Immobilization of Recombinant Bacterial Biosensors: a Simple Approach for the On-Site Detection of Phenolic Compounds

Abstract

We herein report the development of an agarose-gel-immobilized recombinant bacterial biosensor simple system for the field monitoring of phenolic compounds. Escherichia coli cells harboring the pLZCapR plasmid, which was previously designed to express the β-galactosidase reporter gene in the presence of phenolic compounds, were co-immobilized with a substrate [chlorophenol red β-galactopyranoside (CPRG) in agarose gel, and dispensed to the wells of a 96-well plate. Field samples were added to the wells and color development was monitored. In the presence of 5 μM to 10 mM of phenol, the biosensor developed a red (representing hydrolysis of CPRG) color. Other phenolic compounds were also detected by this immobilized system, with the pattern resembling that previously reported for the corresponding non-immobilized biosensor. The immobilized cells showed optimum activity when the gel was simultaneously supplemented with 6% dimethyl formamide (DMF), 0.1% SDS and 10 mM CaCl2. The immobilized biosensor described herein does not require the addition of a substrate or the use of unwieldy instruments or sample pretreatments that could complicate field studies.