Expression of a β-Mannosidase from Paenibacillus polymyxa A-8 in Escherichia coli and Characterization of the Recombinant Enzyme

Paenibacillus polymyxa A-8, which secretes β-mannosidase, was isolated from the soil sample under a pine tree located in the “Laoban” mountain region of Sichuan, China. The β-mannosidase gene (MANB) was isolated from P. polymyxa A-8, using primers according to the complete genome. The MANB (2,550 bp) encoding 849 amino acid residues was expressed in Escherichia coli. The specific activities of β-mannosidase produced by P. polymyxa A-8 and E. coli pET30a-MANB were 12 nkat/mg and 635 nkat/mg respectively. SDS-PAGE analysis indicated that the molecular mass of the recombinant MANB was approximately 96 kDa. The recombinant MANB was active between pH 7.0–8.5 with the maximum activity at pH 7.0. It had good pH stability and adaptability. The MANB had the optimal temperature of 35°C and was relatively stable at 35–40°C. In addition, the MANB activity was enhanced by K(+), Ca(2+), Mn(2+), and Mg(2+) and inhibited by Zn(2+), Cu(2+), and Hg(2+).