Concentrated ethanol-derived switchgrass extractives inhibit plant and foodborne pathogens
Bruce, A., H. B. Korotkin, B. H. Ownley, J. Tao, L. M. Kline, N. Labbe, K. D. Gwinn, D. H. D'Souza, and N. Moustaid-Moussa.  2015.  Phytopathology, 105(Suppl. 4):S4.20, Annual Meeting, American Phytopathological Society. August 1-5, Pasadena, CA.

Abstract:
Conversion efficiency of switchgrass lignocellulose to ethanol for biofuel production is reduced by a non-structural portion of the biomass known as extractives. This fraction inhibits enzymes and microorganisms in the biofuel conversion process and contains high concentrations of phenolic compounds. Our goal is to develop a value-added antimicrobial product from switchgrass extractives. Our specific aim was to test four concentrations (30, 45, 60, 75) of ethanol extracts of switchgrass for inhibition of bacterial pathogens in disk diffusion assays with controls. Agrobacterium tumefaciens, Clavibacter michiganensis subsp. michiganensis, C. m. subsp. nebraskensis, Erwinia amylovora, Pseudomonas syringae pv. tabaci, P. s. pv. tomato, Xanthomonas axonopodis pv. malvacearum, X. perforans, Escherichia coli O157 (isolates O111, O26, O45, Cider, and Jack in the Box) or Salmonella enterica [serovars Enteritidis (SE) and Typhimurium (ST)] were spread onto tryptic soy agar. Sterile filter disks treated with extractives were dried to remove ethanol, rehydrated in water, and placed on bacterial spread plates. All concentrations significantly inhibited plant pathogenic bacteria; Xanthomonas was inhibited most and Agrobacterium was inhibited least. Inhibition of S. enterica and E. coli increased significantly as extractives concentration increased. Serovar ST was inhibited more than SE. E. coli isolates varied in sensitivity; Cider and O45 were most inhibited.