LAUSR

Objectives To search for new alkaliphilic cellulases and to improve their efficiency on crystalline cellulose through molecular engineering Results Two novel cellulases, Bp GH9 and Bp GH48, from a Bacillus pumilus strain were identified, cloned and biochemically characterized. Bp GH9 is a modular endocellulase belonging to the glycoside hydrolase 9 family (GH9), which contains a catalytic module (GH) and a carbohydrate-binding module belonging to class 3 and subclass c (CBM3c). This enzyme is extremely tolerant to high alkali pH and remains significantly active at pH 10. Bp GH48 is an exocellulase, belonging to the glycoside hydrolase 48 family (GH48) and acts on the reducing end of oligo-β1,4 glucanes. A truncated form of Bp GH9 and a chimeric fusion with an additional CBM3a module was constructed. The deletion of the CBM3c module results in a significant decline in the catalytic activity. However, fusion of CBM3a, although in a non native position, enhanced the activity of Bp GH9 on crystalline cellulose. Conclusions A new alkaliphilic endocellulase Bp GH9, was cloned and engineered as a fusion protein (CBM3a- Bp GH9), which led to an improved activity on crystalline cellulose.