A carboxymethyl cellulase gene, cel5B, was cloned, sequenced, and expressed in Escherichia coli. pRCS20 in E. coli was identified from metagenomic cosmid library of cow rumen for cellulase activity on a carboxymethyl cellulose agar plates. Cosmid clone (RCS20) was partially digested with Sau3AI, ligated into BamHI site of pBluescript II SK+ vector, and transformed into E. coli DH5α. The insert DNA of 1.3 kb was obtained, designated cel5B, which has the activity of hydrolyzation of CMC. The cel5B gene had an open reading frame (ORF) of 1,059 bp encoding 352 amino acids with a signal peptide of 48 amino acids and the conserved region, VIYEIYNEPL, belongs to the glycosyl hydrolase family 5. The molecular mass of Cel5B protein expressed from E. coli DH5α exhibited to be about 34 kDa by CMC-SDS-PAGE. The optimal pH was 8.0, and the optimal temperature was about 50℃ for its enzymatic activity.

• Tae-Ho Kang(Division of Applied Life Science (BK21 Program), Gyeongsang National Univ.)
• Min-Keun Kim(Gyeongsangnam-do Agricultural Research and Extension Service)
• Dhirendra Nath Barman(Division of Applied Life Science (BK21 Program), Gyeongsang National Univ.)
• Jung-Ho Kim(Department of Agricultural Chemistry, Sunchon National University)
• Hoon Kim(Department of Agricultural Chemistry, Sunchon National University)
• Han-Dae Yun(Division of Applied Life Science (BK21 Program), Gyeongsang National Univ., Research Institute of Agriculture and Life Science, Gyeongsang National Univ.) Corresponding author