Antimicrobial activity of nisin against Oenococcus oeni and other wine bacteria

Antimicrobial Compounds in Wine

Ipsum vinum est potestas et possession (wine itself is power and possession). Wine is a complex system that triggers multisensory cognitive stimuli. Wine and its consumption are thoroughly intertwined with the development of human society. The beverage was appreciated in many ancient mythologies and plays an essential part in Christianity and rituals to this day. Wine has been said to enlighten and inspire artists and has even been prohibited by law and some religions, but has nevertheless played a role in human civilizations since the beginning. Winemaking is also a prospering and economically important industry and a longtime symbol of status and luxury. In winemaking, the formation of the final product is influenced by several factors that contribute to the chemical and sensory complexity often associated with quality vintages. Factors such as terroir, climatic conditions, variety of the grape, all aspects of the winemaking process to the smallest details, including metabolic processes carried out by yeast and malolactic bacteria, and the conditions for the maturation and storage of the final product, up to, and even beyond the point of deciding to open the bottle and enjoy the wine. In conjunction with the empiric and scientific process of winemaking, different molecules with antibacterial activity can be identified in wine during the production process, and several of them are clearly present in the final product. Some of these antibacterial components are phytochemicals, such as flavonoids and phenolic compounds, that may be delivered to the final product (wine) as a part of the grape, a variety of potential additive compounds, or from the oak barrels or clay amphoras used during the maturation process. Others are produced by yeasts and malolactic bacteria and play a role not only in the moderation of the fermentation process but contributing to the microbiological safety and beneficial properties spectra of the final product. Lactic acid bacteria, responsible for conducting malolactic fermentation, contribute to the final balance of the wine but are also directly involved in the production of different compounds exhibiting antibacterial activity. Some examples of these compounds include bacteriocins (antibacterial peptides), diacetyl, organic acids, reuterin, hydrogen peroxide, and carbon dioxide. Major aspects of these different beneficial metabolites are the subject of discussion in this review with the aim of highlighting their beneficial functions.

Antimicrobial activities of Asian plant extracts against pathogenic and spoilage bacteria

This study was conducted to investigate the antimicrobial effects of 300 Asian plant extracts (PEs) against pathogenic and spoilage bacteria. The antimicrobial activities were examined using agar well or agar disc diffusion, and micro-titer methods. Results revealed that PEs exhibited higher antimicrobial effects against Gram-positive bacteria compared than against Gram-negative bacteria. With few exceptions, PEs delayed the lag time (LT) of pathogenic bacteria (1.17-3.75 times). Among PEs tested, Alchornea trewioides (AT) and Erodium stephanianum (ES) were the most effective in inhibiting pathogenic and spoilage bacteria. In the study evaluating the effect on the growth inhibition in the broth, Acetobacter aceti was inhibited at 2.77 and 3.02 log CFU/mL by the combination treatment of AT+nisin and ES+nisin after storage for 7 days, respectively. Although further investigations are needed to clarify the antimicrobial mechanism of PEs, this study demonstrated that antimicrobial efficacy varied with PE types, solvents, and bacteria.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01182-0.

Prospects of antimicrobial peptides as an alternative to chemical preservatives for food safety

Antimicrobial peptides (AMPs) are a potential alternative to antimicrobial agents that have got considerable research interest owing to their significant role in the inhibition of bacterial pathogens. These AMPs can essentially inhibit the growth and multiplication of microbes through multiple mechanisms including disruption of cellular membranes, inhibition of cell wall biosynthesis, or affecting intracellular components and cell division. Moreover, AMPs are biocompatible and biodegradable therefore, they can be a good alternative to antimicrobial agents and chemical preservatives. A few of their features for example thermostability and high selectivity are quite appealing for their potential use in the food industry for food preservation to prevent the spoilage caused by microorganisms and foodborne pathogens. Despite these advantages, very few AMPs are being used at an industrial scale for food preservation as these peptides are quite vulnerable to external environmental factors which deter their practical applications and commercialization. The review aims to provide an outline of the mechanism of action of AMPs and their prospects as an alternative to chemical preservatives in the food industry. Further studies related to the structure-activity relationship of AMPs will help to expand the understanding of their mechanism of action and to determine specific conditions to increase their stability and applicability in food preservation.

