Voltammetric measurement of Escherichia coli concentration through p-APG hydrolysis by endogenous β-galactosidase

Yu Jui Fan, Yu Chen Hsu, Bing Chen Gu, Chia Che Wu

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This paper reports a facile electrochemical detection method for Escherichia coli (E. coli) that does not use DNA amplification or immunoassay. The detection principle is based on the activity of the β-galactosidase (β-gal) endogenous enzyme, which hydrolyzes p-aminophenyl-β-D-galactopyranoside (p-APG) into p-aminophenol. After E. coli consumes p-APG within 30 min, the remaining p-APG is oxidized on a gold electrode using cyclic voltammetry and square wave voltammetry. The β-gal expression level is increased through treatment with a β-gal expression inducer (isopropyl-β-D-thiogalactopyranoside), and the hydrolysis reaction of p-APG is facilitated through permeabilization treatment with sodium dodecyl sulfate. The calibration curve for E. coli has a working range of 102–104 colony-forming units per mL in nutrient broth buffer. The total assay time is less than 100 min. The successful application of this approach indicates the possibility of rapid detection.

Original languageEnglish
Article number104641
JournalMicrochemical Journal
Publication statusPublished - May 2020


ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy

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