Effect of culture condition on high-level expression of recombinant β-mannanase from Bacillus circulans NT 6.7 in Escherichia coli and application in mannan hydrolysis

Abstract

Expression of β-mannanase from Bacillus circulans NT 6.7 in Escherichia coli BL21(DE3) was increased by optimizing the culture condition. β-mannanase activity of 131 U/mL was obtained using modified M9NG as the cultivation medium. Optimum induction temperature at 37°C gave highest mannanase activity of 731 U/mL. Mannanase activity of 1,309 U/mL was obtained using 10 mM lactose induction. Expression of β-mannanase under this optimum condition increased 18.4-fold, while production cost decreased 5-fold compared with the conventional condition using LB medium and IPTG induction at 18°C. β-mannanase activity increased to 2,114 U/mL under fermentation in a 5-L fermenter with pH controlled at 7. This recombinant enzyme hydrolyzed copra meal and LBG into manno-oligosaccharides as mainly mannotriose and mannotetraose.