Bioprotection strategies in winemaking

Worldwide the interest for biological control of food spoilage microorganisms has significantly increased over the last decade. Wine makes no exception to this trend, as consumer demands for wines free of preservatives that are considered negative for human health, increase. Biological control during wine fermentation aims at producing high quality wines, while minimizing, or even eliminating, the use of chemical additives. Its success lies in the inoculation of microorganisms to prevent, inhibit or kill undesired microbes, therefore maintaining wine spoilage at the lowest level. The food industry already makes use of this practice, with dedicated commercial microbes already on the market. In winemaking, there are commercial microbes currently under investigation, particularly with the aim to reduce or replace the use of sulphur dioxide. In this review, the potential of wine yeasts and lactic acid bacteria as bioprotection agents and their mechanisms of action during wine fermentation are presented.

Antimicrobial plant secondary metabolites, MDR transporters and antimicrobial resistance in cereal-associated lactobacilli: is there a connection?

Cereal-associated lactobacilli resist antimicrobial plant secondary metabolites. This study aimed to identify multi-drug-resistance (MDR) transporters in isolates from mahewu, a Zimbabwean fermented cereal beverage, and to determine whether these MDR-transporters relate to resistance against phenolic compounds and antibiotics. Comparative genomic analyses indicated that all seven mahewu isolates harbored multiple MATE and MFS MDR proteins. Strains of Lactiplantibacillus plantarum and Limosilactobacillus fermentum encoded for the same gene, termed mahewu phenolics resistance gene mprA, with more than 99% nucleotide identity, suggesting horizontal gene transfer. Strains of Lp. plantarum were more resistant than strains of Lm. fermentum to phenolic acids, other antimicrobials and antibiotics but the origins of strains were not related to resistance. The resistance of several strains exceeded EFSA thresholds for several antibiotics. Analysis of gene expression in one strain each of Lp. plantarum and Lm. fermentum revealed that at least one MDR gene in each strain was over-expressed during growth in wheat, sorghum and millet relative to growth in MRS5 broth. In addition, both strains over-expressed a phenolic acid reductase. The results suggest that diverse lactobacilli in mahewu share MDR transporters acquired by lateral gene transfer, and that these transporters mediate resistance to secondary plant metabolites and antibiotics.

Analysis of Transcriptomic Response to SO2 by Oenococcus oeni Growing in Continuous Culture

To successfully complete malolactic fermentation (MLF), Oenococcus oeni must overcome wine stress conditions of low pH, high ethanol, and the presence of SO2. Failure to complete MLF may result in detrimental effects to the quality and stability of the resulting wines. Research efforts to date have focused on elucidating the mechanisms and genetic features that confer the ability to withstand low pH and high ethanol concentrations on O. oeni; however, the responses to SO2 stress are less well defined. This study focused on characterizing the transcriptional response of O. oeni to SO2 challenge during cultivation in a continuous system at wine-like pH (3.5). This experimental design allowed the precise discrimination of transcriptional changes linked to SO2 stress from responses associated with growth stage and cultivation parameters. Differential gene expression analysis revealed major transcriptional changes following SO2 exposure and suggested that this compound primarily interacts with intracellular proteins, DNA, and the cell envelope of O. oeni. The molecular chaperone hsp20, which has a demonstrated function in the heat, ethanol, and acid stress response, was highly upregulated, confirming its additional role in the response of this species to SO2 stress. This work also reports the first nanopore-based complete genome assemblies for O. oeni. IMPORTANCE Malolactic fermentation is an indispensable step in the elaboration of most wines and is generally performed by Oenococcus oeni, a Gram-positive heterofermentative lactic acid bacterium species. While O. oeni is tolerant to many of the wine stresses, including low pH and high ethanol concentrations, it has high sensitivity to SO2, an antiseptic and antioxidant compound regularly used in winemaking. Understanding the physiological changes induced in O. oeni by SO2 stress is essential for the development of more robust starter cultures and methods for their use. This study describes the main transcriptional changes induced by SO2 stress in the wine bacterium O. oeni and provides foundational understanding on how this compound interacts with the cellular components and the induced protective mechanisms of this species.

Bioactive Peptides: A Promising Alternative to Chemical Preservatives for Food Preservation

Bioactive peptides used for food preservation can prolong the shelf life through bacteriostasis and antioxidation. On the one hand, bioactive peptides can inhibit lipid oxidation by scavenging free radicals, interacting with metal ions, and inhibiting lipid peroxidation. On the other hand, bioactive peptides can fundamentally inhibit the growth and reproduction of microorganisms by destroying their cell membranes or targeting intracellular components. Besides, bioactive peptides are biocompatible and biodegradable in vivo. Therefore, they are regarded as a promising alternative to chemical preservatives. However, bioactive peptides are easily affected by the external environment in practical application, which hinders their commercialization. Currently, the studies to overcome the weakness focus on encapsulation and chemical synthesis. Bioactive peptides have been applied to the preservation of various foods in experimental research, with good results. In the future, with the deepening understanding of their safety and structure-activity relationship, there may be more bioactive peptides as food preservatives.

