Formic acid is an effective acidulant, but it can also inhibit microbial decarboxylases and enzymes such as catalases. Overall, the antimicrobial activity of formic acid is primarily against yeasts and some bacteria, whereas lactic acid bacteria and moulds are relatively resistant to its effects (Lueck, 1980). Formic acid is effective in small concentrations (21.7mM) against E. coli. In addition, formic acid treatment can effectively eliminate salmonella from contaminated feeds (Frank, 1994).