Determination of safety status and probiotic properties ofEnterococcusstrains isolated from traditional cheeses in Turkey

Abstract

Aims This study aimed to evaluate the probiotic properties of Enterococcus strains isolated from Turkish traditional cheeses. Methods and results Fifty-two Enterococcus spp. were taxonomically determined as follows: Enterococcus faecium (26), Enterococcus faecalis (18), Enterococcus durans (6), and Enterococcus italicus (2). The ability of isolates/strains to survive the harsh conditions (acidity and in-vitro gastric solution) of the gastrointestinal tract was established. They also showed auto-aggregation, hydrophobicity, and co-aggregation ability. Hydrophobicities of the strains were found between 0.8%–21%, 0.7%–56%, and 2%–63% for xylene, chloroform, and ethyl acetate, respectively. Autoaggregation values of the Enterococcus strains were 4%–20%, 7%–30%, and 36%–98% after 2, 4, and 24-h incubation, respectively. In this study, the Enterococcus strains tested showed co-aggregation ability with the Escherichia coli ATCC 25922, Salmonella Typhimurium ATCC 14028, and Staphylococcus aureus ATCC 25923. The results of PCR amplification revealed that only five strains possess virulence factor genes (gelE,asa1,cyl A,esp). We determined antibiotic resistance, biofilm forming abilities, and hemolytic activity for safety evaluation of strains. Conclusions In this large and comprehensive study, we found that only few of Enterococcus strains have promising probiotic potential, among which E. faecalis ES1 and E. faecium EM1 showed the best probiotic properties (are the most promising probiotic candidates).

Evaluation of the probiotic, technological, safety attributes, and GABA-producing capacity of microorganisms isolated from Iranian milk kefir beverages

“…Therefore probiotics must be hemolysin-free (Kim et al, 2022;Rahmani et al, 2022). None of the isolates showed β-hemolysis after 24 h, which is consistent with the results of Baccouri et al (2019), Kanak et al (2023), Yang et al (2023), andRahmani et al (2022).…”

“…However, the present study demonstrated that the percentage of co-aggregation of all isolates with Gram-positive pathogen (L. monocytogenes) was significantly higher than with Gramnegative pathogen (E. coli). Results of previous studies did not show a relationship between the percentage of co-aggregation and Gram stain of the pathogen (Nami et al, 2019;Pytka et al, 2022;Kanak et al, 2023;Yang et al, 2023). Research evidence has shown that the co-aggregation percentage is dependent only on incubation time, probiotics, and pathogen strain (Kanak et al, 2023).…”

“…Results of previous studies did not show a relationship between the percentage of co-aggregation and Gram stain of the pathogen (Nami et al, 2019;Pytka et al, 2022;Kanak et al, 2023;Yang et al, 2023). Research evidence has shown that the co-aggregation percentage is dependent only on incubation time, probiotics, and pathogen strain (Kanak et al, 2023).…”

“…Multiple studies indicate that the ability of different bacterial isolates to withstand conditions in the gastrointestinal tract is influenced by several factors, including the acidity (pH), bile salt concentration, digestive enzymes (pepsin and pancreatin), incubation duration, and the specific strain of the bacteria ( Leite et al, 2015 ; Baccouri et al, 2019 ; Merchán et al, 2020 ; Rahmani et al, 2022 ; Tan et al, 2022 ; Kanak et al, 2023 ). Our study specifically examined how isolates react to a pH level of 2.5 over a 3-h period, as these conditions closely resemble the average acidity and food retention time in the human stomach.…”

“…On the other hand, co-aggregation is when cells adhere to pathogens, aided by protein compounds on their surfaces. Both mechanisms serve as antimicrobial strategies: auto-aggregation prevents pathogen attachment, while co-aggregation exposes pathogens more effectively to probiotic antimicrobial agents like bacteriocins (Hurtado-Romero et al, 2021;Rahmani et al, 2022;Kanak et al, 2023). As illustrated in Figure 3, all isolates exhibited a significant increase in auto-aggregation over time (p-value < 0.05), reaching 64-73% after 24 h. P. fermentans demonstrated the highest level of auto-aggregation, surpassing even the standard probiotic strain L. casei PTTC 1608, while L. lactis showed the lowest.…”