A new beta-mannosidase gene, designated as man2S27, was cloned from Streptomyces sp. S27 using the colony PCR method and expressed in Escherichia coil BL21 (DE3). The full-length gene consists of 2499 bp and encodes 832 amino acids with a calculated molecular mass of 92.6 kDa. The amino acid sequence shares highest identity of 62.6% with the mannosidase Man2A from Cellulomonas fimi which belongs to the glycoside hydrolase family 2. Purified recombinant Man2S27 showed optimal activity at pH 7.0 and 50 degrees C. The specific activity, K-m and k(cat) values for p-nitrophenyl-beta-D-mannopyranoside (p-NP-beta-MP) were 35.3 U mg(-1), 0.23 mM. and 305 s(-1), respectively. Low transglycosylation activity was observed when Man2S27 was incubated with p-NP-beta-MP (glycosyl donor) and methyl-alpha-D-mannopyranoside (p-NP-alpha-MP) (acceptor) at 50 degrees C and pH 7.0, and a small amount of methylmannobioside was synthesized. Using locust bean gum as the substrate, more reducing sugars were liberated by the synergistic action of Man2S27 and beta-mannanase (Man5S27), and the synergy degree in sequential reactions with Man5S27 firstly and Man2S27 secondly was higher than that in the simultaneous reactions. (C) 2011 Elsevier Inc. All rights reserved.