Determination of Virginiamycin, Erythromycin, and Penicillin in Dried Distillers Grains with Soluble

Introduction

Distillers grain (DG), a major coproduct of dry-grind ethanol processing, quadrupled in production during 2004–2005. It is currently the second largest category of processed feed in the U.S., with an estimated 35 million metric tons (tonnes) produced in 2011. Nearly 25% of U.S. DGs are exported and the primary markets are China, Mexico, and Canada. DG is a valuable product to the livestock industry because it is a rich source of protein, fat, minerals, and vitamins, thus making it an excellent feed supplement for livestock and poultry.^1–4 However, bacterial contamination from lactic acid-producing bacteria—such as Lactibacillus, Lueconostoc, and Weissella—is a concern for ethanol production facilities because bacteria compete with yeast for sugar and micronutrients. Antibiotics such as virginiamycin, penicillin, and erythromycin are commonly used during fermentation to inhibit bacterial growth.⁵