Synergistic antimicrobial effect of lactocin AL705 and nisin combined with organic acid salts against Listeria innocua 7 in broth and a hard cheese

The effectiveness of antimicrobial mixtures against Listeria innocua 7, used as a L. monocytogenes surrogate, was investigated in broth and a food system. Synergistic effects were found for nisin (Nis), potassium sorbate (PS), calcium propionate (CP) and sodium lactate (SL), Nis + PS being the most effective binary mixture that exhibited listericidal activity in broth. To assess the effect of adding lactocin AL705 (AL705) to Nis + organic acid salt combinations, tridimensional isobolograms were generated. Sub-MIC combinations of the antimicrobials exerted bactericidal activity against L. innocua 7 after AL705 addition to the binary mixtures. However, when applied on Sardo cheese contaminated with L. innocua 7 (initial inoculum 4.45 ± 0.06 CFU g⁻¹), only Nis + PS + AL705 produced count reductions respect to the control, reaching 3.04 ± 0.35 CFU g⁻¹ counts after 15 days at 15 °C. Ternary combinations containing AL705 showed potential to reduce antimicrobial usages for L. innocua 7 inhibition.     

Nisin as a Food Preservative: Part 1: Physicochemical Properties,Antimicrobial Activity,and Main Uses

Nisin is a natural preservative for many food products. This bacteriocin is mainly used in dairy and meat products. Nisin inhibits pathogenic food borne bacteria such as Listeria monocytogenes and many other Gram-positive food spoilage microorganisms. Nisin can be used alone or in combination with other preservatives or also with several physical treatments. This paper reviews physicochemical and biological properties of nisin, the main factors affecting its antimicrobial effectiveness, and its food applications as an additive directly incorporated into food matrices.     

Biochemical,Structural, and Genetic Characterization of Tridecaptin A1, an Antagonist of Campylobacter jejuni

Bacillus circulans NRRL B‐30644 (now Paenibacillus terrae) was previously reported to produce SRCAM 1580, a bacteriocin active against the food pathogen Campylobacter jejuni. We have been unable to isolate SRCAM 1580, and did not find any genetic determinants in the genome of this strain. We now report the reassignment of this activity to the lipopeptide tridecaptin A₁. Structural characterization of tridecaptin A₁ was achieved through NMR, MS/MS and GC‐MS studies. The structure was confirmed through the first chemical synthesis of tridecaptin A₁, which also revealed the stereochemistry of the lipid chain. The impact of this stereochemistry on antimicrobial activity was examined. The biosynthetic machinery responsible for tridecaptin production was identified through bioinformatic analyses. P. terrae NRRL B‐30644 also produces paenicidin B, a novel lantibiotic active against Gram‐positive bacteria. MS/MS analyses indicate that this lantibiotic is structurally similar to paenicidin A.     

Production of Bioactive Peptides from Lactic Acid Bacteria: A Sustainable Approach for Healthier Foods

Traditional fermented foods where lactic acid bacteria (LAB) are present have been associated with beneficial effects on human health, and some of those benefits are related to protein‐derived products. Peptides produced by LAB have attracted the interest of food industries because of their diverse applications. These peptides include ribosomally produced (bacteriocins) and protein hydrolysates by‐products (bioactive peptides), which can participate as natural preservatives and nutraceuticals, respectively. It is essential to understand the biochemical pathways and the effect of growth conditions for the production of bioactive peptides and bacteriocins by LAB, in order to suggest strategies for optimization. LAB is an important food‐grade expression system that can be used in the simultaneous production of peptide‐based products for the food, animal, cosmetic, and pharmaceutical industries. This review describes the multifunctional proteinaceous compounds generated by LAB metabolism and discusses a strategy to use a single‐step production process, using an alternative protein‐based media. This strategy will provide economic advantages in fermentation processes and will also provide an environmental alternative to industrial waste valorization. New technologies that can be used to improve production and bioactivity of LAB‐derived peptides are also analyzed.     

Class IIa bacteriocins from lactic acid bacteria: antibacterial activity and food preservation

In the last decade, a variety of ribosomally synthesized antimicrobial peptides, or bacteriocins, produced by lactic acid bacteria have been identified and characterized. As a result of these studies, insight has been gained into various fundamental aspects of biology and biochemistry such as bacteriocin processing and secretion, mechanisms of cell immunity, and structure-function relationships. In parallel, there has been a growing awareness that bacteriocins may be developed into useful antimicrobial food additives. Class IIa bacteriocins can be considered as the major subgroup of bacteriocins from lactic acid bacteria, not only because of their large number, but also because of their significant biological activities and potential applications. The present review provides an overview of the knowledge available for class IIa bacteriocins and discusses common features and recent findings concerning these substances. The activity and potential food applications of class IIa bacteriocins are a major focus of this review.     

