title: Modeling bacterial contamination of fuel ethanol fermentation.
abstract: The emergence of antibiotic-resistant bacteria may limit the effectiveness of antibiotics to treat bacterial contamination in fuel ethanol plants, and therefore, new antibacterial intervention methods and tools to test their application are needed. Using shake-flask cultures of Saccharomyces cerevisiae grown on saccharified corn mash and strains of lactic acid bacteria isolated from a dry-grind ethanol facility, a simple model to simulate bacterial contamination and infection was developed. Challenging the model with 10(8) CFU/mL Lactobacillus fermentum decreased ethanol yield by 27% and increased residual glucose from 6.2 to 45.5 g/L. The magnitude of the effect was proportional to the initial bacterial load, with 10(5) CFU/mL L. fermentum still producing an 8% decrease in ethanol and a 3.2-fold increase in residual glucose. Infection was also dependent on the bacterial species used to challenge the fermentation, as neither L. delbrueckii ATCC 4797 nor L. amylovorus 0315-7B produced a significant decrease in ethanol when inoculated at a density of 10(8) CFU/mL. In the shake-flask model, treatment with 2 microg/mL virginiamycin mitigated the infection when challenged with a susceptible strain of L. fermentum (MIC for virginiamycin < or =2 ppm), but treatment was ineffective at treating infection by a resistant strain of L. fermentum (MIC = 16 ppm). The model may find application in developing new antibacterial agents and management practices for use in controlling contamination in the fuel ethanol industry.
authors.affiliation: National Center for Agricultural Utilization Research, U.S. Department of Agriculture, Agricultural Research Service, 1815 N. University St., Peoria, Illinois 61604, USA. kenneth.bischoff@ars.usda.gov
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Bischoff
authors.forename: Siqing
authors.initials: S
authors.lastname: Liu
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Leathers
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Worthington
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Rich
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D019149:Bioreactors / Q000382:microbiology*; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D007218:Industrial Microbiology; D007779:Lactobacillus acidophilus / Q000254:growth & development; D048668:Lactobacillus delbrueckii / Q000254:growth & development; D052197:Limosilactobacillus fermentum / Q000187:drug effects / Q000254:growth & development*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D014769:Virginiamycin / Q000494:pharmacology; D003313:Zea mays / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D014769:Virginiamycin; D000431:Ethanol