Multiple endo-beta-1,4-glucanase-encoding genes from Bacillus lautus PL236 and characterization of the celB gene

A Bacillus lautus strain was isolated from compost by its ability to degrade microcrystalline Avicel cellulose and acid-swollen cellulose. Three DNA fragments cloned in Escherichia coli encoded at least four endo-beta-1,4-glucanases (EG), of which at least two were contained on one DNA fragment. Another fragment, of 2.5 kb and carrying celB, was cloned in the shuttle-vector plasmid, pJKK3-1, and expressed in E. coli and Bacillus subtilis. The fragment was sequenced and shown to encode a 62-kDa protein, which was found as a 56-kDa mature and active EG in extracts of E. coli and in the supernatant of B. subtilis. The deduced amino acid (aa) sequence has a homology of 37% identical aa on a stretch of 295 aa to EG-E of Clostridium thermocellum. A low level of homology is detected with the Bacillus-type EG.