Aims: To select lactic acid bacteria with potential silage inoculant properties.
The bio-control activity against mycotoxicogenic fungi and the presence of
antibiotics resistance gene were also evaluated.
Methods and Results: Lactobacillus rhamnosus RC007 and Lactobacillus
plantarum RC009 were selected on the basis of growth rate and efficacy in
reducing the pH of maize extract medium; therefore, they were evaluated for
their bio-control ability against Fusarium graminearum and Aspergillus
parasiticus. Studies on lag phase, growth rate and aflatoxin B1 (AFB1) and
zearalenone (ZEA) production were carried out in vitro under different regimes
of aw (095 and 099); pH (4 and 6); temperature (25 and 37°C); and oxygen
availability (normal and reduced). Lactobacillus rhamnosus RC007 was able to
completely inhibit the F. graminearum growth at all assayed conditions, while
Lact. plantarum RC009 only did it at pH 4. Both Lactobacillus strains were able
to significantly reduce the A. parasiticus growth rate mainly at 099 aw. A
decrease in ZEA production was observed as result of Lactobacillus strains –
F. graminearum interaction; however, the A. parasiticus- Lact. plantarum
interaction resulted in an increased AFB1 production. Lactobacillus rhamnosus
RC007 proved to have no genes for resistance to the tested antibiotics.
Conclusions: The ability of Lact. rhamnosus RC007 to rapidly drop the pH
and to inhibit fungal growth and mycotoxin production and the absence of
antibiotic resistance genes shows the potential of its application as inoculant
and bio-control agent in animal feed.
Significance and Impact of the Study: This study demonstrated the
importance of selecting bacteria for silage inoculants not only for the
improvement of silage fermentation but also for their effects on
mycotoxicogenic fungi and the resulting mycotoxin production due to the risk
that they may involve.