Lactoside V™ is intended for use in fuel ethanol fermentations. The active ingredient is virginiamycin, which controls a wide range of fermentation contaminants known to be detrimental to ethanol production. LACTOSIDE V antimicrobial is especially effective in controlling gram-positive bacteria, such as Lactobacillus sp., and inhibits protein synthesis in both actively growing and static bacterial cells. Eliminating or controlling bacterial infection prevents competition for glucose, reduces yeast stress and allows increased alcohol yields. LACTOSIDE V antimicrobial is suitable for both low pH and high temperature fermentations and should be added during the fermentation phase of alcohol production.