Lydia A Ogonda1,2,3, Amélie Saumonneau1, Michel Dion4, Edward K Muge2, Benson M Wamalwa5, Francis J Mulaa2, Charles Tellier6. 1. Université de Nantes, CNRS, UFIP, UMR6286, 2, rue de la Houssinière, 44322, Nantes, France. 2. Department of Biochemistry, School of Medicine, College of Health Sciences, University of Nairobi, P.O BOX 30197-00100, Nairobi, Kenya. 3. Department of Medical Biochemistry, School of Medicine, Masinde Muliro University of Science and Technology, P.O BOX 190-50100, Kakamega, Kenya. 4. Université de Nantes, IRS2, 44000, Nantes, France. 5. Department of Chemistry, School of Physical Sciences, College of Biological and Physical Sciences, University of Nairobi, P.O BOX 30197-00100, Nairobi, Kenya. 6. Université de Nantes, CNRS, UFIP, UMR6286, 2, rue de la Houssinière, 44322, Nantes, France. charles.tellier@univ-nantes.fr.
Abstract
OBJECTIVES: To search for new alkaliphilic cellulases and to improve their efficiency on crystalline cellulose through molecular engineering RESULTS: Two novel cellulases, BpGH9 and BpGH48, from a Bacillus pumilus strain were identified, cloned and biochemically characterized. BpGH9 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. BpGH48 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 BpGH9 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 BpGH9 on crystalline cellulose. CONCLUSIONS: A new alkaliphilic endocellulase BpGH9, was cloned and engineered as a fusion protein (CBM3a-BpGH9), which led to an improved activity on crystalline cellulose.
OBJECTIVES: To search for new alkaliphilic cellulases and to improve their efficiency on crystalline cellulose through molecular engineering RESULTS: Two novel cellulases, BpGH9 and BpGH48, from a Bacillus pumilus strain were identified, cloned and biochemically characterized. BpGH9 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. BpGH48 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 BpGH9 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 BpGH9 on crystalline cellulose. CONCLUSIONS: A new alkaliphilic endocellulase BpGH9, was cloned and engineered as a fusion protein (CBM3a-BpGH9), which led to an improved activity on crystalline cellulose.