Technological and safety assessment of selected lactic acid bacteria for cheese starter cultures design: Enzymatic and antimicrobial activity, antibiotic resistance and biogenic amine production

Twenty lactic acid bacteria (LAB) isolated from artisanal cheeses and previously selected for their technological properties were screened for their enzymatic activities, antimicrobial activity and safety. The aim was to select those LAB strains that were safe and showed advantageous properties for the development of starter cultures for cheese making, discarding those that could transfer antibiotic resistance or produce any toxic biogenic amines. Aminopeptidase activities were detected in most strains, particularly high for the substrate leucine arylamidase, and most lactobacilli and Leuconostoc strains showed high beta-galactosidase activity. Glutamate dehydrogenase (GDH) activity was detected in 13 strains, although the activity values varied widely. All strains showed anti-microbial activity against the indicator microorganisms due to acid production. However, only one of the Lactiplantibacillus plantarum strains showed an inhibitory activity against Enterococcus faecalis due to bacteriocin-like compounds. In particular, Levilactobacillus brevis TAUL1567 and Lactiplantibacillus paraplantarum TAUL1399 showed resistance to tetracycline and ampicillin, respectively, above the cut-off values and were therefore excluded. Tyramine was only produced by L. brevis TAUL1567 (193.15 mu g ml(-1)), while putrescine was produced by this strain and two strains of Lactococcus lactis. Finally, 14 strains produced gamma-aminobutyric acid (GABA), five of them at concentrations around or above 100 mu g ml(-1).

Automated summary

In this study, 20 lactic acid bacteria (LAB) strains were isolated from artisanal cheeses and evaluated for their enzymatic activities, antimicrobial activity, and safety. Most strains exhibited aminopeptidase and beta-galactosidase activities. Glutamate dehydrogenase (GDH) activity was detected in 13 strains. All strains showed antimicrobial activity and one strain showed inhibitory activity against Enterococcus faecalis. Some strains exhibited resistance to antibiotics and produced biogenic amines. Additionally, several strains produced gamma-aminobutyric acid (GABA) at high concentrations.