S160a: Bacterial contamination of fuel ethanol production

Commercial fuel ethanol is not produced under sterile, pure-culture conditions, and consequently bacterial contamination is a recurring problem.  The offending microbes are generally species of lactic acid bacteria that drain the sugar available for conversion to ethanol and scavenge essential micronutrients required for optimal yeast growth.  Acute infections occur unpredictably, and bacterial byproducts such as acetic and lactic acids inhibit yeast growth, which may result in “stuck” fermentations.  Antibiotics are frequently used to control bacterial contamination but extensive use of antibiotics may select for strains with decreased susceptibility to these agents.  Intervention strategies to prevent and control bacterial contamination in fuel ethanol production will be discussed, and alternative technologies to replace antibiotics will be presented.