Purification and characterization of cellulase produced by Bacillus amyoliquefaciens DL-3 utilizing rice hull

A microorganism hydrolyzing rice hull was isolated from soil and identified as Bacillus amyloliquefaciens by analysis of 16S rDNA and partial sequences of the gyrA gene, and named as B. amyloliquefaciens DL-3. With the analysis of SDS–PAGE, the molecular weight of the purified cellulase was estimated to be 54 kDa. The purified cellulase hydrolyzed avicel, caboxymethylcellulose (CMC), cellobiose, β-glucan and xylan, but not p-Nitrophenyl-β-d-glucopyranoside (PNPG). Optimum temperature and pH for the CMCase activity of the purified cellulase were found to be 50 °C and pH 7.0, respectively. The CMCase activity was inhibited by some metal ions, N-bromosuccinimide and EDTA in the order of Hg2+ > EDTA > Mn2+ > N-bromosuccinimide > Ni2+ > Pb2+ > Sr2+ > Co2+ > K+. The open reading frame of the cellulase from B. amyloliquefaciens DL-3 was found to encode a protein of 499 amino acids. The deduced amino acid sequence of the cellulase from B. amyloliquefaciens DL-3 showed high identity to cellulases from other Bacillus species, a modular structure containing a catalytic domain of the glycoside hydrolase family 5 (GH5), and a cellulose-binding module type 3 (CBM3).