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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Drilling Down to the Nanometer Depths of Leaves for Biofuels

Drilling Down to the Nanometer Depths of Leaves for Biofuels

  4:57:00 PM    Science Lover

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By imaging the cell walls of a zinnia leaf down to the nanometer scale, energy researchers have a better idea about how to turn plants into biofuels.

A xylem cell with fluorescent lignocellulose bands 
as the major feature. (Credit: Image courtesy 
of DOE/Lawrence Livermore National Laboratory)

In a paper appearing online in the journal Plant Physiology, a team from Lawrence Livermore led by Michael Thelen, in collaboration with researchers from Lawrence Berkeley National Lab and the National Renewable Energy Laboratory, has used four different imaging techniques to systematically drill down deep into the cells of Zinnia elegans.

Zinnia is a common garden annual plant with solitary daisy like flower heads on long stems and sandpapery, lace shaped leaves. The leaves of seedlings provide a rich source of single cells that are dark green with chloroplasts and can be cultured in liquid for several days at a time. During the culturing process, the cells change in shape to resemble the tube-like cells that carry water from roots to leaves. Known as xylem, these cells hold the bulk of cellulose and lignin in plants, which are both major targets of recent biofuel research.

Using different microscopy methods, the team was able to visualize single cells in detail, cellular substructures, fine-scale organization of the cell wall, and even chemical composition of single zinnia cells, indicating that they contain an abundance of lignocellulose.

"The basic idea is that cellulose is a polymer of sugars, which if released by enzymes, can be converted into alcohols and other chemicals used in alternative fuel production," Thelen said. "But for this to happen efficiently, we need to find ways to see how this is proceeding at several spatial scales."

To get at the sugars is no easy task. The team had to find ways to overcome the hydrophobic protection of crystalline cellulose provided by lignin in the cell wall. The two polymers, collectively called lignocellulose, are very insoluble, resistant to common chemicals and mechanical breakage, and are a superior substance for providing strength and structure to plants.

The detailed three-dimensional molecular cell wall structure of plants remains poorly understood.

"The capability to image plant cell surfaces at the nanometer scale, together with the corresponding chemical composition, could significantly enhance our understanding of cell wall molecular architecture," said Alex Malkin, a member of the LLNL team who is an expert in atomic force microscopy. "A high resolution structural model is crucial for the successful implementation of new approaches for conversion of biomass to liquid fuels."

To make fuels from plant biomass requires a thorough understanding of the organization of cell walls before determining the best methods for cell wall deconstruction into its components. Catherine Lacayo, a postdoctoral scientist working with Thelen and Malkin, has taken the first steps toward a comprehensive approach.

She came up with techniques that reveal the inner structure of cell walls in these single xylem cells, which represent about 70 percent of the cellulose in plants that can be used in fuel processing. "This approach will be useful for evaluating the responses of plant material to various chemical and enzymatic treatments, and could accelerate the current efforts in lignocellulosic biofuel production."

The research is supported by the Department of Energy Genome Sciences Program through the Office of Biological and Environmental Research, and the DOE's BioEnergy Research Centers in Emeryville and Oak Ridge. It will appear in the September issue of Plant Physiology.

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Bacteria Engineered to Turn Carbon Dioxide Into Liquid Fuel

Bacteria Engineered to Turn Carbon Dioxide Into Liquid Fuel

  10:18:00 AM    Science Lover

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Global climate change has prompted efforts to drastically reduce emissions of carbon dioxide, a greenhouse gas produced by burning fossil fuels.

Genetically engineered strains of the cyanobacterium Synechococcus elongatus in a Petri dish. (Credit: Image courtesy of University of California - Los Angeles)

In a new approach, researchers from the UCLA Henry Samueli School of Engineering and Applied Science have genetically modified a cyanobacterium to consume carbon dioxide and produce the liquid fuel isobutanol, which holds great potential as a gasoline alternative. The reaction is powered directly by energy from sunlight, through photosynthesis.

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