Plantaricin MG active against Gram-negative bacteria produced by Lactobacillus plantarum KLDS1.0391 isolated from “Jiaoke”, a traditional fermented cream from China

Bacteriocins sourced from traditional fermented foods for ensuring food safety: the microbial guards

Concerns about food safety have consistently driven the exploration of potent antimicrobials with probiotic origins. Identification of probiotic-derived bacteriocins as robust alternatives to antibiotics has gained traction following the COVID-19 pandemic. Additionally, the global market is witnessing an increasing preference for minimally processed food products free from chemical additives. Another contributing factor to the search for potent antimicrobials is the escalating number of infections caused by antibiotic-resistant bacteria and the need to mitigate the significant damage inflicted on the commensal human microbiota by broad-spectrum antibiotics. As an alternative bio-preservation strategy, there is substantial enthusiasm for the use of bacteriocins or starter cultures producing bacteriocins in preserving a variety of food items. This review specifically focuses on bacteriocins originating from lactic acid bacteria associated with fermented foods and explores their technological applications as nanobiotics. The food-grade antibiotic alternatives, whether utilized independently or in combination with other antimicrobials and administered directly or encapsulated, are anticipated to possess qualities of safety, stability and non-toxicity suitable for application in the food sector. © 2024 Society of Chemical Industry.

Genome-Based Identification and Characterization of Bacteriocins Selectively Inhibiting Staphylococcus aureus in Fermented Sausages

The bacteriocin-producing Lactiplantibacillus plantarum SL47 was isolated from conventional fermented sausages, and the bacteriocin SL47 was purified using ethyl acetate, Sephadex G-25 gel chromatography, and reversed-phase high-performance liquid chromatography (RP-HPLC). Bacteriocin SL47 was identified by HPLC-MS/MS combined with whole-genome sequencing, and the results showed it consisted of plantaricin A, J, K, and N. Further characterization analysis showed that the bacteriocin SL47 was highly thermostable (30 min, 121 °C), pH stable (2-10), sensitive to protease and exhibited broad-spectrum antibacterial ability against Gram-positive and Gram-negative bacteria. The mechanism of action showed that the bacteriocin SL47 increased cell membrane permeability, and 2 × minimum inhibitory concentration (MIC) treatment for 40 min caused apoptosis of Staphylococcus aureus F2. The count of S. aureus in the sausage that was inoculated with L. plantarum SL47 and bacteriocin SL47 decreased by about 64% and 53% of that in the initial stage, respectively. These results indicated the potential of L. plantarum SL47 and bacteriocin SL47 as a bio-preservative in meat products.

Antimicrobial activity of Lactiplantibacillus plantarum against shiga toxin-producing Escherichia coli

AIMS

The aim of the present work was to characterize the Lactiplantibacillus sp. LP5 strain, isolated from pork production, and identify bacteriocin-like inhibitory substances produced by this strain.

METHODS AND RESULTS

In this study, LP5 was identified by species-specific PCR and 16S rRNA sequencing. Additionally, bacterial growth kinetics, antimicrobial activity, the detection of genes related to plantaricin production, and the genetic expression of plantaricins were determined. Lactiplantibacillus sp. LP5 was identified as Lactiplantibacillus plantarum. The well-diffusion test using cell-free supernatants (CFS), neutralized CFS, CFS treated with catalase, and CFS treated with proteinase K showed that inhibitory effects on a Shiga toxin-producing Escherichia coli (STEC) strain were produced by bacteriocins. The PCR technique allowed the detection of genes encoding E/F plantaricins, as well as J/K and whole genome sequencing, and bacteriocin mining analysis allowed us to confirm the presence of these plantaricins.

CONCLUSIONS

We can conclude that the inhibitory effect of L. plantarum LP5 isolated from pigs against the STEC EDL933 strain could be associated with the bacteriocins production and represents a potential use as a probiotic strain.