Production of a Class IIb Bacteriocin with Broad-spectrum Antimicrobial Activity in Lactiplantibacillus plantarum RUB1

Bacteriocins produced by lactic acid bacteria have potential use as natural food preservatives, which may alleviate current problems associated with the overuse of antibiotics and emerging multi-drug-resistant microbes. In this work, Lactiplantibacillus plantarum RUB1 was found to produce a class IIb bacteriocin with strong antibacterial activity. Except for plnXY encoding putative proteins, L. plantarum RUB1 contains most genes in five operons (plnABCD, plnGHSTUVW, plnMNOP, plnIEF, and plnRLJK) related to bacteriocin synthesis. Adding low (100 and 500 ng/mL) and medium (1 μg/mL) concentrations of PlnA to broth promoted bacteriocin production and upregulated bacteriocin gene plnA, while high concentrations (50 and 200 μg/mL) inhibited expression of these genes. Co-culturing L. plantarum RUB1 with Enterococcus hirae 1003, Enterococcus hirae LWS, Limosilactobacillus fermentum RC4, L. plantarum B6, and even Listeria monocytogenes ATCC 19111 and Staphylococcus aureus ATCC 6538 enhanced bacteriocin activity and expression of bacteriocin-related genes. This study verifies that PlnA can indeed upregulate the expression of bacteriocin genes, and also bacteriocin production can be induced by co-culture with some specific bacteria or their cell-free supernatants. Bacteriocin production by L. plantarum RUB1 is mediated by a quorum sensing mechanism, directly influenced by autoinducing peptide or specific strains. The findings provide new methods and insight into bacteriocin production mechanisms.

Biofilm-Forming Ability and Effect of Sanitation Agents on Biofilm-Control of Thermophile Geobacillus sp. D413 and Geobacillus toebii E134

Geobacillus sp. D413 and Geobacillus toebii E134 are aerobic, non-pathogenic, endospore-forming, obligately thermophilic bacilli. Gram-positive thermophilic bacilli can produce heat-resistant spores. The bacteria are indicator organisms for assessing the manufacturing process’s hygiene and are capable of forming biofilms on surfaces used in industrial sectors. The present study aimed to determine the biofilm-forming properties of Geobacillus isolates and how to eliminate this formation with sanitation agents. According to the results, extracellular DNA (eDNA) was interestingly not affected by the DNase I, RNase A, and proteinase K. However, the genomic DNA (gDNA) was degraded by only DNase I. It seemed that the eDNA had resistance to DNase I when purified. It is considered that the enzymes could not reach the target eDNA. Moreover, the eDNA resistance may result from the conserved folded structure of eDNA after purification. Another assumption is that the eDNA might be protected by other extracellular polymeric substances (EPS) and/or extracellular membrane vesicles (EVs) structures. On the contrary, DNase I reduced unpurified eDNA (mature biofilms). Biofilm formation on surfaces used in industrial areas was investigated in this work: the D413 and E134 isolates adhered to all surfaces. Various sanitation agents could control biofilms of Geobacillus isolates. The best results were provided by nisin for D413 (80%) and α-amylase for E134 (98%). This paper suggests that sanitation agents could be a solution to control biofilm structures of thermophilic bacilli.

Study on the Inhibitory Activity of a Synthetic Defensin Derived from Barley Endosperm against Common Food Spoilage Yeast

In the food industry, food spoilage is a real issue that can lead to a significant amount of waste. Although current preservation techniques are being applied to reduce the occurrence of spoilage microorganisms, the problem persists. Food spoilage yeast are part of this dilemma, with common spoilers such as Zygosaccharomyces, Kluyveromyces, Debaryomyces and Saccharomyces frequently encountered. Antimicrobial peptides derived from plants have risen in popularity due to their ability to reduce spoilage. This study examines the potential application of a synthetic defensin peptide derived from barley endosperm. Its inhibitory effect against common spoilage yeasts, its mechanisms of action (membrane permeabilisation and overproduction of reactive oxygen species), and its stability in different conditions were characterised. The safety of the peptide was evaluated through a haemolysis and cytotoxicity assay, and no adverse effects were found. Both assays were performed to understand the effect of the peptide if it were to be consumed. Its ability to be degraded by a digestive enzyme was also examined for its safety. Finally, the peptide was successfully applied to different beverages and maintained the same inhibitory effects in apple juice as was observed in the antiyeast assays, providing further support for its application in food preservation.

