Antimicrobial properties of Pediococcus acidilactici and Pediococcus pentosaceus isolated from silage

Abstract

Aims:The objective of this study was to isolate multifunctional bacteriocin-producing strains; to characterize the expressed bacteriocin for the control of Listeria monocytogenes and vancomycin-resistant Enterococcus; to evaluate the safety of studied strains; and to explore their antifungal activity. Methods and Results: Two Pediococcus strains were isolated from silage samples obtained from an organic farm in Belogradchik, Bulgaria. The strains were identified by 16S rRNA sequencing analysis and characterized as bacteriocins producers. Strong antimicrobial activity was detected against more than 74 different strains of Listeria monocytogenes, 27 different vancomycin-resistant Enterococcus strains. In addition, studied strains were able to inhibit the growth of strains of Alternaria alternate, Aspergillus flavus, Aspergillus niger, Cladosporium sphaerospermum, Penicillium chrysogenum and Penicillium expansum. Some aspects of the antimicrobial mode of action were evaluated, including killing curves and aggregation properties. Both strains generated positive PCR results for the presence of pediocin PA-1, but not for other bacteriocins evaluated in this screening process. Metabolomic analysis of the cell-free supernatants from both strains was performed in order to explain the observed antifungal activity against different moulds. According to PCA and PLS-DA score plot, P. acidilactici ST3522BG and P. pentosaceus ST3633BG were clearly clustered from control (MRS). Increases in the production of benzoic acid, 2-hydroxyisocaproic acid, β-phenyl-lactic acid, α-hydroxybutyric acid and 1,3-butanediol were recorded, these metabolites were previously described as antifungal. Conclusions: Pediococcus acidilactici ST3522BG and P. pentosaceus ST3633BG were evaluated as producing bacteriocin strains with high specificity against Listeria and vancomycin-resistant Enterococcus species. In addition, both investigated Pediococcus strains were evaluated as producer of effective antifungal metabolites with potential for the inhibition of mycotoxin-producing moulds. Significance and Impact of the Study:To the best of our knowledge, this report is a pioneer in the evaluation of Pediococcus strains isolated from silage with highly specific bacteriocinogenic antimicrobial activity against Listeria spp. and vancomycin-resistant Enterococcus spp., and antifungal activity against mycotoxin-producing moulds.

Safety and beneficial properties of bacteriocinogenic Pediococcus acidilactici and Pediococcus pentosaceus isolated from silage

“…Laboratory simulation of clover silage model was prepared, sterilized and artificially contaminated with bacteriocinogenic strains (P. acidilactici ST3522BG and P. pentosaceus ST3633BG) and/or L. monocytogenes ATCC 15313 to prove the hypothesis for bioprotective effect of studied Pedicoccus strains. In our previous work (Fugaban et al 2021), we were not able to detect L. monocytogenes in the silage samples obtained from a local farm, and only one of the tested samples generated positive for L. innocua, observed only after the enrichment procedure. We hypothesized that this can be related to the presence of two different bacteriocinogenic strains in that silage samples, isolated and characterized regarding their strong antimicrobial activity against 74 different L. monocytogenes strains used as test organisms in the evaluation of bacteriocinogenic properties of P. acidilactici ST3522BG and P. pentosaceus ST3633BG (Fugaban et al 2021).…”

“…Moreover, that antimicrobials can be effective against bacterial species, including L. monocytogenes (Fugaban et al 2021), and inhibitory processes in the studied model silage system need to be related to the production of bacteriocins, as their expressions were recorded (Fig. 1), other antimicrobial metabolites, as already described (Fugaban et al 2021) and possible formation of additional antimicrobials as a result of digestion of the plant material during the fermentation process.…”

“…Will be speculative if will try to explain observed inhibition of L. monocytogenes ATCC 15313 only as consequence of effect of produced bacteriocins by P. acidilactici ST3522BG and P. pentosaceus ST3633BG. Both Pediococcus strains were clearly described as able to produce highly effective bacteriocins with strong anti-Listeiria activity (Fugaban et al 2021); however, in the same work, authors evaluated the production by metabolomic analysis of arsenal of other antimicrobial metabolites and pointed their role in the inhibitory process mainly against different moulds. Moreover, that antimicrobials can be effective against bacterial species, including L. monocytogenes (Fugaban et al 2021), and inhibitory processes in the studied model silage system need to be related to the production of bacteriocins, as their expressions were recorded (Fig.…”

“…Both Pediococcus strains were clearly described as able to produce highly effective bacteriocins with strong anti-Listeiria activity (Fugaban et al 2021); however, in the same work, authors evaluated the production by metabolomic analysis of arsenal of other antimicrobial metabolites and pointed their role in the inhibitory process mainly against different moulds. Moreover, that antimicrobials can be effective against bacterial species, including L. monocytogenes (Fugaban et al 2021), and inhibitory processes in the studied model silage system need to be related to the production of bacteriocins, as their expressions were recorded (Fig. 1), other antimicrobial metabolites, as already described (Fugaban et al 2021) and possible formation of additional antimicrobials as a result of digestion of the plant material during the fermentation process.…”

“…Previous researches (Balgir et al 2013;Bhagat et al 2020) were reported on the safety of different potential beneficial pediococcal cultures. The aim of this study was to evaluate safety and some beneficial features of two previously evaluated as bacteriocinogenic Pediococcus strains (Fugaban et al 2021) and to explore their efficacity to control Listeria monocytogenes in a laboratory prepared clover silage model.…”