit: Purdue Agricultural Communication photo/Tom Campbell)

Mike Scharf, the O. Wayne Rollins/Orkin Chair in Molecular Physiology and Urban Entomology, said his laboratory has discovered a cocktail of enzymes from the guts of termites that may be better at getting around the barriers that inhibit fuel production from woody biomass. The Scharf Laboratory found that enzymes in termite guts are instrumental in the insects' ability to break down the wood they eat.

The findings, published in the early online version of the journal PLoS One, are the first to measure the sugar output from enzymes created by the termites themselves and the output from symbionts, small protozoa that live in termite guts and aid in digestion of woody material.

"For the most part, people have overlooked the host termite as a source of enzymes that could be used in the production of biofuels. For a long time it was thought that the symbionts were solely responsible for digestion," Scharf said. "Certainly the symbionts do a lot, but what we've shown is that the host produces enzymes that work in synergy with the enzymes produced by those symbionts. When you combine the functions of the host enzymes with the symbionts, it's like one plus one equals four."

Scharf and his research partners separated the termite guts, testing portions that did and did not contain symbionts on sawdust to measure the sugars created.



Once the enzymes were identified, Scharf and his team worked with Chesapeake Perl, a protein production company in Maryland, to create synthetic versions. The genes responsible for creating the enzymes were inserted into a virus and fed to caterpillars, which then produce large amounts of the enzymes. Tests showed that the synthetic versions of the host termite enzymes also were very effective at releasing sugar from the biomass.

They found that the three synthetic enzymes function on different parts of the biomass.

Two enzymes are responsible for the release of glucose and pentose, two different sugars. The other enzyme breaks down lignin, the rigid compound that makes up plant cell walls.

Lignin is one of the most significant barriers that blocks the access to sugars contained in biomass. Scharf said it's possible that the enzymes derived from termites and their symbionts, as well as synthetic versions, could be more effective at removing that lignin barrier.

Sugars from plant material are essential to creating biofuels. Those sugars are fermented to make products such as ethanol.

"We've found a cocktail of enzymes that create sugars from wood," Scharf said. "We were also able to see for the first time that the host and the symbionts can synergistically produce these sugars."

Next, Scharf said his laboratory and collaborators would work on identifying the symbiont enzymes that could be combined with termite enzymes to release the greatest amount of sugars from woody material. Combining those enzymes would increase the amount of biofuel that should be available from biomass.

The U.S. Department of Energy and Chesapeake Perl funded the research.

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A novel enzymatic catalyst for biodiesel production

A novel enzymatic catalyst for biodiesel production

  4:47:00 PM    Science Lover

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Continuous production of biodiesel can now be envisaged thanks to a novel catalyst developed by a French team at CNRS's Centre de Recherches Paul Pascal (CRPP). The results, which have been patented, have just been published in the journal Energy & Environmental Science.

Diagram showing the enzyme biocatalytic reactor and its unidirectional continuous flow operation that uses enzymatic catalysis to turn triesters into biodiesel. © CNRS

Biofuel production provides an alternative to fossil fuels. Biodiesels, for instance, are processed products based on oils from oleaginous plants such as oilseed rape, palm, sunflower and soybeans. They result from a chemical reaction, catalyzed in either an acidic or preferably a basic medium, between a vegetable oil (90%) and an alcohol (10%). This reaction, known as transesterification, converts the mixture into a methyl ester (the main constituent of biodiesel) and glycerol. A saponification side reaction (methyl ester conversion into the corresponding acid salt) reduces methyl ester yield. To increase the yield, it was therefore necessary to develop alternative catalysts.

For this type of reaction, certain enzymatic catalysts such as those belonging to the family of lipases (triglyceride hydrolases) are particularly efficient and selective. However, their high cost and low conformational stability restrict their industrial use, unless they can be irreversibly confined in porous matrices, allowing good accessibility and enhanced mass transport. This has now been achieved by the team led by Professor Renal Backov.



In an initial study, they had already demonstrated the possibility of efficient catalysis, by developing modified silica-based cellular matrices that make it possible to confine lipases in order to obtain exceptional yields for hydrolysis, esterification and transesterification reactions. Their work had also shown that unpurified enzymes could be used in the matrices. The fact that they were unpurified was a first step to significantly reducing the cost of biocatalysts. However, the methodology did not allow continuous biodiesel production. This obstacle has now been overcome.

Researchers have developed a new method that generates the cellular hybrid biocatalyst in situ inside a chromotography column. This novel approach makes it possible to carry out continuous, unidirectional flow synthesis over long periods, since catalytic activity and ethyl ester production are maintained at high, practically steady levels during a two-month period of time. These results are amongst the best ever obtained in this field.

Research is continuing into solvent-free conversion of triesters, aimed at minimizing waste production and curbing the use of solvents and metals in chemical transformation processes. This work, which meets current energy and environmental requirements, shows how much chemists are working in the public interest, and confirms the importance of integrative chemistry.