Biotechnological Approach Based on Selected Saccharomyces cerevisiae Starters for Reducing the Use of Sulfur Dioxide in Wine

Sulfites are considered the main additives in winemaking for their antimicrobial, antioxidant and anti-oxidasic activities. The current concern about the potential negative effects of sulfur dioxide (SO2) on consumer health has focused the interest on replacing or reducing SO2 use. Our work aims to develop a strategy based on the use of selected starter culture, able to perform wine fermentation without SO2 addition. Four selected Saccharomyces cerevisiae indigenous strains were tested as mixed starter cultures in laboratory scale fermentations. The starter culture, characterized by a similar percentage of dominance of both strains composing the mixed starter and able to produce a wine characterized by the best combination of chemical and aromatic characteristics, was chosen. This mixed culture was tested as a starter at pilot scale with and without SO2 addition, by using a higher inoculum level in the vinification without SO2. The selected starter confirmed higher dominance ability in vinification without SO2 addition than in SO2-added fermentation, demonstrating that sulfite addition is not a guarantee to reach an absolute dominance of starter culture on indigenous microflora. The proposed biotechnological tool allowed to produce good quality wines possessing also "functional properties", as NO-SO2 added wines were characterized by high polyphenol content and antioxidant activity.

Bacteriophages as an Up-and-Coming Alternative to the Use of Sulfur Dioxide in Winemaking

Certain acetic and lactic acid bacteria are major causes of quality defects in musts and wines, giving rise to defects such as a "vinegary," "sharp, like nail polish-remover" taste or preventing alcoholic and/or malolactic fermentation. Sulfur dioxide is the major tool currently used in the control of these bacteria in wine. The aim of this work was to isolate bacteriophages from musts and wine of different grape varieties that were able to eliminate lactic and acetic acid bacteria spoilages at the laboratory scale. Musts obtained from grape-berries of Vitis vinifera cv. Chardonnay and Moscatel and a red wine made with V. vinifera cv. Tintilla de Rota were used to isolate bacteriophages. Bacteriophages were obtained from each of the musts and the wine and belonged to the order Caudovirals and the family Tectivirals. They were isolated by classical virology methods and identified by electron microscopy. The host bacteria used in the study were lactic acid bacteria of the species Lactobacillus hilgardii, Lactobacillus plantarum, and Oenococcus oeni and the acetic bacteria Acetobacter aceti. A comparative study was performed by adding phage titrations and SO2 to musts and wines, which had been previously inoculated with bacteria, to study the effectiveness of bacteriophages against bacteria. The comparative study showed that some bacteriophages were as effective as sulfur dioxide at low concentrations.

Chemical hazards in grapes and wine, climate change and challenges to face

Climate change has an impact on the chemical risks associated to wine consumption related with grape development and microbial contamination. We can classify chemical hazards in wine into two groups: those present in grapes due to agricultural practices, environmental contamination or fungal growth and those coming from fermentation and the winemaking process. The first group includes mycotoxins, whilst the second encompasses ethyl carbamate, biogenic amines, sulfur dioxide and proteins used as technological ingredients such as fining material. Usually the effective control of chemical hazards is achieved by assuring that they either are minimized or absent in the final product since their removal is somewhat difficult and sometimes it may affect sensory properties, which is a major issue in wine. Interestingly, it is possible to give recommendations to avoid excess of these compounds, but more research is needed to face future challenges related to climate change and consumer demands.

Alternative Methods to SO2 for Microbiological Stabilization of Wine

The use of sulfur dioxide (SO₂ ) as wine additive is able to ensure both antioxidant protection and microbiological stability. In spite of these undeniable advantages, in the last two decades the presence of SO₂ in wine has raised concerns about potential adverse clinical effects in sensitive individuals. The winemaking industry has followed the general trend towards the reduction of SO₂ concentrations in food, by expressing at the same time the need for alternative control methods allowing reduction or even elimination of SO_2. In the light of this, research has been strongly oriented toward the study of alternatives to the use of SO₂ in wine. Most of the studies have focused on methods able to replace the antimicrobial activity of SO₂ . This review article gives a comprehensive overview of the current state-of-the-art about the chemical additives and the innovative physical techniques that have been proposed for this purpose. After a focus on the chemistry and properties of SO₂ in wine_, as well as on wine spoilage and on the conventional methods used for the microbiological stabilization of wine, recent advances on alternative methods proposed to replace the antimicrobial activity of SO₂ in winemaking are presented and discussed. Even though many of the alternatives to SO₂ showed good efficacy, nowadays no other physical technique or additive can deliver the efficacy and broad spectrum of action as SO₂ (both antioxidant and antimicrobial), therefore the alternative methods should be considered a complement to SO₂ in low-sulfite winemaking, rather than being seen as its substitutes.