The Potential of Lactiplantibacillus plantarum ATCC 14917 in the Development of Alginate-Based Gel Formulations with Anti-Staphylococcus aureus Properties

This study aimed to evaluate the potential of lactic acid bacteria (LAB) in developing alginate-based gel formulations to inhibit Staphylococcus aureus. Initially, the antagonistic actions of three lactic acid bacteria (LAB) (Lacticaseibacillus rhamnosus ATCC 10863, Lactiplantibacillus plantarum ATCC 14917, Limosilactobacillus fermentum ATCC 23271) were evaluated against S. aureus ATCC 25923. All tested LAB inhibited S. aureus, but the highest activity was observed for L. plantarum ATCC 14917 (p < 0.05). The antimicrobial effects of L. plantarum ATCC 14917 cell suspensions, sonicate cells extract, and cell-free supernatants (pH 5 or 7) were analyzed using a broth-based assay. The cell suspensions inhibited S. aureus at concentrations ≥ 10%, and these effects were confirmed by a time-kill assay. Alginate-based gels were formulated with cell suspensions, sonicate cells extract, and cell-free supernatant (pH 5). These formulations inhibited S. aureus growth. Based on the results, the alginate gel with cell suspensions at 10% was selected for further characterization. L. plantarum ATCC 14917 survived in the alginate-based gel, especially when stored at 5 °C. At this temperature, the L. plantarum-containing alginate gel was stable, and it was in compliance with microbiological standards. These findings suggest it can be a promising agent for the topical treatment of infections induced by S. aureus.

Characterization and sequencing analysis of pLP2.5-11 and pLP3.0-4 novel cryptic plasmids from Lactiplantibacillus plantarum WP72/27

We sequenced and described two cryptic plasmids from Lactiplantibacillus plantarum strain WP72/27, termed pLP2.5-11 (OP831909) and pLP3.0-4 (OP831910). Nucleotide sequencing gave the sizes of pLP2.5-11 and pLP3.0-4 as 2754 and 3197 base pairs, with G + C contents 38.89% and 40.88% and predicted two and eight putative open reading frames, respectively. The RepA protein of pLP2.5-11 shared a 99% identity with pC30il, pLP1 and pC30il, whereas the RepB protein of pLP3.0-4 shared a 98% identity with pXY3, a member of the rolling-circle replication (RCR) pC194 family. The origin of plasmid replication was predicted to consist of inverted and directed repeat sequences upstream of the Rep genes. Sequence analysis predicted that both pLP2.5-11 and pLP3.0-4 plasmids replicate via a rolling-circle process.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03684-y.

Nanomedicine for drug resistant pathogens and COVID-19 using mushroom nanocomposite inspired with bacteriocin – A Review

Multidrug resistant (MDR) pathogens have become a major global health challenge and have severely threatened the health of society. Current conditions have gotten worse as a result of the COVID-19 pandemic, and infection rates in the future will rise. It is necessary to design, respond effectively, and take action to address these challenges by investigating new avenues. In this regard, the fabrication of metal NPs utilized by various methods, including green synthesis using mushroom, is highly versatile, cost-effective, eco-compatible, and superior. In contrast, biofabrication of metal NPs can be employed as a powerful weapon against MDR pathogens and have immense biomedical applications. In addition, the advancement in nanotechnology has made possible to modify the nanomaterials and enhance their activities. Metal NPs with biomolecules composite to prevents their microbial adhesion and kills the microbial pathogens through biofilm formation. Bacteriocin is an excellent antimicrobial peptide that works well as an augmentation substance to boost the antimicrobial effects. As a result, we concentrate on the creation of new, eco-compatible mycosynthesized metal NPs with bacteriocin nanocomposite via electrostatic, covalent, or non-covalent bindings. The synergistic benefits of metal NPs with bacteriocin to combat MDR pathogens and COVID-19, as well as other biomedical applications, are discussed in this review. Moreover, the importance of the adverse outcome pathway (AOP) in risk analysis of manufactured metal nanocomposite nanomaterial and their future possibilities also discussed.

