Probiotic properties of Enterococcus faecium EF9296 strain isolated from silage

Abstract

Ensilage means preserving forage fed by livestock when fresh material is less available. When the silo is opened, the silage is exposed to air and this leads to aerobic deterioration whereby aerobic microorganisms degrade lactic acid. Therefore, it is necessary to use some additives to control microbes in silage fermentation. The strain EF9296, isolate from silage was allotted to the species Enterococcus faecium by genotyping. This strain is sensitive to ampicillin (10 μg), erythromycin (15 μg), tetracycline, rifampicin, vancomycin (30 μg) and it is kanamycin-resistant (30 μg). EF9296 strain possess good adhesive capability to human as well as to canine mucus (human 5.5 log 10 cfu/ml, canine 4.7 log 10 cfu/ml). In addition, EF9296 is bile tolerant, lactic acid producing (0.997 ± 0.29 mmol/l) with ureolytic activity (16.9 ± 1.2 nkat/ml). The strain EF9296 produces a bacteriocin-like substance with the inhibitory activity against Gram-positive bacteria including enterococci and L. monocytogenes with activity from 100 to 800 AU/ml. Amplified fragment of bacteriocin produced by 9296 strain corresponds with PCR signal for a structural gene of well-known enterocin A. Ent. faecium 9296 strain reached the stationary phase at 8 h in Trypticase-soy broth (11.57 ± 0.07 log 10 cfu/ml) and at 10 h in rumen fluid (9.25 ± 0.48 log 10 cfu/ml). It means, EF9296 strain grew in both media, although its growth in rumen fluid was slower in comparison with counts in TSY broth. In addition, the antilisterial effect of Enterococcus faecium EF9296 in rumen fluid was detected in experimental sample after 6 h from EF9296 strain application in comparison to the Listeria control sample (0.4 log). This effect was prolonged up to the end of the experiment (8 h - 0.44 log, 10 h - 0.65 log, 12 h - 0.62 log). Enterococcus faecium EF9296 strain might be used as potential probiotic to protect silage against microbial contaminants e.g. Listeria spp.