Production and Antimicrobial Activity of Nisin Under Enological Conditions

Lactic acid bacteria (LAB) are responsible for the malolactic fermentation of wines, and, therefore, controlling the growth of these bacteria is a key factor for elaborating premium wines. Sulfur dioxide has been traditionally used as an efficient antimicrobial and antioxidant agent, however, nowadays consumers' demand tends toward a reduction of sulfur dioxide levels in wine and other fermented foods. A previous study of our research group had demonstrated the effectiveness of the bacteriocin nisin to inhibit the growth of enological LAB, and its activity had been tested in culture broths. The aim of this study was to investigate the possibility of controlling the growth of bacteria in wine by the use of nisin in combination with sulfur dioxide, and to study nisin production by the natural producer Lactococcus lactis LM29 under enological conditions. Our results showed that L. lactis LM29 produced nisin in the presence of 2 and 4% ethanol (v/v), while higher concentrations of ethanol fully inhibited the production of nisin. We obtained a nisin enriched active extract (NAE) from the cell-free supernatant of a culture of L. lactis LM29 in MRS broth containing 60% (v/v) sterile grape juice, and the extract was fully active in inhibiting the growth of the enological LAB tested by the microtiter method. Moreover, the nisin concentration of the obtained NAE could actually prevent the formation of an undesirable biofilm of LAB strains. Finally, our results of wine ageing under winery conditions showed that the use of 50 mg/L nisin decreased fourfold the concentration of sulfur dioxide required to prevent LAB growth in the wines.

In silico Logistic Model for Table Olive Related Microorganisms As a Function of Sodium Metabisulphite, Cinnamaldehyde, pH, and Type of Acidifying Agent

A probabilistic/logistic model, based on binary data (growth/no growth), was used to assess the effects of sodium metabisulphite (SM) and cinnamaldehyde (CIN; 0-1000 mg/L) against the main microbial groups found in table olive environment [lactic acid bacteria (LAB), yeasts, and Enterobacteriaceae], according to pH (range 3.5-5.0), and type of acidifying agent (HCl or pyruvic acid). The inhibitory effect of SM depended on the pH while that of CIN was scarcely influenced by it (except for LAB). LAB were more sensitive to SM, while yeasts were to CIN. The use of pyruvic acid for correction of pH always produced a reduction (compared to HCl) of the inhibitory power of both preservatives. The in silico models for HCl showed that, at pH 4.0, and growth probability 0.01, the LAB population might be inhibited by the presence in the medium of 150 mg/L SM or 1000 mg/L CIN, while in the case of yeasts, 450 mg/L SM, or 150 mg/L CIN are required. No growth of Enterobacteriaceae was observed at this (or lower) pH level. The results obtained may contribute to the stabilization of non-thermally treated table olive packaging.

Antimicrobial peptides as natural bio-preservative to enhance the shelf-life of food

Antimicrobial peptides (AMPs) are diverse group of natural proteins present in animals, plants, insects and bacteria. These peptides are responsible for defense of host from pathogenic organisms. Chemical, enzymatic and recombinant techniques are used for the synthesis of antimicrobial peptides. These peptides have been found to be an alternative to the chemical preservatives. Currently, nisin is the only antimicrobial peptide, which is widely utilized in the preservation of food. Antimicrobial peptides can be used alone or in combination with other antimicrobial, essential oils and polymeric nanoparticles to enhance the shelf-life of food. This review presents an overview on different types of antimicrobial peptides, purification techniques, mode of action and application in food preservation.

