A method of controlling undesirable microorganism concentration in an aqueous fluid solution employed in a fermentation process is disclosed. An example of the method includes introducing a fermentable carbohydrate to the aqueous fluid solution. The example method also includes introducing at least one desirable microorganism that is capable of fermenting carbohydrate to the aqueous fluid solution. The example method also includes introducing at least one lauric arginate (LAE) compound as a preservative into the aqueous fluid solution at a rate of between about two (2) pounds and about fifty (50) pounds LAE per ton of distillers grain. The example method also includes adding a surfactant (e.g., Polysorbate 80) to the LAE to improve solubility and efficacy of LAE during the fermentation process.