A novel approach to Lactiplantibacillus plantarum: From probiotic properties to the omics insights

Lactiplantibacillus plantarum (previously known as Lactobacillus plantarum) strains are one of the lactic acid bacteria (LAB) commonly used in fermentation and their probiotic and functional properties along with their health-promoting roles come to the fore. Food-derived L. plantarum strains have shown good resistance and adhesion in the gastrointestinal tract (GI) and excellent antioxidant and antimicrobial properties. Furthermore, many strains of L. plantarum can produce bacteriocins with interesting antimicrobial activity. This probiotic properties of L. plantarum and existing in different niches give a great potential to have beneficial effects on health. It is also has been shown that L. plantarum can regulate the intestinal microbiota composition in a good way. Recently, omics approaches such as metabolomics, secretomics, proteomics, transcriptomics and genomics try to understand the roles and mechanisms of L. plantarum that are related to its functional characteristics. This review provides an overview of the probiotic properties, including the specific interactions between microbiota and host, and omics insights of L. plantarum.

A comparison of mining methods to extract novel bacteriocins from Lactiplantibacillus plantarum NWAFU-BIO-BS29

One of the most important challenges in the field of food safety is producing natural and safe substances that act against pathogens in food. Bacteriocins and antimicrobial peptides (AMPs) have an anti-pathogens effect for both Gram-negative and positive bacteria. The aim of this study was to isolate and characterize safe lactic acid bacteria from traditional Chinese fermented milk that can produce anti-bacterial molecule compounds and does not harm for humans and animals. Lactiplantibacillus plantarum NWAFU-BIO-BS29 was found to be safe, lacking 16 genes for virulence factors, biogenic amine production and antibiotic resistance, and no hemolysis activity was observed. In contrast, it has ability to produce a novel potential bacteriocin of Plantaricin Bio-LP1. Precipitation of bacteriocin by Ethyl-acetate proved to be a suitable method for the extraction the bacteriocin. Whilst, the purification steps were performed as follows: the protein purification system (AKTA-Purifier equipped with HiTrap (gel column)), followed by reversed phase high-performance liquid chromatography (RP-HPLC) equipped with C18 column. In addition, LC-MS-MS and MALDI-TOF were used to identify the peptide sequences and estimate the molecular weight, respectively. Notably, among the eight peptide sequences considered, a couple of sequences have been announced as uncharacterized in protein database (FDYYFFDKK and KEIDDNSIAVK) with a molecular mass less than 1.3 kDa. The MIC was 0.552 mg/ml and exhibited high stability under various temperature, pH, and enzymes conditions. The best activity was found at temperature and pH of 4 °C and 6 °C, respectively, which are the optimal conditions for preservation of most foods. We concluded that, the described method can arouse a growing interest in mining novel bacteriocins. Plantaricin Bio-LP1 is a potentially unique bacteriocin that is effective as a bio-preservative and could make a promising contribution in food and animal feed industries or in the medical field with further clinical studies.

Bacteriocin-Producing Strain Lactiplantibacillus plantarum LP17L/1 Isolated from Traditional Stored Ewe’s Milk Cheese and Its Beneficial Potential

Stored ewe’s milk lump cheese is a local product that can be a source of autochthonous beneficial microbiota, especially lactic acid bacteria. The aim of this study was to show the antimicrobial potential of Lactiplantibacillus plantarum LP17L/1 isolated from stored ewe’s milk lump cheese. Lpb. plantarum LP17L/1 is a non-hemolytic, non-biofilm-forming strain, susceptible to antibiotics. It contains genes for 10 bacteriocins—plantaricins and exerted active bacteriocin with in vitro anti-staphylococcal and anti-listerial effect. It does not produce damaging enzymes, but it produces β-galactosidase. It also sufficiently survives in Balb/c mice without side effects which indicate its safety. Moreover, a reduction in coliforms in mice jejunum was noted. LP17L/1 is supposed to be a promising additive for Slovak local dairy products.

Novel pathways in bacteriocin synthesis by lactic acid bacteria with special reference to ethnic fermented foods

Ethnic fermented foods are known for their unique aroma, flavour, taste, texture and other sensory properties preferred by every ethnic community in this world culturally as parts of their eatables. Some beneficial microorganisms associated with fermented foods have several functional properties and health-promoting benefits. Bacteriocins are the secondary metabolites produced by the microorganisms mostly lactic acid bacteria present in the fermented foods which can act as lantibiotics against the pathogen bacteria. Several studies have been conducted regarding the isolation and characterization of potent strains as well as their association with different types of bacteriocins. Collective information regarding the gene organizations responsible for the potent effect of bacteriocins as lantibiotics, mode of action on pathogen bacterial cells is not yet available. This review focuses on the gene organizations, pathways include for bacteriocin and their mode of action for various classes of bacteriocins produced by lactic acid bacteria in some ethnic fermented foods.

