Cloning and expression of a novel thermostable cellulase from newly isolated Bacillus subtilis strain I15.

A novel bacterial strain with high cellulase activity (2.82 U/ml) was isolated, and then identified by its morphological character and 16S rRNA sequence, and named Bacillus subtilis strain I15. The extracellular thermostable cellulase exhibited the maximum activity at 60 degrees C and pH 6.0. It was very stable since more than 90% of original CMCase activity was maintained at 65 degrees C after incubation for 2 h. The cellulase gene, celI15, was cloned and extracellularly expressed by Escherichia coli BL21 (DE3), which encoded the extracellular protein of about 52 kDa. The extracellular activity of CelI15 from E. coli BL21 was up to about 6.78 U/ml, and all the other properties were almost the same as that from the wild-type strain.