Submitted to: Insect Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/3/2009
Publication Date: 6/1/2010
Citation: Zhang, D., Lax, A.R., Bland, J.M., Yu, J., Federova, N., Nierman, W.C. 2010. Hydrolysis of filter-paper cellulose to glucose by two recombinant endogenous glycosyl hydrolases of Coptotermes formosanus. Insect Science. 17:245-252. Interpretive Summary: The Formosan subterranean termite, Coptotermes formosanus Shiraki, is one of the most destructive and costly wood-feeding insects in many parts of the world. Understanding the wood-degrading enzymes (lignocellulases) residing in the insect is of interest in that it may offer potentials to develop lignocellulase specific biotermiticides and to apply the enzymes for converting plant biomass into biofuel. In this work, we identified and cloned two cellulose-hydrolyzing genes, which are highly expressed (abundant) in the salivary glands of the termite. One of the genes encodes endo-ß-1, 4-glucanase, which cleaves internal cellulose fiber into short glucose chains, and the other encodes ß-glucosidase, which convert the short glucose chain to glucose. Using heterologous expression system, we produced these two enzymes in large quantity in bacterial host E. coli and demonstrated that the bacterial-produced recombinant enzymes could hydrolyze filter-paper cellulose into glucose, a source for ethanol production.
Technical Abstract: Genes encoding for glycosyl hydrolases in multiple families were recovered from an EST library of Coptotermes formosanus, a wood-eating insect. Functional analyses of these genes not only shed light on the mechanisms the insect employs to successfully use cellulosic materials as energy sources, which may serve as strategic targets for designing molecular based bio-pesticides, but also enrich discoveries of new cellulolytic enzymes for conversion of biomass into biofuel. Our study demonstrated that two recombinant endogenous glycosyl hydrolases (endo-ß-1,4 glucanase and ß-glucosidase), expressed in E. coli, could convert cellulose to glucose, a source for ethanol production. Further understanding the mechanisms by which the insects overcome lignin barrier and access the interlocked cellulose in the wood will facilitate industrial process for plant cellulosic ethanol production.