Objective This study aimed to isolate bacteriocin-producing lactic acid bacteria (LAB) from raw meat and traditional Turkish meat products and to evaluate their technological properties and safety for potential use as starter cultures in the meat industry. Methods Presumptive LAB were screened for bacteriocin production using indicator strains, and the proteinaceous nature of the antibacterial compounds was confirmed by proteolytic enzymes. The isolates were identified by 16 S rDNA- and species-specific PCR, and their genetic diversity was assessed by RAPD-PCR. Furthermore, bacteriocin stability, bacteriocin type, technological properties, and safety aspects—including antibiotic susceptibility, resistance and virulence genes, hemolytic and gelatinase activities, and biogenic amine production—were evaluated using phenotypic assays and PCR-based methods. Results A total of eight presumptive bacteriocin-producing LAB strains were isolated, seven from raw meat and one from sucuk, a traditional Turkish fermented sausage. Proteolytic enzyme treatments confirmed the antibacterial substances produced by these strains were bacteriocins. 16 S rDNA sequencing and PCR-based analyses identified five isolates as Enterococcus faecium and three as Enterococcus mundtii. All strains were found genetically distinct by RAPD-PCR. Bacteriocins produced by all strains exhibited broad pH stability and heat resistance. PCR and Tricine-SDS-PAGE analyses indicated that E. faecium strains produce enterocin B, whereas E. mundtii strains produce mundticin KS. The E. faecium strains showed rapid acid production, while the E. mundtii strains exhibited moderate acid production. None of the strains displayed extracellular proteolytic or lipolytic activities; however, all exhibited esterase, esterase lipase, leucine arylamidase, acid phosphatase, and naphthol-AS-BI-phosphohydrolase activities. Additionally, E. faecium strains demonstrated valine arylamidase and cystine arylamidase activities, which were absent in E. mundtii strains. Nitrate reductase activity was observed in E. mundtii but absent in E. faecium. The strains were generally susceptible to clinically important antibiotics. The multiple antibiotic resistance (MAR) index of E. mundtii strains was lower than that of E. faecium, whose MAR index ranged from 0.22 to 0.26, indicating that these strains were multidrug- resistant. Notably, E. faecium B7.2 and B7.3 lacked detectable antibiotic resistance genes. However, tetL, aph(3ʹ)-IIIa, and ant(4ʹ)-Ia genes were detected in 50% of the strains. All strains did not exhibited hemolytic and gelatinase activities. Virulence factors were not detected in E. mundtii B33.1; however, the remaining seven strains carried one or both of the efaAfm and acm genes. Furthermore, E. faecium strains decarboxylated tyrosine, whereas E. mundtii exhibited weak activity. The tdc gene was detected in all strains. Conclusion These findings indicate that E. mundtii B33.1 may be safely used as a starter or adjunct culture in food processing. In contrast, the remaining seven strains may pose potential health risks if applied as live cultures in food production. However, purified bacteriocins derived from these strains could have promising applications in food preservation.

Technological properties and safety evaluation of bacteriocinogenic Enterococcus strains isolated from raw meat and traditional meat products in Türkiye

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2026年4月7日

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Burak Geniş,
Yasin Tuncer

摘要

Objective

This study aimed to isolate bacteriocin-producing lactic acid bacteria (LAB) from raw meat and traditional Turkish meat products and to evaluate their technological properties and safety for potential use as starter cultures in the meat industry.

Methods

Presumptive LAB were screened for bacteriocin production using indicator strains, and the proteinaceous nature of the antibacterial compounds was confirmed by proteolytic enzymes. The isolates were identified by 16 S rDNA- and species-specific PCR, and their genetic diversity was assessed by RAPD-PCR. Furthermore, bacteriocin stability, bacteriocin type, technological properties, and safety aspects—including antibiotic susceptibility, resistance and virulence genes, hemolytic and gelatinase activities, and biogenic amine production—were evaluated using phenotypic assays and PCR-based methods.

Results

A total of eight presumptive bacteriocin-producing LAB strains were isolated, seven from raw meat and one from sucuk, a traditional Turkish fermented sausage. Proteolytic enzyme treatments confirmed the antibacterial substances produced by these strains were bacteriocins. 16 S rDNA sequencing and PCR-based analyses identified five isolates as Enterococcus faecium and three as Enterococcus mundtii. All strains were found genetically distinct by RAPD-PCR. Bacteriocins produced by all strains exhibited broad pH stability and heat resistance. PCR and Tricine-SDS-PAGE analyses indicated that E. faecium strains produce enterocin B, whereas E. mundtii strains produce mundticin KS. The E. faecium strains showed rapid acid production, while the E. mundtii strains exhibited moderate acid production. None of the strains displayed extracellular proteolytic or lipolytic activities; however, all exhibited esterase, esterase lipase, leucine arylamidase, acid phosphatase, and naphthol-AS-BI-phosphohydrolase activities. Additionally, E. faecium strains demonstrated valine arylamidase and cystine arylamidase activities, which were absent in E. mundtii strains. Nitrate reductase activity was observed in E. mundtii but absent in E. faecium. The strains were generally susceptible to clinically important antibiotics. The multiple antibiotic resistance (MAR) index of E. mundtii strains was lower than that of E. faecium, whose MAR index ranged from 0.22 to 0.26, indicating that these strains were multidrug- resistant. Notably, E. faecium B7.2 and B7.3 lacked detectable antibiotic resistance genes. However, tetL, aph(3ʹ)-IIIa, and ant(4ʹ)-Ia genes were detected in 50% of the strains. All strains did not exhibited hemolytic and gelatinase activities. Virulence factors were not detected in E. mundtii B33.1; however, the remaining seven strains carried one or both of the efaA_fm and acm genes. Furthermore, E. faecium strains decarboxylated tyrosine, whereas E. mundtii exhibited weak activity. The tdc gene was detected in all strains.

Conclusion

These findings indicate that E. mundtii B33.1 may be safely used as a starter or adjunct culture in food processing. In contrast, the remaining seven strains may pose potential health risks if applied as live cultures in food production. However, purified bacteriocins derived from these strains could have promising applications in food preservation.