Antimicrobial Potential of Food Lactic Acid Bacteria: Bioactive Peptide Decrypting from Caseins and Bacteriocin Production

Abstract

Lactic acid bacteria (LAB) potential in the food industry and in the biotechnological sector is a well-established interest. LAB potential in counteracting especially food-borne infections has received growing attention, but despite being a road full of promises is yet poorly explored. Furthermore, the ability of LAB to produce antimicrobial compounds, both by ribosomal synthesis and by decrypting them from proteins, is of high value when considering the growing impact of multidrug resistant strains. The antimicrobial potential of 14 food-derived lactic acid bacteria strains has been investigated in this study. Among them, four strains were able to counteract Listeria monocytogenes growth: Lactococcus lactis SN12 and L. lactis SN17 by high lactic acid production, whereas L. lactis 41FLL3 and Lactobacillus sakei I151 by Nisin Z and Sakacin P production, respectively. Strains Lactococcus lactis MG1363, Lactobacillus rhamnosus 17D10 and Lactobacillus helveticus 4D5 were tested and selected for their potential attitude to hydrolyze caseins. All the strains were able to release bioactive peptides with already known antimicrobial, antihypertensive and opioid activities. These features render these strains or their bioactive molecules suitable for use in food as biocontrol agents, or as nutraceutical supplements to treat mild disorders such as moderate hypertension and children insomnia. These results highlight once again that LAB potential in ensuring food safety, food nutraceutical value and ultimately in favoring human health is still underexplored and underexploited.

Keywords: Lactobacillus helveticus 4D5; Lactobacillus rhamnosus 17D10; Lactococcus lactis; Nisin Z. Lactobacillus sakei I151; Sakacin; antimicrobial peptides; casein; lactic acid; mass spectrometry.

Figure 1

Identification of the NisZ gene at 174 bp, for the strain L. lactis 41FLL. M = molecular markers, Lane 1 = L. lactis 41FLL, Lane 2 = negative control.

Figure 2

Tricine-SDS-PAGE Coomassie stained gel of purified Nisin Z and Sakacin P. Panel (A): antimicrobial fractions of L. lactis 41FLL3 grown in M17 enriched with fructose (2% w/v) (1) and with glucose (2% w/v) (2). Panel (B): antimicrobial fraction of L. sakei I151 after purification with cation exchange column (3) and hydrophobic interaction column (4). M: marker.

Figure 3

Percentage of casein-derived peptides harvested in the late exponential phase of L. lactis MG1363, L. rhamnosus 17D10 and L. helveticus 4D5 growth curves.

Figure 4

Peptide coverage of the four caseins digested by L. lactis MG1363 (black), L. rhamnosus 17D10 (red) and L. helveticus 4D5 (green). Peptides with established bioactivity are underlined in yellow.