What is disclosed is a method of reducing undesirable concentrations of microorganisms without the use of man-made antibiotics, comprising the steps of: introducing a quantity of fermentable carbohydrate; sugar or cellulose to an aqueous system; introducing a quantity of desirable microorganism to the aqueous system; introducing at least one acid into the aqueous system, wherein the at least one acid is selected from the group consisting of hops acid, organic acid, or a combination of hops acid and organic acid; and introducing a compound comprised of Lauryl-L-arginine ethyl ester monohydrochloride (LAE) into the aqueous system. The use of LAE as a preservative of distiller's grains and solubles is also disclosed.
