Inhibitory activity of Lactobacillus plantarum LMG P-26358 against Listeria innocua when used as an adjunct starter in the manufacture of cheese

Susan Mills,Carmel Griffin,Rpaul Ross,Chris Bruining,Wilco C Meijer,Colin Hill,Paula M O'Connor,Gwenda Schaad,Lmariela Serrano

doi:10.1186/1475-2859-10-s1-s7

Abstract

Lactobacillus plantarum LMG P-26358 isolated from a soft French artisanal cheese produces a potent class IIa bacteriocin with 100% homology to plantaricin 423 and bacteriocidal activity against Listeria innocua and Listeria monocytogenes. The bacteriocin was found to be highly stable at temperatures as high as 100°C and pH ranges from 1-10. While this relatively narrow spectrum bacteriocin also exhibited antimicrobial activity against species of enterococci, it did not inhibit dairy starters including lactococci and lactobacilli when tested by well diffusion assay (WDA). In order to test the suitability of Lb. plantarum LMG P-26358 as an anti-listerial adjunct with nisin-producing lactococci, laboratory-scale cheeses were manufactured. Results indicated that combining Lb. plantarum LMG P-26358 (at 108 colony forming units (cfu)/ml) with a nisin producer is an effective strategy to eliminate the biological indicator strain, L. innocua. Moreover, industrial-scale cheeses also demonstrated that Lb. plantarum LMG P-26358 was much more effective than the nisin producer alone for protection against the indicator. MALDI-TOF mass spectrometry confirmed the presence of plantaricin 423 and nisin in the appropriate cheeses over an 18 week ripening period. A spray-dried fermentate of Lb. plantarum LMG P-26358 also demonstrated potent anti-listerial activity in vitro using L. innocua. Overall, the results suggest that Lb. plantarum LMG P-26358 is a suitable adjunct for use with nisin-producing cultures to improve the safety and quality of dairy products.

Highlights

Bacteriocins are ribosomally synthesized, heat stable, antimicrobial peptides which are produced by a wide variety of bacteria
Isolation of Lactobacillus plantarum LMG P-26358 and bacteriocin assays Lb. plantarum LMG P-26358 was initially isolated from French artisanal cheese as follows: approximately 1g of cheese was homogenized in 9 mls of maximum recovery diluent (MRD), serially diluted and plated on MRS agar (Difco Laboratories, Detroit, MI, USA) and grown at 30°C for 2-3 days
Isolation and identification of Lactobacillus plantarum LMG P-26358 Lb. plantarum was isolated from a soft French artisanal cheese due to its associated production of a large zone from the colony when overlaid with L. innocua

Summary

Introduction

Bacteriocins are ribosomally synthesized, heat stable, antimicrobial peptides which are produced by a wide variety of bacteria. The bacteriocins of lactic acid bacteria (LAB) have been the topic of much interest in terms of food safety due to their “generally recognised as safe” (GRAS) status [2]. They have been classified into as many as three different groups based on their biochemical and genetic properties [3]. The well known bacteriocin nisin is a member of the class I group of bacteriocins These peptides are referred to as lantibiotics as they contain unusual amino acid derivatives such as lanthionine and/or b-methylanthionine as well as other posttranslational modifications. Class II contains unmodified peptides and are further subdivided into three subclasses; class IIa (one-peptide pediocin-like bacteriocins), class IIb (two-peptide bacteriocins), and class IIc (other nonpediocin-like one-peptide bacteriocins), while class III peptides consist of the thermosensitive proteins [4]

Methods

Results

Conclusion