An investigation on probiotic properties and safety evaluation of non-starter lactic acid bacteria from traditional Turkish yoghurt

Yoghurt, produced by Lactobacillus delbrueckii subsp. bulgaricus and

Streptococcus thermophilus, is one of important fermented products

worldwide. This product is produced industrially on a large-scale, but it is

still produced using traditional methods in many countries. Non-starter lactic acid bacteria other than

the yoghurt bacteria may be present in traditional yoghurts due to the insufficient aseptic conditions

in the homemade production. Therefore, it is quite important to determine beneficial and/or harmful

effects on health of the non-starter lactic acid bacteria in yoghurt. The aim of this study was to

investigate probiotic (tolerance to simulated gastric juice and bile salts, antimicrobial activity, auto/co

aggregation, hydrophobicity, bile salt hydrolase activity, in vitro cholesterol lowering potential) and

safety properties (antibiotic resistant profile, presence of virulence genes, etc.) of non-starter lactic

acid bacteria from traditional yoghurt samples, including Enterococcus faecium YH36, Lactococcus

lactis YH56, Limosilactobacillus fermentum YH35, YH42, and YH43. All isolates tolerated to simulated

gastric juice by 37.88-91.53%, while to 0.3, 0.5, and 1% bile salts by 0.54-64.48%. E. faecium YH36, L.

fermentum YH35, YH42, and YH43 strains inhibited two or more pathogens including E. coli O157:H7,

S. aureus ATCC 29213, P. aeruginosa ATCC 9027, S. Typhimurium RSHMB 95091. All strains had auto

aggregation (3.96-22.04%) and hydrophobicity ability (7.33-64.82%). Moreover, the isolates

aggregated with E. coli O157:H7, S. aureus ATCC 29213, S. Typhimurium RSHMB 95091, and L.

monocytogenes ATCC 7644 by 5.53-22.28%. E. faecium YH36 and L. lactis YH56 lowered cholesterol

level by 71.57-4.14%, respectively. All isolates were sensitive to ampicillin, erythromycin, clindamycin

(except E. faecium YH36), tetracycline, chloramphenicol, while resistant to vancomycin (except E.

faecium YH36 and L. lactis YH56), gentamicin (except L. lactis YH56), kanamycin (except L. lactis YH56),

and streptomycin (except L. lactis YH56). In addition, gelE and efaAfs virulence genes were detected in

L. lactis YH56 and L. fermentum YH42, respectively. These results showed that there could present

potential probiotic non-starter lactic acid bacteria with some virulence genes in traditional yoghurts.

Finally, it was revealed that not only yoghurt bacteria but also non-starter lactic acid bacteria should

be investigated in terms of food safety and human health.