Abstract
Micrococcus luteus, Listeria monocytogenes, and Bacillus cereus are major food-borne pathogenic and spoilage bacteria. Emergence of antibiotic resistance and consumer demand for foods containing less of chemical preservatives led to a search for natural antimicrobials. A study aimed at characterizing, investigating the mechanism of action and regulation of biosynthesis and evaluating the biopreservative potential of pentocin from Lactobacillus pentosus CS2 was conducted. Pentocin MQ1 is a novel bacteriocin isolated from L. pentosus CS2 of coconut shake origin. The purification strategy involved adsorption-desorption of bacteriocin followed by RP-HPLC. It has a molecular weight of 2110.672 Da as determined by MALDI-TOF mass spectrometry and a molar extinction value of 298.82 M−1 cm−1. Pentocin MQ1 is not plasmid-borne and its biosynthesis is regulated by a quorum sensing mechanism. It has a broad spectrum of antibacterial activity, exhibited high chemical, thermal and pH stability but proved sensitive to proteolytic enzymes. It is potent against M. luteus, B. cereus, and L. monocytogenes at micromolar concentrations. It is quick-acting and exhibited a bactericidal mode of action against its targets. Target killing was mediated by pore formation. We report for the first time membrane permeabilization as a mechanism of action of the pentocin from the study against Gram-positive bacteria. Pentocin MQ1 is a cell wall-associated bacteriocin. Application of pentocin MQ1 improved the microbiological quality and extended the shelf life of fresh banana. This is the first report on the biopreservation of banana using bacteriocin. These findings place pentocin MQ1 as a potential biopreservative for further evaluation in food and medical applications.
Highlights
Consumer’s requisition for food products containing less chemical preservatives (Barbosa et al, 2017) and emergence of antibiotic resistance among pathogenic and food spoilage bacteria prompted the search for novel antimicrobials (Berendonk et al, 2015; Jia et al, 2017)
Enterococcus faecium American Type Culture Collection (ATCC) BAA-2127 and E. faecium ATCC 349 were maintained on Tryptic soy agar (Merck, Darmstadt, Germany) while other enterococcal strains and L. monocytogenes National Collection of Type Culture (NCTC) 10890 were maintained on Brainheart infusion agar (Merck, Darmstadt, Germany)
L. pentosus CS2 has been isolated from vagina (Okkers et al, 1999), fermented Xuan-Wei ham (Zhang et al, 2009) and fermented shrimp (Watthanasakphuban et al, 2016), this is the first report of its isolation from coconut shake considered as a dairy product
Summary
Consumer’s requisition for food products containing less chemical preservatives (Barbosa et al, 2017) and emergence of antibiotic resistance among pathogenic and food spoilage bacteria prompted the search for novel antimicrobials (Berendonk et al, 2015; Jia et al, 2017). Pentocin MQ1, a Novel Bacteriocin combination with antibiotics or complete replacement of antibiotics (Behrens et al, 2017; Collins et al, 2017) and currently used chemical preservatives (Kaškoniene et al, 2017; Wiernasz et al, 2017) This is due to their ability to inhibit some drugresistant pathogens (Mathur et al, 2017). Bacteriocins are a highly diverse group of antimicrobial peptides They have variations in molecular weight, inhibitory spectrum, mode of action, mechanism of biosynthesis and externalization, and self-protection mechanism (Salazar et al, 2017). They are inactivated by gut proteases, heat-stable, active at various pH, potent even at nanomolar concentration and their biosynthetic gene cluster is often plasmid-borne, facilitating the use genetic engineering approaches in improving production (Cotter et al, 2013; Lakshminarayanan et al, 2013; Messaoudi et al, 2013; Woraprayote et al, 2016)
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