Purification and characterization of termite endogenous beta-1,4-endoglucanases produced in Aspergillus oryzae

Although termites are known to have a highly efficient lignocellulose-digesting system, mass production of native endogenous cellulases of termites has failed in Escherchia coli, and in Saccharomyces cerevisiae, and it has not been accomplished. Here we report the successful production, purification, and characterization of two termite endogenous beta-1,4-endoglucanases, RsEG and NtEG, from the salivary gland of Reticulitermes speratus and the midgut of Nasutitermes takasagoensis respectively, using Aspergillus oryzae as host. Thin-layer chromatography analysis showed that both enzymes hydrolyzed the beta-1,4-cellulosic linkage of cellodextrin into cellobiose and glucose. Kinetic studies indicated that the specific activity and Vmax values of the two enzymes were significantly higher than those of previously reported fungal and bacterial endoglucanases.