The Influence of Environmental Conditions on the Antagonistic Activity of Lactic Acid Bacteria Isolated from Fermented Meat Products

The aim of this study was to determine the impact of environmental conditions on the antimicrobial properties of 21 lactic acid bacteria strains in the selected indicator bacteria. To assess the antimicrobial activity of the whole bacteria culture (WBC), the agar well diffusion method was used. The interference of LAB strains with the growth of the selected indicator bacteria was evaluated by incubating co-cultures in the food matrix. Based on the conducted research, it was found that environmental conditions have a significant impact on the antimicrobial activity of lactic acid bacteria strains. The highest antimicrobial activity was recorded under optimal conditions for the development of LAB, the incubation time being different depending on the indicator strain used. The tested LAB strains were characterized by a high ability to inhibit indicator strains, especially in the food matrix. These results led us to further characterize and purify the antimicrobial compound produced by lactic acid bacteria taking into account changing environmental conditions.

The impact of the gut microbiome on toxigenic bacteria

Millions of symbiotic and pathogenic microorganisms known as microbiota colonize the host body. The microbiome plays an important role in human health and colonizes hundreds of different species of multicellular organisms so that they are introduced as the metaorganisms. Changes in the microbial population of the gut microbiome may cause resistance to pathogenic bacteria-induced infection. Understanding the principles of Host-Microbiota Interactions (HMIs) is important because it clarifies our insight towards the mechanisms of infections established in the host. Interactions between the host and the microbiota help answer the question of how a microorganism can contribute to the health or disease of the host. Microbiota can increase host resistance to colonization of pathogenic species. Studying the HMIs network can in several ways delineate the pathogenic mechanisms of pathogens and thereby help to increase useful and novel therapeutic pathways. For example, the potentially unique microbial effects that target the distinct host or interfere with the endogenous host interactions can be identified. In addition, the way mutations in essential proteins in the host and/or in the microbes can influence the interactions between them may be determined. Furthermore, HMIs help in identifying host cell regulatory modules.

Bacteriocins: Recent advances in application as an antimicrobial alternative

Due to the emergence and development of antibiotic resistance in the treatment of bacterial infections, efforts to discover new antimicrobial agents have increased. One of these antimicrobial agents is a compound produced by a large number of bacteria called bacteriocin. Bacteriocins are small ribosomal polypeptides that can exert their antibacterial effects against bacteria close to their producer strain or even non-closely strains. Adequate knowledge of the structure and functional mechanisms of bacteriocins and their spectrum of activity, as well as knowledge of the mechanisms of possible resistance to these compounds will lead to further development of their use as an alternative to antibiotics. Furthermore, most bacteria that live in the gastrointestinal tract (GIT) have the ability to produce bacteriocins, which spread throughout the GIT. Despite antimicrobial studies in vitro, our knowledge of bacteriocins in the GIT and the migration of these bacteriocins from the epithelial barrier is low. Hence, in this study, we reviewed general information about bacteriocins, such as classification, mechanism of action and resistance, emphasizing their presence, stability, and spectrum of activity in the GIT.

Purification, molecular characterization of Lactocin 63 produced by Lactobacillus coryniformis FZU63 and its antimicrobial mode of action against Shewanella putrefaciens

