A new probiotic and bacteriocin-producing strain of Enterococcus faecium EF9296 and its use in grass ensiling

Abstract

A new probiotic, bacteriocin-producing strain of <I>Enterococcus faecium</I> EF9296 (isolate of our laboratory) was used in grass ensiling as an inoculant. The antimicrobial effect as well as the nutritive quality of silage was evaluated along with the aerobic stability test. Grass was ensiled with EF9296 strain (10<sup>9</sup> colony-forming units per gram of fresh material) and the silage without EF9296 was also prepared. The silages were processed in 1-litre plastic bottles. The samples were collected at days 0–1 (start of experiment), 7, 14 and 105 of ensiling to check the microbial status and chemical parameters of silage. At the end of ensiling period (day 105) the silages were subjected to an aerobic stability test for 7 days. The EF9296 strain survived and colonized the silage in sufficient counts (10<sup>9</sup>–10<sup>10</sup> cfu/g). The total counts of enterococci and lactic acid bacteria were increased. In the silage inoculated with EF9296 strain, a reduction in <I>E. coli</I>, enterobacteriae, staphylococci and <I>Bacillus</I>-like bacteria was noted mainly at day 7 and 14 of ensiling. Moreover, the counts of <I>Listeria</I> and moulds were reduced during the aerobic stability test. The silage inoculation resulted in a more rapid drop of pH, higher level of lactic acid and in a decrease in the concentration of acetic and butyric acid. The effect of <I>E. faecium</I> EF9296 on the value of pH was prolonged until the end of the experiment (including the aerobic stability test, below 4.3). During the whole ensiling period an increase in DM content in the experimental silage was detected. The <I>E. faecium </I> EF9296 strain represents a promising silage additive to produce silage of good quality and/or to prevent silage contamination.