Worries regarding to the current crisis of climate change and depletion of fossil fuels make the utilization of bioethanol as an attractive option for combating both global warming and less dependence on fossil fuels. Lignocellulose is the most abundant substrate for conversion into fuel. Although cellulosic biomass is difficult to be degraded, it is well-known that termites are efficient decomposers of this material. Since $-glucosidase is essential for cellulose utilization, the aim of this study is to produce, characterize, and compare endogenous $-glucosidases from termites. The enzyme G1NkBG is derived from the salivary glands of the termite Neotermes koshunensis, whereas G1mgNtBG1 is from the midgut of the termite Nasutitermes takasagoensis. The former was successfully expressed in the filamentous fungus Aspergillus oryzae, and the second, in the yeast Pichia pastoris. They were purified to homogeneity from the culture supernatants. The effect of temperature and pH on $-glucosidases activity and stability, as well as the substrate specificities, were studied. Kinetic analyses were also performed. Interestingly, G1NkBG activity was stimulated by glucose, which is an unusual characteristic as a $-glucosidase. G1mgNtBG1 displayed relatively high optimum temperature and thermostability. Both were active on cello-oligosaccharides. Having $-glucosidases with one of these characteristics is very interesting for biotechnological applications, and they can be useful in bioethanol production. Uchima et al., Applied Microbiology and Biotechnology, in press.
Full conference title:
26th Fungal Genetics Conference
- Fungal Genetics Conference 26th (2005)