Surface display provides an efficient expression system for production of recombinant proteins and bacterial whole cell biosensor in E. coli

A novel bacterial display vector based on Escherichia coli has been engineered for recombinant protein production and purification. Accordingly, a construct harboring the enhanced green fluorescent protein (EGFP) and the ice nucleation protein (INP) was designed to produce EGFP via the surface display in E. coli cells. The fusion EGFPexpressed cells were then investigated using fluorescence measurement, SDSand native-PAGE before and after TEV protease digestion. The displayed EGFP was obtained with a recovery of 57.7 % as a single band on SDSPAGE. Next, the efficiency of the cell surface display for mutant EGFP (EGFP S202H/Q204H) was examined in sensing copper ions. Under optimal conditions, a satisfactorily linear range for copper ions concentrations up to 10 nM with a detection limit of 0.073 nM was obtained for cell-displayed mutant EGFP (mEGFP). In the presence of bacterial cell lysates and purified mEGFP, response to copper was linear in the 2-10 nM and 0.1-2 mu M concentration range, respectively, with a 1.3 nM and 0.14 mu M limit of detection. The sensitivity of bacterial cell lysates and surface-displayed mEGFP in the detection of copper ions is higher than the purified mEGFP.