Hydrogen-producing Escherichia coli strains overexpressing lactose permease: FT-IR analysis of the lactose-induced stress

Biotechnol Appl Biochem. 2014 Mar-Apr;61(2):111-7. doi: 10.1002/bab.1128. Epub 2014 Feb 26.

Abstract

The lactose permease gene (lacY) was overexpressed in the septuple knockout mutant of Escherichia coli, previously engineered for hydrogen production from glucose. It was expected that raising the lactose transporter activity would elevate the intracellular lactose concentration, inactivate the lactose repressor, induce the lactose operon, and as a result stimulate overall lactose consumption and conversion. However, overexpression of the lactose transporter caused a considerable growth delay in the recombinant strain on lactose, resembling to some extent the "lactose killing" phenomenon. Therefore, the recombinant strain was subjected to selection on lactose-containing media. Selection on plates with 3% lactose yielded a strain with a decreased content of the recombinant plasmid but with an improved ability to grow and produce hydrogen on lactose. Macromolecular analysis of its biomass by means of Fourier transform-infrared spectroscopy demonstrated that increase of the cellular polysaccharide content might contribute to the adaptation of E. coli to lactose stress.

Keywords: Escherichia coli; FT-IR spectroscopy; biohydrogen fermentation; glycogen; lactose; lactose permease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Escherichia coli / enzymology
  • Gene Expression Regulation, Bacterial
  • Hydrogen / chemistry
  • Hydrogen / metabolism
  • Lactose / metabolism*
  • Membrane Transport Proteins / biosynthesis*
  • Membrane Transport Proteins / genetics
  • Polysaccharides, Bacterial / biosynthesis*
  • Spectroscopy, Fourier Transform Infrared
  • Stress, Physiological / genetics*

Substances

  • Membrane Transport Proteins
  • Polysaccharides, Bacterial
  • Hydrogen
  • lactose permease
  • Lactose