Bacteriocins derived from lactic acid bacteria (LAB) are well recognized as promising food preservative due to high safety and potent antibacterial activity against foodborne pathogens and spoilage bacteria. In this study, an antimicrobial agent-producing strain FZU63 from Chinese sauerkraut was identified as Lactobacillus coryniformis based on physio-biochemical characterization and 16S rDNA sequence analysis. In addition, a bacteriocin was purified from the culture supernatant of L. coryniformis FZU63, and its molecular mass was determined as 1493.709 Da. Moreover, the amino acid sequence of the bacteriocin was predicted to be RQQPMTLDYRW-NH₂ using nanoliter/microliter liquid chromatography combined with triple quadrupole-linear ion trap tandem mass spectrometry and was named as Lactocin 63. Furthermore, Lactocin 63 displays potent antimicrobial activity against the tested Gram-positive and negative bacteria based on the results of determining MICs. Subsequently, the action mode of Lactocin 63 against Shewanella putrefaciens was investigated. The results demonstrated that Lactocin 63 targets and is adsorbed onto the bacterial cell wall and membrane and then disrupts cytoplasmic membrane, which is leading to leakage of cytoplasm according to the results of flow cytometry analysis and the observation of cellular ultra-structure using confocal laser microscopy and atomic force microscopy. Collectively, these results are helpful and providing the theoretical base for developing and applying LAB-derived bacteriocins as promising bio-preservatives to combat foodborne pathogens and spoilage bacteria in seafood industries.Key points• A bacteriocin-producing strain Lactobacillus coryniformis was isolated.• A novel bacteriocin produced by Lactobacillus coryniformis FZU63 was characterized.• Action mechanism of the bacteriocin against S. putrefaciens was elucidated in vitro.

Acetate and auto-inducing peptide are independent triggers of quorum sensing in Lactobacillus plantarum

The synthesis of plantaricin in Lactobacillus plantarum is regulated by quorum sensing. However, the nature of the extra-cytoplasmic (EC) sensing domain of the histidine kinase (PlnB1) and the ability to recognize the auto-inducing peptide PlnA1 is not known. We demonstrate the key motif Ile-Ser-Met-Leu of auto-inducing peptide PlnA1 binds to the hydrophobic region Phe-Ala-Ser-Gln-Phe of EC loop 2 of PlnB1 via hydrophobic interactions and hydrogen bonding. Moreover, we identify a new inducer, acetate, that regulates the synthesis of plantaricin by binding to a positively charged region (Arg-Arg-Tyr-Ser-His-Lys) in loop 4 of PlnB1 via electrostatic interaction. The side chain of Phe143 on loop 4 determined the specificity and affinity of PlnB1 to recognize acetate. PlnA1 activates quorum sensing in log phase growth and acetate in stationary phase to maintain the synthesis of plantaricin under conditions of reduced growth. Acetate activation of PlnB was also evident in four types of PlnB present in different Lb. plantarum strains. Finally, we proposed a model to explain the developmental regulation of plantaricin synthesis by PlnA and acetate. These results have potential applications in improving food fermentation and bacteriocin production.

Health-Promoting Role of Lactiplantibacillus plantarum Isolated from Fermented Foods

Fermentation processes have been used for centuries for food production and preservation. Besides the contribution of fermentation to food quality, recently, scientific interest in the beneficial nature of fermented foods as a reservoir of probiotic candidates is increasing. Fermented food microbes are gaining attention for their health-promoting potential and for being genetically related to human probiotic bacteria. Among them, Lactiplantibacillus (Lpb.) plantarum strains, with a long history in the food industry as starter cultures in the production of a wide variety of fermented foods, are being investigated for their beneficial properties which are similar to those of probiotic strains, and they are also applied in clinical interventions. Food-associated Lpb. plantarum showed a good adaptation and adhesion ability in the gastro-intestinal tract and the potential to affect host health through various beneficial activities, e.g., antimicrobial, antioxidative, antigenotoxic, anti-inflammatory and immunomodulatory, in several in vitro and in vivo studies. This review provides an overview of fermented-associated Lpb. plantarum health benefits with evidence from clinical studies. Probiotic criteria that fermented-associated microbes need to fulfil are also reported.

Enhancement of the antibacterial potential of plantaricin by incorporation into silver nanoparticles

Background

Bacteriocins are proteinaceous compounds produced from lactic acid bacteria. Bacteriocins are well-known for their antibacterial potential and safety for application in food. However, the commercial availability of bacteriocin is facing several limitations; among them is the low yield and short stability period. That calls for a new strategy for overcoming these hurdles. Among these approaches is incorporating bacteriocin in nanoparticles. So, the aim of this study was to enhance the plantaricin produced from isolated Lactobacillus plantarum strain using nanotechnology.

