Expression and characterization of recombinant cellulases from an isolated Klebsiella

Abstract

Seven bacteria strains that have a comparable or higher cellulose degrading capability than Cellulomonas fimi were screened out and phylogenetically analyzed. Genes encoding 1,4-endoglucosidase (celJV) and glucoside hydrolase family 8 (celG) were cloned from Klebsiella sp. strain IV-3, and then inserted separately or simultaneously into pET-22b(+), pETDuet-1 (pDin) or pDout that combined pETDuet-1 with the pelB leader. pETDuet-1 expressed these cellulose genes as soluble protein, while other vectors mainly as inclusion bodies. The recombinant enzyme(s) from pDin-JV-G and pDin-JV had the highest degrading capability to CMC-Na, with the degrading zone diameter corresponding to 2.6-and 1.9-fold of Klebsiella sp. strain IV-3, respectively. They also showed the highest degrading capability to filter paper, which corresponded well with the highest specific activity. Even though pDin-JV-G had lower expression efficiency, it still had higher degrading capability than pDin-JV, indicating that enzymatic synergism is helpful for cellulose degradation.