Researchers Isolate Two Enzymes from Termites to Break Up Lignin; Potential Boon to Cellulosic Ethanol
A team of researchers from the University of Florida and the biotechnology company Chesapeake-PERL Inc. of Savage, Md. have isolated two enzymes termites use to break up lignin.
During ethanol production, lignin molecules are clumped around the sugar molecules, forming a barrier the microbes often can’t penetrate; the material must first be exposed to heat and steam or caustic acids and bases to break it down. These extra steps make the process more expensive and often generate hazardous waste. As they report in a paper published online in the journal Insect Biochemistry and Molecular Biology, the researchers determined that enzymes found in termite salivary tissues may be able to accomplish the same task, and at room temperature.
cDNAs encoding two gut laccase isoforms (RfLacA and RfLacB) were sequenced from the termite Reticulitermes flavipes. Phylogenetic analyses comparing translated R. flavipes laccases to 67 others from prokaryotes and eukaryotes indicate that the R. flavipes laccases are evolutionarily unique.
...Both recombinant enzyme preparations showed strong activity towards the lignin monomer sinapinic acid and four other phenolic substrates. By contrast, both isoforms displayed much lower or no activity against four melanin precursors, suggesting that neither isoform is involved in integument formation. Modification of lignin alkali by the recombinant RfLacA preparation was also observed. These findings provide evidence that R. flavipes gut laccases are evolutionarily distinct, host-derived, produced in the salivary gland, secreted into the foregut, bind copper, and play a role in lignocellulose digestion. These findings contribute to a better understanding of termite digestion and gut physiology, and will assist future translational studies that examine the contributions of individual termite enzymes in lignocellulose digestion.
—Coy et al.
The work was funded by the US Department of Energy (DOE) and The Consortium for Plant Biotechnology Research Inc.
A 2009 report by Sandia National Laboratories predicted that cellulosic ethanol could replace about 30% of the nation’s gasoline by 2030, if the price of production could be reduced. (Earlier post.)
This is definitive and original research that could realistically be a significant contribution to green energy. It’s this kind of work that keeps pushing cellulosic ethanol toward practicality.
—James Preston, a UF microbiology professor who studies enzymes in bacteria that break down plant material
The study follows more than two years of work to identify nearly 7,000 genes associated with the termite gut. The researchers are wading through the genes to identify which ones are associated with enzymes that could be useful, and they are hopeful that many more such exciting discoveries are yet to come.
M.R. Coy, T.Z. Salem, J.S. Denton, E.S. Kovaleva, Z. Liu, D.S. Barber, J.H. Campbell, D.C. Davis, G.W. Buchman, D.G. Boucias, M.E. Scharf (2010) Phenol-oxidizing laccases from the termite gut. Insect Biochemistry and Molecular Biology, In Press doi: 10.1016/j.ibmb.2010.07.004