ARS | Publication request: Impact of using virginiamycin in the fuel ethanol production process on distillers grains coproducts

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 16, 2012
Publication Date: August 16, 2012
Citation: Bischoff, K.M., Edrington, T.S., Rich, J.O., Zhang, Y. 2012. Impact of using virginiamycin in the fuel ethanol production process on distillers grains coproducts [abstract]. Society for Industrial Microbiology and Biotechnology. S123.

Technical Abstract: Antibiotics are frequently used to reduce bacterial contamination in commercial fuel ethanol fermentations, but there is concern that antibiotic residues may persist in the distillers grains (DDG) coproducts that are utilized for cattle feed. A study was conducted in the pilot plant facilities at the National Corn to Ethanol Research Center, Edwardsville, IL, to trace the antibiotic virginiamycin through the ethanol production process, and to evaluate the impact of feeding the resultant DDGs on antibiotic sensitivity of commensal bacteria in cattle. Three 3,500 gallon fermentor runs were performed: one with no antibiotic (F1), one dosed with 2 ppm of a commercial virginiamycin product (F2), and one dosed at 20 ppm of virginiamycin product (F3). Using LC/MS, virginiamycin M was detected in extracts of all process intermediates (beer, whole stillage, thin stillage, syrup, wet-cake, and DDGS) from the F3 run. Furthermore, antibiotic activity was detected by bioassay in DDGS from both the F2 and F3 runs, with values of 0.7 ppm and 8.9 ppm virginiamycin, respectively. The DDGs were incorporated into four feedlot rations containing 8% of each respective DDG batch, or 8% of the F1 DDG + 22.5 g/ton V-Max50™ (virginiamycin, positive control). Fecal samples were collected from crossbred beef steers fed these rations, and cultured for Escherichia coli and Enterococcus. No changes (P > 0.05) due to treatment were observed in susceptibilities to 15 antimicrobials for the E. coli isolates. The Enterococcus isolates were resistant to more antibiotics, although this was related to the species of Enterococcus rather than the treatment. In general, treatment had little effect on prevalence of resistance genes in Enterococcus isolates, the exception being the ermB gene which was higher in the control and 2 ppm treatments on some of the collection days. Although biologically active antibiotic may persist in distillers grains produced from fermentations treated with virginiamycin, it appears that feeding these DDGs should have minimal impact on dissemination of antibiotic resistance among enteric bacteria.