Optimization of the whole-cell catalytic activity of recombinant Escherichia coli cells with surface-immobilized organophosphorus hydrolase.

ABSTRACT

Previous studies have verified the feasibility of using Escherichia coli systems that display organophosphorous hydrolase (OPH) on the cell surface as whole-cell catalysts. However, the inefficient display of the enzyme on cell surfaces remains unaddressed. In the present study, multiple optimization experiments on full-length and truncated ice nucleation protein anchors, E. coli host cells, culture media, and culture conditions were performed to optimize whole-cell OPH enzymatic activity. The results show that apart from the dramatic effect of isopropyl-b-d-thiogalactoside concentration and culture temperature, the coordination between the anchor protein, culture media, and host cells is essential for highly efficient OPH display. Under optimal conditions, namely, culturing in M9 medium, 20 °C induction temperature, 0.1 mmol l-1 IPTG, and 100 μmol l-1 Co2+, the engineered E. coli strain MB109-406 that expresses the fusion enzyme InaK-N-OPH exhibited a whole-cell OPH activity of 0.62 U mg-1 ?cell d.wt. This result is much higher than that of several currently available OPH-displaying systems, which shows the potential of the current system for further large-scale industrial or environmental applications.