Antimicrobial effect of selected lactic acid bacteria against microorganisms with decarboxylase activity

Khatantuul Purevdorj,Iva Březinová,Leona Buňková,Adéla Žalková,Pavel Pleva,Kristýna Maršálková

doi:10.5219/740

Abstract

The main purpose of this study was to evaluate the antimicrobial activity of twenty-one bacteriocinogenic lactic acid bacteria (12 strains of Lactococcus lactis subsp. lactis, 4 strains of Lactobacillus gasseri, 3 strains of Lb. helveticus and 2 strains of Lb. acidophilus, LAB) against 28 Staphylococcus and 33 Enterococcus strains able to produce tyramine, putrescine, 2-phenylethylamine and cadaverine. The antimicrobial activity of cell-free supernatants (CFS) from tested LAB was examined by an agar-well diffusion assay. Nine out of twenty-one strains (33%) showed the inhibitory effect on tested enterococci and staphylococci, namely 9 strains of Lactococcus lactis subsp. lactis. The diameters of inhibition zones ranged between 7 mm and 14 mm. The biggest diameter of 14 mm inhibition was obtained with the CFS's from strains CCDM 670 and CCDM 731 on Enterococcus sp. E16 and E28. The cell-free supernatants from Lactococcus lactis subsp. lactis CCDM 71 and from Lactococcus lactis subsp. lactis CCDM 731 displayed the broadest antibacterial activity (52% inhibition of all tested strains). On the other hand, the cell-free supernatants from the screened Lactobacillus strains did not show any inhibitory effect on the tested Staphylococcus and Enterococcus strains. Nowadays, the great attention is given to the antibacterial substances produced by lactic acid bacteria. With the ability to produce a variety of metabolites displaying inhibitory effect, the LAB have great potential in biopreservation of food.

Highlights

Since ancient time, wild microorganisms naturally present in raw material has been played important role in food preservation (Galvéz et al, 2007)
Nisin is the only bacteriocin of gram-positive bacteria, which is approved by the European Food Safety Authority (EFSA) and the U.S Food and Drug Administration (FDA) for use as a food preservative (EFSA, 2006)
Twenty-one lactic acid bacteria able to produce nisin and bacteriocin like inhibitory substances (BLIS) were screened for their antimicrobial effect on 33 Enterococcus strains with decarboxylase activity

Summary

Introduction

Wild microorganisms naturally present in raw material has been played important role in food preservation (Galvéz et al, 2007). The bacteriocins produced by LAB are cationic amphiphilic molecules containing 20 to 60 amino acid residues (Chen and Hoover, 2003). These bacteriocins are thermostable and retained its activity in a wide range of pH values. Nisin is a low-molecularweight polypeptide (34 amino acids) with a pentacyclic structure containing one lanthionine and four βmethyllanthionine residues (Ross et al, 2002) It is produced by Lactococcus lactis subsp. Lactis, commonly found in milk and dairy products (Favaro et al, 2015) It is non-toxic to humans and food containing nisin, can carry the label "preserved in a natural way" (Cleveland et al, 2001)

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