Enhanced electrochemical measurement of β-galactosidase activity in whole cells by coexpression of lactose permease, LacY

Biotechniques. 2022 Nov;73(5):233-237. doi: 10.2144/btn-2022-0090. Epub 2022 Oct 27.


Whole-cell biosensing links the sensing and computing capabilities of microbes to the generation of a detectable reporter. Whole cells enable dynamic biological computation (filtered noise, amplified signals, logic gating etc.). Enzymatic reporters enable in situ signal amplification. Electrochemical measurements are easily quantified and work in turbid environments. In this work we show how the coexpression of the lactose permease, LacY, dramatically improves electrochemical sensing of β-galactosidase (LacZ) expressed as a reporter in whole cells. The permease facilitates transport of the LacZ substrate, 4-aminophenyl β-d-galactopyranoside, which is converted to redox active p-aminophenol, which, in turn, is detected via cyclic voltammetry or chronocoulometry. We show a greater than fourfold improvement enabled by lacY coexpression in cells engineered to respond to bacterial signal molecules, pyocyanin and quorum-sensing autoinducer-2.

Keywords: Miller assay; electrochemical sensing; synthetic biology; whole-cell β-galactosidase assay.

MeSH terms

  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli Proteins*
  • Galactose
  • Membrane Transport Proteins
  • Monosaccharide Transport Proteins
  • Symporters*
  • beta-Galactosidase / metabolism


  • lactose permease
  • Membrane Transport Proteins
  • beta-Galactosidase
  • Galactose
  • Escherichia coli Proteins
  • LacY protein, E coli
  • Monosaccharide Transport Proteins
  • Symporters