Antibiotic residues in dried distillers grains and other fermentation by-products
By John Reuther, Eurofins Central Analytical Laboratories, United States
The worldwide production of ethanol as a gasoline additive is growing rapidly. Commercial fermentation processes such as those involved in ethanol production often have by-products that are used in the food and feed industry. Ethanol plants use only the starch from the corn, and sugar from the sugar cane in the process. The remaining nutrients - protein, fat and fiber as well as residual yeast - are by-products which are currently used to create livestock feed such as Dried Distillers Grains with Solubles (DDGS) and “Brewer’s Yeast” amongst others. Conservative estimates by the Food and Agricultural Policy Research Institute at Iowa State University in Ames indicate that the U.S. ethanol industry is projected to produce 43 million metric tons of DDGS during the 2013-14 market year, based on projected ethanol production of 16.8 billion gallons (63.6 billion liters), satisfying both US and global feed markets.
Regulatory Status
The use of antibiotics is helpful to limit harmful bacterial growth during the early part of the fermentation process. In the US, FDA’s Center for Veterinary Medicine (CVM) is responsible for governing the use of antibiotics in agriculture. For several years manufacturers of fermentation-based ethanol and candidate antibiotics have brought food additive petitions and Generally Recognized as Safe (GRAS) petitions to CVM to allow use of specific antibiotics in the DDGS process, including the use of virginiamycin, erythromycin, Penicillin G, and ampicillin. To date none of these have been approved, and thus CVM has no policy (and no MRL) with regard to residues of any antibiotics in fermentation by-products. A similar situation exists in Europe.
CVM scientists have developed screening methods based on liquid chromatography coupled with mass-spectrometry (LC/MS-MS) for the determination of residues of antibiotics and have monitored these levels for several years. Most notable is the LIC 4438 method which allows sensitive determination of 13 antibiotics. Eurofins Central Analytical Laboratories in the US and Eurofins WEJ Analytik in Germany have adapted this method and provide ethanol plants and the by-product trade with the tools needed for compliance monitoring, and support of regulatory petitions.
Contact: JohnReuther@eurofinsus.com