Expression of an endoinulinase from Aspergillus ficuum JNSP5-06 in Escherichia coli and its characterization

In this study, the endoinulinase encoded by the endo I gene from Aspergillus ficuum JNSP5-06 was overexpressed in Escherichia coli and the biochemical characterization of recombinant endoinulinase was investigated. The results showed that the molecular weight of recombinant endoinulinase was estimated to be 60 kDa by SDS-PAGE. The Km and Vmax values with inulin as the substrate were found to be (67.4 ± 4.2) mg/mL and (349.2 ± 13.7) mg/mL min, respectively. The optimum pH and temperature of this enzyme were 5.0 and 60 °C, respectively. Its activity was increased by Zn2+, completely inhibited by Ag+, and Cu2+, and strongly inhibited by Al3+, Fe2+, and Fe3+, whereas K+, Ca2+, Mn2+, Mg2+, and Ni2+ had no significant influence on this recombinant endoinulinase activity. The major products of hydrolysis of inulin by the recombinant endoinulinase were fructo-oligosaccharides with degree of polymerization (DP) from 3 to 4.