Objective: To develop a novel Escherichia coli cell surface display system by using C-terminally truncated NCgl1221 as the anchoring protein, which greatly enriched or optimized the bacterial displayed systems.
Methods: We amplified the sequence of C-terminally truncated NCgl1221 and beta-amylase, and constructed the fusion expression vector. Then we transformed the recombinant plasmids PET-NA and PET-28a into Rosetta (DE3) pLysS. The fusion protein expression was induced by IPTG and identified by SDS-PAGE and Western blot analysis. The IPTG induced strains were immunostained and investigated by fluorescence microscope and flow cytometry to detect the displayed beta-amylase. Finally, we analyzed the activity of beta-amylase and starch hydrolization in order to determine whether the displayed beta-amylase has the activity or not.
Results: The fusion protein was successfully expressed in E. coli, and the active beta-amylase was displayed on the cell surface by fusing it to the C terminus of the anchor. The recombinant strain displaying beta-amylase can utilize soluble starch in the medium.
Conclusion: A novel E. coli surface display system by using C-terminally truncated NCgl1221 as the anchor motif was successfully developed. The active enzyme with a molecular size of 56 kDa was displayed on E. coli by this system, which provided the basis for the application of the system in whole-cell biocatalyst or biosorbent.