Agarose-gel-immobilized recombinant bacterial biosensors for simple and disposable on-site detection of phenolic compounds

In this study, recombinant bacterial biosensors were immobilized in an agarose matrix and used for the simple and disposable field monitoring of phenolic compounds. In brief, Escherichia coli cells harboring the pLZCapR plasmid, which was previously designed to express the beta-galactosidase reporter gene in the presence of phenolic compounds, were immobilized in agarose gel with or without a substrate [chlorophenol red beta-galactopyranoside (CPRG)] and dispensed to the wells of a 96-well plate. Analytes were added to the wells, and color development was monitored either directly from wells containing intact cells co-immobilized with CPRG (SYS I), or using cells that were lysed prior to the addition of CPRG (SYS L). SYS L showed relatively higher intensities and faster color development than SYS I. However, both systems developed a red color (representing hydrolysis of CPRG) in the presence of 10 mu M to 10 similar to 100 mM phenol, with maximum responses seen at 1 similar to 5 and 50 mM phenol for SYS I and SYS L, respectively. Other phenolic compounds (2-chlorophenol, 2-methylphenol, 3-methylphenol, 4-chlorophenol, 2-nitrophenol, resorcinol, catechol, and 2,5-dimethylphenol) were also detected by the systems, with varied detection ranges and responses. The agarose-immobilized biosensors were stable for 28 days, retaining 39 similar to 69% of their activities when stored at 4A degrees C without nutrients or additives. The immobilized biosensors described herein do not require the on-site addition of a substrate (in the case of SYS I), the pretreatment of samples, or the use of unwieldy instruments for the on-site monitoring of phenolic compounds from environmental samples.