More information: References:

-- “Enzyme-Based Biohybrid Foams Designed for Continuous Flow Heterogeneous Catalysis and Biodiesel Production”, N.Brun, A.Babeau-Garcia, M.-F.Achard, C.Sanchez, F.Durand, L.Guillaume, M.Birot, H.Deleuze and R.Backov - Energy & Environmental Science, 2011 DOI:10.1039/C1EE01295A

-- Catalyseur enzymatique hétérogène, procédé de préparation et utilisation pour la catalyse enzymatique en flux continu. N.Brun, H.Deleuze, C.Sanchez and R.Backov. French patent 2010. File number FR10-56099. Provided by CNRS

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Fungus Genes Help Turn Grass into Ethanol Modified yeast could help make ethanol from hard-to-digest materials.

Fungus Genes Help Turn Grass into Ethanol Modified yeast could help make ethanol from hard-to-digest materials.

  10:37:00 PM    Science Lover

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Genes copied from a common fungus could simplify the production of ethanol from abundant materials such as grass and wood chips, a development that could one day help ethanol compete with gasoline.

Scientists have taken genes from a fungus that grows on grass and dead plants, and transplanted them into yeast that is already used to turn sugar into ethanol. The genes let the yeast ferment parts of plants that it normally can't digest, potentially streamlining the production of ethanol.

The transporters: Fungus proteins
that help transport complex sugars for
digestion can be seen in this image of
yeast. The transporter proteins have
been tagged with a green fluorescent
protein.Credit: Jamie Cate and Susan
Jenkins, UC Berkeley

"It's just a more efficient process," says Jamie Cate, a biologist at the University of California, Berkeley and at Lawrence Berkeley National Laboratory. "Shaving off every dime that you can could make it compete with oil," says Cate, who led the work.

Most ethanol is produced using simple sugars, like the glucose derived from corn kernels or sugar cane. Ethanol producers would like to use glucose from more abundant sources, such as corn husks and stalks, switchgrass, wood waste, and other tough plant materials. But those plant parts are made of cellulose, a carbohydrate built from long chains of sugars. For yeast to produce ethanol from these materials, the complex carbohydrate has to first be broken down into very simple sugars, a process that takes time and normally requires the addition of expensive enzymes.

With the new technique, ethanol makers would no longer have to break cellulose down into simple sugars. Instead, they would only need to break down cellulose into an intermediate material called cellodextrin. The modified yeast can work with this, instead of waiting for it to be broken down all the way to glucose, removing steps that cost time and money.

Yeast takes a simple molecule such as glucose and digests it as food, producing alcohol as a by-product. The Berkeley researchers, along with a colleague from the Chinese Academy of Sciences in Tianjin, found that a fuzzy orange fungus called Neospora crassa that grows on dead plant matter produces two different proteins that help transport more complex cellulose molecules into cells for digestion. In addition, they found that the fungus produces an enzyme that can help further break down those molecules. The researchers then pored through the genome of a Neospora crassa to find the genes responsible for these abilities

Lee Lynd, an environmental engineer at Dartmouth, says the concept of engineering sugar-fermenting microbes so they'll also produce enzymes "is widely regarded as the most promising approach" for converting cellulosic materials into ethanol. Many researchers are working on consolidating ethanol processing steps, he says, and some have achieved better results in some parts of the process. But Lynd says this is the first time, as far as he knows, that someone has cloned these transporters.

"These advances are relevant, demonstrate in principle the promise of engineering microbes for improved biomass processing, and could be applied commercially," Lynd says. "However, the advances are not enabling by themselves, and represent a relatively early step on a long path."

The technique doesn't address much of the processing involved in ethanol production. Ethanol makers would still need to use enzymes to break the cellulose down to an intermediate stage called cellodextrin. But the yeast can work with this, instead of waiting for it to be broken down all the way to glucose, removing steps that cost time and money.

For their research, the group used a strain of yeast commonly studied in laboratories. The genes will have to be inserted into strains bred to withstand the demands of industrial ethanol production. Scientists at the University of Illinois, part of the Energy Biosciences Institute that funded the research, will work on that. Meanwhile, Cate will continue to study Neospora to see if he can find an even better combination of genes. "We're still going to be poking and prodding at Neospora to see what other tricks it might have for us," he says.

It could be five years before the modified yeast is ready for use in a demonstration-scale ethanol plant, and perhaps a decade before ethanol made this way winds up in gas tanks, Cate says. Researchers won't know for some time how much of a boost in yield the modified yeast will produce until it is tried in a production setting.

"We make a 10 to 20 percent improvement, other companies make a 10 to 20 percent improvement in their enzymes, and all of a sudden we've brought down the cost to where it can start to be competitive with oil," says Cate.

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