The coding region of nprC10 gene corresponding to mature neutral protease (NPRC10) from Bacillus subtilis C10 was heterologously expressed in Escherichia coli BL21 (DE3) by using pET200/D-TOPO expression system. In this work, the effect of some factors such as cell density (OD600) before induction, inducer (IPTG) concentration, induction time, incubation temperature after induction, soluble starch and Ca2+ ion concentrations on extracellular NPRC10 expression and stability were investigated. Our results showed that the crude enzyme exhibited a maximum specific activity of 331.97 unit/mg protein after induction by 0.1 mM IPTG for 19 h at 20oC, an OD600 of 2, a soluble starch concentration of 1.5%, and a Ca2+ ion concentration of 10 mM. NPRC10 belongs to metalloprotease family and it also displays a non-specific hydrolytic acitivity for starch. The enzyme has optimal temperature and pH for activity at around 55oC and 6.5, respectively.
