Fructooligosaccharide Utilization by Salmonellae ^† and Potential Direct-Fed-Microbial Bacteria for Poultry

Experiments were done to characterize potential direct-fed-microbial (DFM) bacteria for poultry and Salmonella spp. with respect to their abilities to metabolize fructooligosaccharide substrates (FOS-50^® or pure FOS). Oxygen uptake (QO₂) by these bacteria in media containing either glucose, FOS-50^®, or FOS was determined with a Warburg respirometer. QO₂ values for Salmonella spp. In media containing glucose or FOS-50^® were similar(P >0.05); however, QO₂ values in medium with FOS were significantly lower (P <0.05).The QO₂ values for Enterococcus faecium , Lactococcus lactis , and Pediococcus sp. were considerably lower, reflecting the inability of these bacteria to oxidatively utilize these carbohydrates. The ability of E. faecium , L. lactis , and Pediococcus sp. to ferment glucose, FOS-50^®, or FOS was determined by measuring pH changes of the media. All carbohydrate sources were fermented by these bacteria, but at different rates. The lowest pH values (<4.6) were obtained in inoculated media supplemented with glucose. The highest fermentation rate was achieved by Pediococcus sp. (pH< 5.2 at 7h), while L. lactis showed the slowest fermentation rate (pH > 6.4 at 10 h). To test the ability of Pediococcus sp. to hydrolyze FOS substrates, a cell-free extract was spectrophotometrically analyzed for the presence of active enzymes capable of hydrolyzing FOS or sucrose (a component of FOS). Hydrolysis of FOS (release of glucose) but not of sucrose was evident. However, equal activity was found in aqueous FOS without the cell-free extract, which suggests that free glucose was a component of the FOS solution tested.