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Termites suggest route to new biofuel bioreactors

By Dr Matt Wilkinson , 22-Nov-2007

The quest for more efficient methods of generating biofuels has been boosted by a metagenomic study of the gut bacteria that enable termites to digest wood.

With oil prices constantly rising and forecasts of when oil supplies will run out ever nearing scientists have been searching for efficient ways to turn plants into combustible fuel sources.

 

 

 

One of the major problems with this approach is that the lignin that helps to make plants rigid and able to 'stand upright' interferes with the degradation of the cellulose material that scientists want to turn into fuels such as ethanol.

 

 

 

This means that harsh chemicals or high temperatures are needed to break down the plants before the cellulose can be converted into energy, in contrast termites can devour a wood at a frightening pace.

 

 

 

This latest research, published in today's issue of the journal Nature , by the US Department of Energy Joint Genome Institute (DOE JGI) describes a metagenomic analysis of the bacteria found in termite intestines (flora) and the identification of a variety of genes that code for enzymes that break down the cellulose very efficiently.

 

 

 

"The termite is a remarkable machine and can digest a frightening amount of wood in a very short time, as anyone who has had termites in their house is painfully aware." said Dr Raymond Orbach, Under Secretary for Science, US Department of Energy, whose programme supports DOE JGI.

 

 

 

"Instead of using harsh chemicals or excess heat to do so, termites employ an array of specialized microbes in their hindguts to break down the cell walls of plant material and catalyse the digestion process."

 

 

Metagenomics is the study of the genetic material found in a particular environment, rather than in just one particular species, enabling studies of organisms that cannot be cultured effectively in the laboratory.

 

 

 

The metagenomic shotgun sequencing technique enabled the researchers to study the roles of the termite flora that have hitherto evaded full identification. The sequencing was conducted on an Applied Biosystems PRISM 3730 sequencer using BigDye terminators v3.1.

 

 

 

"Our analysis revealed that the hindgut is dominated by two major bacterial lineages, treponemes and fibrobacters," said co-author Phil Hugenholtz, DOE JGI's Microbial Ecology Program head.

 

 

 

"Treponemes have long been recognised in the termite gut due to their distinctive cork-screw shape, but fibrobacters were an exciting new find, because they have relatives in the cow rumen known to degrade cellulose."

 

 

Microbes belonging to 12 different phyla were found in the termite intestine and these were linked with the enzymes that break down wood, with over 500 genes being linked to the enzymatic deconstruction of cellulose and hemicellulose.

 

 

 

These enzymes were identified using a 'metaproteomic' approach, which were analyzed on a Thermo Fisher Scientific LTQ mass spectrometer after protein extraction and digestion.

 

 

 

"Adapting these findings for an industrial-scale system is far from easy," said Eddy Rubin, JGI Director.

 

 

 

"Termites can efficiently convert milligrams of lignocellulose into fermentable sugars in their tiny bioreactor hindguts. Scaling up this process so that biomass factories can produce biofuels more efficiently and economically is another story. To get there, we must define the set of genes with key functional attributes for the breakdown of cellulose, and this study represents an essential step along that path."

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