Ethanol Oxidation and Acetaldehyde Production in Vitro by Human Intestinal Strains of Escherichia coli under Aerobic, Microaerobic, and Anaerobic Conditions

Abstract

Background: Many human colonic facultative anaerobic and aerobic bacteria are capable of alcohol dehydrogenase (ADH)-mediated ethanol oxidation. In this bacteriocolonic pathway for ethanol oxidation intracolonic ethanol is first oxidized by bacterial ADHs to acetaldehyde, which is further oxidized by either colonic mucosal or bacterial aldehyde dehydrogenases to acetate. The produced acetaldehyde is a highly toxic and carcinogenic agent. This study was aimed to investigate the ethanol oxidation capability and acetaldehyde formation of Escherichia coli IH 50546 and IH 50817. These intestinal E. coli strains expressed either high (IH 50546) or low (IH 50817) ADH activity. Methods: Strains were cultured for 48 h on agar plates supplemented with ethanol under aerobic, microaerobic (6% O₂), and anaerobic conditions. Results: Under aerobic conditions both E. coli