| Résumé | ο-Nitrophenol, released from ο-nitrophenyl-β-D-galactopyranose as catalyzed by β-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-β-D-thiogalacto-pyranoside with the maximum enzyme activity observed with sodium dodecyl sulfate at 50 °C. A biphasic calibration plot was observed: 4 × 10⁴ to 2 × 10⁵ cells/mL and 2 × 10⁵ to 6 × 10⁶ cells/mL for the first and second region, respectively. The detection limit was 4 × 10⁴ cells/mL with a total analysis time of <1.5 h. Electrode fouling was easily overcome by ∼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. |
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