Short communication: Antimicrobial potential of Lactobacillus plantarum strains isolated from Slovak raw sheep milk cheeses

Abstract

The objective of this study was to screen Lactobacillus plantarum strains isolated from the traditional Slovak raw sheep milk cheese for their inhibitory potential. Seventy-two strains were obtained from samples of raw sheep milk and raw sheep milk cheeses collected from April 2017 to September 2018, in 23 geographical areas of Eastern Slovakia, by inoculation of de Man, Rogosa, and Sharpe agar plates (Oxoid, Basingstoke, UK). Using both the genus-and species-specific PCR methods, 43 strains were identified as Lactobacillus spp., and 10 strains were confirmed as Lb. plantarum. First, the whole bacterial cultures of Lb. plantarum strains were tested by disc diffusion assay. All showed very good antibacterial activities against 6 selected foodborne pathogens, including Escherichia coli, Salmonella Enteritidis, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus. Then, cell-free neutralized supernatants and partially purified bacteriocins were prepared from the 4 Lb. plantarum strains that exhibited the best antibacterial potential, and they were tested the same way as the whole bacterial cultures. Seven of the 10 Lb. plantarum strains harbored the plnEF gene, 3 strains harbored the plnD gene, and 2 strains possessed both the plnA and plnC genes that encode the production of the respective plantaricins. The presence of both plnR and plnL genes was only detected in a single Lb. plantarum isolate. Based on the results of this study, 4 strains of Lb. plantarum appeared to be suitable candidates for further testing in the dairy manufacturing sector, particularly in the production of raw sheep milk products.

Comparison of the Probiotic Potential between Lactiplantibacillus plantarum Isolated from Kimchi and Standard Probiotic Strains Isolated from Different Sources

“…Lpb. plantarum strains are known to produce a wide range of antibacterial compounds, including bacteriocins, organic acids, ethanol, diacetyl, and H 2 O 2 [ 28 , 29 , 30 ]. Furthermore, antibacterial substances produced by LAB are generally recognized as non-toxic and non-irritant components because they are naturally degraded in the body or the environment [ 31 , 32 ].…”

Antimicrobial Resistance of Lactobacillus johnsonii and Lactobacillus zeae in Raw Milk

“…The presence of lactobacilli in raw milk has been confirmed by several studies, including Vataščinová et al, where in 23 geographical areas of Eastern Slovakia, 43 strains have been identified as Lactobacillus sp. [31]. However, the high nutrient content of raw milk during storage makes it a suitable medium for a large number of other microorganisms, such as C. perfringens, S. aureus, E. coli, L. monocytogenes, Salmonella spp., Bacillus cereus, Streptococcus sp., etc., which develop rapidly in it and cause its deterioration [32].…”

Microbiome Associated with Slovak Traditional Ewe’s Milk Lump Cheese

“…In Slovakia, dairy products made from ewe's milk include, e.g., traditional cheeses such as "parenica", "korbáčik" "oštiepok", and Liptauer bryndza, and also ewe's milk lump cheese, either fresh or smoked [3][4][5]. "Parenica", "korbáčik" "oštiepok" and Liptauer bryndza, as well as Oravian korbáčik cheese and Zázrivá korbáčik cheese, were designed to be PGI products, meaning products with protected geographical indication [6,7].…”

“…These various microbiota can play vital roles in the development of the organoleptic properties of cheese, nutrient composition, shelf-life, and safety [8]. The bacterial population in those cheeses has been already studied [2,5] using the standard microbiological method.…”