无前导肽细菌素的研究进展及在食品保藏中的应用

细菌素作为食品防腐剂在食品工业中已广泛应用。无前导肽细菌素是一类由核糖体合成、不进行任何翻译后修饰、N端没有前导肽序列的细菌素。该文对目前无前导肽细菌素的类型、生物合成、理化特征、抗菌机制及在食品保藏中的应用进行综述。分析表明,该类细菌素通常含27个~53个氨基酸,富含赖氨酸残基而缺少半胱氨酸残基,均带有正电荷,有较高的等电点;该类细菌素受受体影响小,静电作用和疏水作用在抑菌机制中发挥重要作用,多数具有广谱抑菌活性;该类细菌素遗传结构简单,便于在其它微生物中表达,易于规模化生产。     

乳酸菌中共培养诱导细菌素产生机制的研究进展

众所周知,一些乳酸菌拥有产生抗菌化合物的能力,一般采用分离单一培养物和抑制特定靶标微生物的方法筛选产生抗菌化合物的微生物,揭示诱导微生物抗菌活性产生的一个重要策略就是通过与其他微生物共培养。目前为止,已有一些研究探讨了共培养诱导细菌素产生的特性,发现产细菌素微生物和诱导细菌素微生物之间没有明显的关系。同时对于这种微生物间相互作用的分子机制研究有所突破,发现群体感应系统在细菌素产生中发挥重要作用,但还未鉴定或表征其中的诱导化合物。然而,在一些例子中,通用信使分子——自诱导物-2的存在与共培养诱导细菌素这种表型相关,并且其可在群体感应系统的调节中起作用。了解共培养的诱导机制将有助于筛选和开发共培养细菌素产生系统和新产品的策略,以及这种系统在食物和肠道中的定植能力,从而增加益生菌对宿主的益生功效。     

Characterization of a multilayer film activated with Lactobacillus curvatus CRL705 bacteriocins

BACKGROUND: Bacteriocins produced by lactic acid bacteria offer enormous promise for food safety preservation. In this study an active multilayer film obtained by the incorporation of lactocin 705 and lactocin AL705, two bacteriocins produced by Lactobacillus curvatus CRL705 with antimicrobial activity against Lactobacillus plantarum CRL691 and Listeria innocua 7, respectively, was characterized for its potential application in active packaging technology. Film activity performance at different storage conditions, bacteriocins transfer into water and sunflower oil, and film surface properties were evaluated. RESULTS: Film activity against L. innocua 7 was maintained during 2, 4 and 6 weeks at 30, 10 and 5 °C respectively. At 30 and 10 °C, activity loss against L. plantarum CRL691 was observed on the second week of storage and after the fourth week at 5 °C. Results showed no significant difference for active multilayer film contact angle and seal properties compared to the control (without bacteriocins). A decrease in lactocin 705 inhibitory activity after sunflower oil contact was observed, while lactocin AL705 remained unaffected. After water contact, film activity was retained for both bacteriocins. CONCLUSIONS: As demonstrated by antimicrobial activity and physico‐mechanical properties retention, lactocin 705 and AL705 active multilayer film present potential for application in active packaging technology. Copyright © 2011 Society of Chemical Industry     

Functional Properties of Lactic Acid Bacteria Isolated from Romanian Fermented Vegetables

A total of 139 lactic acid bacterium (LAB) strains isolated from Romanian traditionally fermented vegetables were screened for the ability to produce exopolysaccharides and for their antagonistic activity against a set of nine LAB strains, three Bacillus strains, and four Gram-negative bacteria. Eighty-five of the tested strains showed a variable antimicrobial activity against Listeria monocytogenes ATCC 1911, 35 of the strains showed a limited inhibition zone against Escherichia coli ATCC25922, and 26 strains against Salmonella enterica ATCC 14024, while 19 strains showed inhibition against one or all three Bacillus strains used as indicators. None of the tested strains showed an antimicrobial activity against Staphylococcus aureus ATCC 25923. Several strains showed antibacterial activity against more than one indicator strain. For instance, Lactobacillus plantarum 307, Lactobacillus brevis 308, and Lactobacillus plantarum/pentosus 358 were active against five of the indicator strains used, while other 23 LAB were active against three indicator strains. In the case of two strains, namely Leuconostoc citreum 344 and Lactobacillus brevis 183, the activity was maintained after neutralizing the pH of the cell-free supernatant likely due to the production of bacteriocins. The gel permeation chromatography-based screening revealed seven EPS-producing LAB strains. Two of the positive strains, namely Leuconostoc citreum 177 and Leuconostoc citreum 52, have been shown to produce large amounts of EPS, of about 20 g/L. All isolated EPS have a high molecular mass, of above 1400 KDa, and a monomer composition dominated by the presence of glucose.     

Microbes versus microbes: control of pathogens in the food chain

Foodborne illness continues as a considerable threat to public health. Despite improved hygiene management systems and increased regulation, pathogenic bacteria still contaminate food, causing sporadic cases of illness and disease outbreaks worldwide. For many centuries, microbial antagonism has been used in food processing to improve food safety. An understanding of the mode of action of this microbial antagonism has been gained in recent years and potential applications in food and feed safety are now being explored. This review focuses on the potential opportunities presented, and the limitations, of using microbial antagonism as a biocontrol mechanism to reduce contamination along the food chain; including animal feed as its first link. © 2014 Society of Chemical Industry