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, 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 search for enzymes that break down lignocellulosic biomass and can be mass-produced is perhaps the most critical task undertaken by biotechnologists. They are looking to the digestive ecosystems of ruminants and termites, both of which contain enzymes that efficiently break down plant cell walls. Once efficient enzymes are available in large quantities, potential ethanol feedstocks expand beyond starch-based crops like corn and sugar to the entire class of cellulosic plants, including grasses, trees, and shrubs.
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