Identification of lactic acid bacteria isolated from wine using real-time PCR

Different lactic acid bacteria strains have been shown to cause wine spoilage, including the generation of substances undesirable for the health of wine consumers. The aim of this study was to investigate the occurrence of selected species of heterofermentative lactobacilli, specifically Lactobacillus brevis, Lactobacillus hilgardii, and Lactobacillus plantarum in six different Slovak red wines following the fermentation process. In order to identify the dominant Lactobacillus strain using quantitative (real time) polymerized chain reaction (qPCR) method, pure lyophilized bacterial cultures from the Czech Collection of Microorganisms were used. Six different red wine samples following malolactic fermentation were obtained from selected wineries. After collection, the samples were subjected to a classic plate dilution method for enumeration of lactobacilli cells. Real-time PCR was performed after DNA extraction from pure bacterial strains and wine samples. We used SYBR® Green master mix reagents for measuring the fluorescence in qPCR. The number of lactobacilli ranged from 3.60 to 5.02 log CFU mL(-1). Specific lactobacilli strains were confirmed by qPCR in all wine samples. The number of lactobacilli ranged from 10(3) to 10(6) CFU mL(-1). A melting curve with different melting temperatures (T(m)) of DNA amplicons was obtained after PCR for the comparison of T(m) of control and experimental portions, revealing that the most common species in wine samples was Lactobacillus plantarum with a T(m) of 84.64°C.

Antibacterial activity of hen egg white lysozyme modified by heat and enzymatic treatments against oenological lactic acid bacteria and acetic acid bacteria

The antimicrobial activity of heat-denatured and hydrolyzed hen egg white lysozyme against oenological lactic acid and acetic acid bacteria was investigated. The lysozyme was denatured by heating, and native and heat-denatured lysozymes were hydrolyzed by pepsin. The lytic activity against Micrococcus lysodeikticus of heat-denatured lysozyme decreased with the temperature of the heat treatment, whereas the hydrolyzed lysozyme had no enzymatic activity. Heat-denatured and hydrolyzed lysozyme preparations showed antimicrobial activity against acetic acid bacteria. Lysozyme heated at 90°C exerted potent activity against Acetobacter aceti CIAL-106 and Gluconobacter oxydans CIAL-107 with concentrations required to obtain 50% inhibition of growth (IC50) of 0.089 and 0.013 mg/ml, respectively. This preparation also demonstrated activity against Lactobacillus casei CIAL-52 and Oenococcus oeni CIAL-91 (IC50, 1.37 and 0.45 mg/ml, respectively). The two hydrolysates from native and heat-denatured lysozyme were active against O. oeni CIAL-96 (IC50, 2.77 and 0.3 mg/ml, respectively). The results obtained suggest that thermal and enzymatic treatments increase the antibacterial spectrum of hen egg white lysozyme in relation to oenological microorganisms.

Effect of high pressure treatments on the physicochemical properties of a sulphur dioxide-free red wine

The application of high hydrostatic pressure (HHP) in winemaking for substitution of the use of sulphur dioxide is still at a very early stage of development, since knowledge about the effect on physicochemical and sensorial characteristics of the wine during storage is very scarce. In this work, the evolution of colour, antioxidant activity and total phenolic compounds of SO2-free red wines treated by HHP and aged in bottles was followed for 12 months. The pressurised wines were compared with wine samples prepared with addition of 40 ppm of SO2 and without any of these two treatments. After 12 months, the pressurised wines presented higher values of CIELab parameters (a(*), b(*), and L(*)) and a lower monomeric anthocyanin content (45-61%) when compared to the unpressurised ones. The pressurised wines showed also a better global sensorial assessment, with the pressure treatments imparting aged-like characteristics to the wines. The wine deposits of pressurised wines had higher total phenolic content, namely proanthocyanidins (3- to 10-fold). The results demonstrate that HHP can influence long term red wine physicochemical and sensorial characteristics, hypothesised to be due to an increase of condensation reactions of phenolic compounds, forming compounds with higher degree of polymerisation that became insoluble in wine along storage.

In vitro antagonistic growth effects of Lactobacillus fermentum and lactobacillus salivarius and their fermentative broth on periodontal pathogens

As lactobacilli possess an antagonistic growth property, these bacteria may be beneficial as bioprotective agents for infection control. However, whether the antagonistic growth effects are attributed to the lactobacilli themselves or their fermentative broth remains unclear. The antagonistic growth effects of Lactobacillus salivarius and Lactobacillus fermentum as well as their fermentative broth were thus tested using both disc agar diffusion test and broth dilution method, and their effects on periodontal pathogens, including Streptococcus mutans, Streptococcus sanguis, and Porphyromonas gingivalis in vitro at different concentrations and for different time periods were also compared. Both Lactobacillus salivarius and Lactobacillus fermentum and their concentrated fermentative broth were shown to inhibit significantly the growth of Streptococcus mutans, Streptococcus sanguis, and Porphyromonas gingivalis, although different inhibitory effects were observed for different pathogens. The higher the counts of lactobacilli and the higher the folds of concentrated fermentative broth, the stronger the inhibitory effects are observed. The inhibitory effect is demonstrated to be dose-dependent. Moreover, for the lactobacilli themselves, Lactobacillus fermentum showed stronger inhibitory effects than Lactobacillus salivarius. However, the fermentative broth of Lactobacillus fermentum showed weaker inhibitory effects than that of Lactobacillus salivarius. These data suggested that lactobacilli and their fermentative broth exhibit antagonistic growth activity, and consumption of probiotics or their broth containing lactobacilli may benefit oral health.

