Determination of some safety characteristics of foodborne lactic acid bacteria

A total of 87, previously described for their technological properties and identified by 16S rRNA sequence analysis, lactic acid bacteria (LAB) isolated from cheese and yogurt were used in this study to determine the safety characteristics of LAB. The results showed that 48 LAB tested had gelatinase activity and 19 LAB had biofilm formation capability. 22 LAB strains (16 L. fermentum, 3 L. bulgaricus, 1 L. actis, 1 L. paracasei and 1 L. plantarum) have found to produce all of the biogenic amine tested which were histidine, tyrosine, ornithine, tryptophan, phenylalanine, and lysine decarboxylase enzymes None of the isolates showed hemolytic activity or DNase production. 64 isolates had extracellular protease activity on skim milk agar, whereas 27 and 84 strains showed zone formation on milk agar and casein agar, respectively. In addition, 25 of the 87 strains formed zones on all three media. There was no strain having a zone-negative result for all of the media tested. As a result, a total of 20 LAB out of 87 LAB isolated from different milk and yogurt samples (L. bulgaricus PLa18B, PLa23B, PLc36A, YLa12B, YLa27C, YLa31A, YLj15C (A), YLj22A, and YLr26A (B); L. fermentum PLc27B(A), PLr2B, YLa16C, and YLa37B; L. rhamnosus PLc23B(A), PLc36A(A), PLj6B, and PLj6B1; 1 P. acidilactici PLr8D(A2); 1 L. lactis PLr7A(A); 1 L. plantarum PLj18A1) have found to be negative for hemolytic activity, gelatinase, DNase, and amino acid decarboxylase production, biofilm formation, and extracellular protease activity. These straines are also negative for the genes involved in virulence; hyl, asa1, esp, cylA, efaA, and ace, in amino acid decarboxylase;hdc and tdc,and in antibiotic resistance; ermB, ermC, aac(6ʹ) aph(2ʹʹ), cat, tetK, tetL, tetM, tetS, tetQ, tetX, vanA, vanB, vanC, and vanX. In terms of all these parameters examined, these LAB have been interpreted as reliable. Keywords: LAB, safety, virulence, antibiotic, risk