The microorganism hydrolyzing carboxymethylcellulose (CMC) was isolated from seawater, identified as Bacillus subtilis subsp. subtilis by analyses of 16S rDNA and partial sequences of the gyrA gene, and named as B. subtilis subsp. subtilis A-53. The molecular weight of the purified carboxymethylcellulase (CMCase) was estimated to be about 56 kDa with the analysis of SDS-PAGE. The purified CMCase hydrolyzed carboxymethylcellulose (CMC), cellobiose, filter paper, and xylan, but not avicel, cellulose and p-nitrophenyl-beta-D-glucospyranoside (PNPG). Optimal temperature and pH for the CMCase activity were determined to be 50 degrees C and 6.5 respectively. More than 70% of original CMCase activity was maintained at relative low temperature ranging from 20 to 40 degrees C after 24h incubation at 50 degrees C. the CMCase activity was enhanced by EDTA and some metal ions in order of EDTA, K+, Ni2+, Sr2+, Pb2+, and Mn2+, but inhibited by Co2+ and Hg2+. (C) 2009 Elsevier Inc. All rights reserved