Antimicrobial activity of pediocin PA-1 against Oenococcus oeni and other wine bacteria

Pediocin PA-1 is an antimicrobial peptide produced by lactic acid bacteria (LAB) that has been sufficiently well characterised to be used in food industry as a biopreservative. Sulphur dioxide is the traditional antimicrobial agent used during the winemaking process to control bacterial growth and wine spoilage. In this study, we describe the effect of pediocin PA-1 alone and in combination with sulphur dioxide and ethanol on the growth of a collection of 53 oenological LAB, 18 acetic acid bacteria and 16 yeast strains; in addition, production of pediocin PA-1 by Pediococcus acidilactici J347-29 in presence of ethanol and grape must is also reported. Inhibitory concentrations (IC) and minimal bactericide concentrations of pediocin PA-1 were determined against LAB, and revealed a bacteriostatic effect. Oenococcus oeni resulted more sensitive to pediocin PA-1 (IC(50) = 19 ng/ml) than the other LAB species (IC(50) = 312 ng/ml). Cooperative inhibitory effects of pediocin PA-1 and either sulphur dioxide or ethanol were observed on LAB growth. Moreover, the pediocin PA-1 producing P. acidilactici strain J347-29 was able to grow and produce the bacteriocin in presence of ethanol (up to 4% ethanol in the fermentation broth) and grape must (up to 80%), which indicated that pediocin PA-1 can be considered as a potential biopreservative in winemaking.

Wine features related to safety and consumer health: an integrated perspective

This review presents a global view of the current situation of the scientific knowledge about aspects of wine with possible repercussions (positive or negative) on consumer health and wine safety. The presence in wine of some potential harmful compounds such as phytosanitary products, trace metal compounds, sulfites, and some toxics of microbial origin, such as ochratoxin A, ethyl carbamate, and biogenic amines, is discussed. The different strategies and alternative methodologies that are being carried out to reduce or to avoid the presence of these substances in wines are also discussed. In recent years much work has focused on establishing the scientific explanations for the positive biological effects of some wine compounds. In this review, we also examine the latest knowledge regarding wine and health, focusing on two types of compounds that have been related to the positive effects of moderate wine consumption, such as phenolic compounds and bioactive peptides.

Assessment of potential probiotic properties of Lactobacillus spp., Lactococcus spp., and Pediococcus spp. strains isolated from kefir

In this study, the metabolic activities (in terms of quantities of the produced lactic acid, hydrogen peroxide, and exopolysaccharides) of 8 strains of Lactobacillus spp., Lactococcus spp., and Pediococcus spp., were determined. Lactic acid levels produced by strains were 8.1 to 17.4 mg/L. The L. acidophilus Z1L strain produced the maximum amount (3.18 μg/mL) of hydrogen peroxide. The exopolysaccharides (EPS) production by the strains was ranged between 173 and 378 mg/L. The susceptibility of 7 different antibiotics against these strains was also tested. All strains were found to be sensitive to ampicillin. The tolerance of the strains to low pH, their resistance to bile salts of strains, and their abilities to autoaggregate and coaggregate with Escherichia coli ATCC 11229 were also evaluated. High EPS-producing strains showed significant autoaggregation and coaggregation ability with test bacteria (P < 0.01). A correlation also was determined between EPS production and acid-bile tolerance (P < 0.05). EPS production possibly affects or is involved in acid-bile tolerance and aggregation of Lactobacillus spp., Lactococcus spp., and Pediococcus spp. strains and supports the potential of L. acidophilus Z1L strain as new probiotic.

beta-Glucanases as a tool for the control of wine spoilage yeasts

In this study, the antimicrobial activity of a commercial beta-glucanase preparation against wine spoilage yeasts such as Cryptococcus albidus, Dekkera bruxellensis, Pichia membranifaciens, Saccharomyces cerevisiae, Zygosaccharomyces bailii, and Zygosaccharomyces bisporus has been evaluated. Yeast species tested showed different sensitivities to the enzyme preparation. In vitro assays in laboratory medium (GPY) showed inhibition by the beta-glucanase preparation of D. bruxellensis and Z. bailii growth with IC(50) and MIC values approximately 3 to 4-fold greater than the recommended dose for improving wine filtration. Wine spoilage experiments showed antimicrobial action against D. bruxellensis and Z. bailii although with reduced effectiveness to that showed in laboratory medium. Under the conditions tested, the addition of beta-glucanase did not affect wine enological parameters. Our data suggest the potential use of beta-glucanases as antimicrobial agents in wine and indicate that the application of antimicrobial enzymes for yeast spoilage control deserves further investigation.

