Boron doped diamond biosensor for detection of Escherichia coli.

o-Nitrophenol, released from o-nitrophenyl-beta-D-galactopyranose as catalyzed by beta-galactosidase, a tetramer of Escherichia coli, has been exploited for the detection of E. coli contamination in foodstuffs. This reaction was detected using a boron doped diamond electrode poised at +0.93 V, without any surface modification. The enzyme was effectively induced by isopropyl-beta-D-thiogalacto-pyranoside with the maximum enzyme activity observed with sodium dodecyl sulfate at 50 degrees C. A biphasic calibration plot was observed: 4 x 10(4) to 2 x 10(5) cells/mL and 2 x 10(5) to 6 x 10(6) cells/mL for the first and second region, respectively. The detection limit was 4 x 10(4) cells/mL with a total analysis time of <1.5 h. Electrode fouling was easily overcome by approximately 40 rapid CV scans, and the method was applicable for detecting E. coli in artificially spiked samples of beef, pork, chicken, milk, and tap water.