Termites may provide the key to breaking down woody biomass for more efficient biofuel production.

A team from Purdue University in West Lafayette, USA, is using enzymes from the gut environment of termites to improve processes for the saccharification of second-generation feedstocks.

Lead researcher Michael Scharf explains that current biofuel production processes require a lot of energy, which adds significant costs to second generation ethanol production.

‘The market needs lignin-degrading technology that operates at ambient temperatures and does not generate hazardous waste. Technology that can meet these needs has the potential to reduce processing costs and make ethanol more viable in the market.’

According to Scharf, current biorefinery pretreatment operations use heat and/or alkalinity to break lignin, solubilise hemicellulose and isolate cellulose. The team uses a cocktail of termite-derived enzymes to combine the three steps into a single pretreatment and saccharification process, and reduce the need for heat, energy and alkalinity.

The group has created synthetic ‘recombitant’ enzymes produced out of genes sampled from host termite tissues. To achieve this, the termites graze on pine sawdust in 10-24 hour incubations. These enzymes include two cellulases that act on cellulose and hemicellulose, and a laccase that acts on lignin.

‘The laccase acts on lignin and the two cellulases display a high level of collaboration in simple sugar release (~300-fold synergy),’ alleges Scharf.

Termites were chosen because their digestive tissues boast a complex cocktail of apparent cellulase and lignin degrading enzymes. Termite symbionts are also said to produce a rich complement of cellulases and related enzymes.

The scientists have collaborated with protein production company Chesapeake Pearl, based in Maryland, USA, to create the synthetic enzymes. The termite genes responsible for creating the enzymes are inserted into a virus and are then fed to caterpillars, which act as ‘biological machinery’ to produce large amounts of the recombinant enzymes. Another insect was chosen because the recombinant enzymes are said to have a high probability of being correctly folded and processed.

While the researchers have been encouraged by results at ‘test-tube level’, Scharf notes, ‘We have not yet developed any commercial technology, so we cannot comment on efficiencies at the bioreactor level. Our goals up to this point have been to understand how termites and their symbionts accomplish lignocellulose digestion, and to identify leads for further development.’

Choosing the most important genes and enzymes to pursue from the hundreds available remains a challenge, says Scharf. As such, the team intends to conduct controlled, hypothesis-driven research to determine which enzymes are the most viable candidates.

Dr. Simon Cragg, of the School of Biological Sciences in the University of Portsmouth, UK, says, ‘If successful, this approach would release simple sugars for which we already have centuries of development in the technology for generation of alcohols. Thus, a rather unpromising material such as straw can be converted to a liquid fuel. While we already have a wide range of renewable energy technologies for supplying fixed installations, we have fewer options for transport. This technology could help fill this gap.’

While complimentary of the study, Cragg notes, ‘There is much to be done to bring the insights generated to the point where pricecompetitive fuel is generated. Particularly challenging problems for developing these ideas lie in the question of economically viable feedstock processing and transportation. Before enzymatic degradation, feedstocks will almost certainly require reduction to easilydigested particles, which demands significant energy input. Parallel engineering efforts are therefore needed to make a step change in the efficiency of processing.’