Role of specific components from commercial inactive dry yeast winemaking preparations on the growth of wine lactic acid bacteria

The role of specific components from inactive dry yeast preparations widely used in winemaking on the growth of three representative wine lactic acid bacteria (Oenococcus oeni, Lactobacillus hilgardii and Pediococcus pentosaceus) has been studied. A pressure liquid extraction technique using solvents of different polarity was employed to obtain extracts with different chemical composition from the inactive dry yeast preparations. Each of the extracts was assayed against the three lactic acid bacteria. Important differences in the effect of the extracts on the growth of the bacteria were observed, which depended on the solvent employed during the extraction, on the type of commercial preparations and on the lactic acid bacteria species. The extracts that exhibited the most different activity were chemically characterized in amino acids, free monosaccharides, monosaccharides from polysaccharides, fatty acids and volatile compounds. In general, specific amino acids and monosaccharides were related to a stimulating effect whereas fatty acid composition and likely some volatile compounds seemed to show an inhibitory effect on the growth of the lactic acid bacteria. These results may provide novel and useful information in trying to obtain better and more specific formulations of winemaking inactive dry yeast preparations.

Application of natural antimicrobials for food preservation

In this review, antimicrobials from a range of plant, animal, and microbial sources are reviewed along with their potential applications in food systems. Chemical and biochemical antimicrobial compounds derived from these natural sources and their activity against a range of pathogenic and spoilage microorganisms pertinent to food, together with their effects on food organoleptic properties, are outlined. Factors influencing the antimicrobial activity of such agents are discussed including extraction methods, molecular weight, and agent origin. These issues are considered in conjunction with the latest developments in the quantification of the minimum inhibitory (and noninhibitory) concentration of antimicrobials and/or their components. Natural antimicrobials can be used alone or in combination with other novel preservation technologies to facilitate the replacement of traditional approaches. Research priorities and future trends focusing on the impact of product formulation, intrinsic product parameters, and extrinsic storage parameters on the design of efficient food preservation systems are also presented.

Bacterial spoilage of wine and approaches to minimize it

Bacteria are part of the natural microbial ecosystem of wine and play an important role in winemaking by reducing wine acidity and contributing to aroma and flavour. Conversely, they can cause numerous unwelcome wine spoilage problems, which reduce wine quality and value. Lactic acid bacteria, especially Oenococcus oeni, contribute positively to wine sensory characters, but other species, such as Lactobacillus sp. and Pediococcus sp can produce undesirable volatile compounds. Consequences of bacterial wine spoilage include mousy taint, bitterness, geranium notes, volatile acidity, oily and slimy-texture, and overt buttery characters. Management of wine spoilage bacteria can be as simple as manipulating wine acidity or adding sulfur dioxide. However, to control the more recalcitrant bacteria, several other technologies can be explored including pulsed electric fields, ultrahigh pressure, ultrasound or UV irradiation, and natural products, including bacteriocins and lysozyme.

Selectivity and antimicrobial action of bovine lactoferrin derived peptides against wine lactic acid bacteria

In this study, the antibacterial activities of a bovine Lactoferrin pepsin hydrolysate (LFH) and a synthetic peptide derived from bovine lactoferricin (LfcinB(17-31)) have been evaluated against Oenococcus oeni and three additional lactic acid bacteria (LAB) known to cause spoilage during winemaking processes. Inhibition of bacterial growth was demonstrated in vitro in synthetic broth media (MRS) for both LFH and LfcinB(17-31). The bactericidal activity of the synthetic peptide was also assayed and found to vary depending on the bacterial species and the matrix in which exposure to peptide occurred (either MRS broth or white must). Specificity of LfcinB(17-31) for Lactobacillus brevis, Pediococcus damnosus, and O. oeni was demonstrated in must fermentation experiments in which these three LAB co-existed with the winemaking Saccharomyces cerevisiae T73 in the presence of the peptide. Finally, fermentation experiments also showed that LfcinB(17-31) at inhibitory concentrations did not alter either fermentation kinetics or specific enological parameters.