Abstract: A method of controlling bacterial contamination by inhibiting bacterial growth in an aqueous fermentation solution employed in a sugar fermentation process is provided. The method includes the steps of: (a) introducing a surfactant composition into the aqueous fermentation solution; (b) introducing an acid into the aqueous fermentation solution in a sufficient quantity to provide a pH value in a range of about 4.5 or less; and (c) mixing the aqueous fermentation solution with yeast, wherein a combination of the surfactant composition and the pH provide antibacterial effects. The synergistic combination of the surfactant composition and the acidic pH of the aqueous fermentation solution are effective to control the levels of one or more of the undesirable bacteria and/or bacterial by-products, while the yeast (e.g., Saccharomyces cerevisiae) that convert sugar to ethanol remain suitably viable.