Results

In this study, the plnEF genes encoding plantaricin EF have been identified and sequenced (accession number of MN172264.1). The extracted bacteriocin (EX-PL) was obtained by the ammonium sulfate method. Then, it was used for biosynthesizing plantaricin-incorporated silver nanoparticles (PL-SNPs). The synthesized nanoparticles were confirmed by SEM-EDAX analysis. The antibacterial activity of both combined (PL-SNPs) and extracted plantaricin (EX-PL) were tested against some strains of foodborne pathogenic bacteria. The results revealed that the antibacterial activities were increased by 99.2% on the combination of bacteriocin with the silver nanoparticle. The MIC of EX-PL (7.6 mg/mL) has been lowered after incorporating into silver nanoparticles and reached 0.004 mg/mL for PL-SNPs. Despite that extracted plantaricin showed no inhibitory activity towards Listeria monocytogenes, plantaricin-incorporated silver nanoparticles displayed inhibitory activity against this strain. Furthermore, the stability period at 4 °C was increased from 5 days to 60 days for EX-PL and PL-SNPs, respectively.

Conclusions

Plantaricin-incorporated silver nanoparticles possess higher antibacterial activity and more stability than the free one, which makes it more fitting for combating foodborne pathogens and open more fields for applications in both food and pharmaceutical industries.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-020-00093-z.

Evaluation of the Antibacterial Activity and Probiotic Potential of Lactobacillus plantarum Isolated from Chinese Homemade Pickles

This study investigated the antipathogenic activity and probiotic potential of indigenous lactic acid bacteria (LAB) isolated from Chinese homemade pickles. In total, 27 samples were collected from different sites in China. Fifty-nine yielded pure colonies were identified by 16S rRNA gene sequencing as LAB and were initially evaluated for the antibacterial activity in vitro. Initial screening yielded Lactobacillus plantarum GS083, GS086, and GS090, which showed a broad-spectrum antibacterial activity against food-borne pathogens, especially multidrug-resistant pathogens. Meanwhile, organic acids were mainly responsible for the antimicrobial activity of the LAB strains, and the most abundant of these was lactic acid (19.32 ± 0.95 to 24.79 ± 0.40 g/l). Additionally, three L. plantarum strains demonstrated several basic probiotic characteristics including cell surface hydrophobicity, autoaggregation, and survival under gastrointestinal (GI) tract conditions. The safety of these isolates was also evaluated based on their antibiotic susceptibility, hemolytic risk, bile salt hydrolase activity, and existence of virulence or antibiotic resistance genes. All strains were safe at both the genomic and phenotypic levels. Therefore, L. plantarum GS083, GS086, and GS090 are fairly promising probiotic candidates and may be favorable for use as preservatives in the food industry.

Microbial diversity analysis of jiaoke from Xilingol, Inner Mongolia

Jiaoke is a traditional Mongolian fermented dairy product that is nutritious and has a unique taste. It is made from the fat separated from fermented milk. In this study, we collected 24 jiaoke samples from the Xilingol region of Inner Mongolia. The microbiota composition of the collected samples was analyzed using 16S rRNA small-molecule real-time sequencing, and the lactic acid bacteria (LAB) population was enumerated and isolated by laboratory culture techniques. We used an electronic tongue device to assess the taste quality of the products. One hundred fifty LAB isolates (5 genera and 14 species) were recovered and identified by 16S rRNA sequencing across all samples. Lactococcus lactis and Lactobacillus plantarum accounted for 51.33% and 10.67% of the total isolates, respectively. The small-molecule real-time sequencing of full-length 16S rRNAs revealed an overall bacterial microbiota composition of 10 phyla, 121 genera, and 186 species, largely represented by sequences of Lactococcus (68.46%) and Lactococcus lactis (52.92%) at the genus and species levels, respectively. The electronic tongue analysis revealed that the sweetness, bitterness, sourness, and saltiness of jiaoke varied greatly between samples. The presence of Lactococcus lactis correlated positively with bitter aftertaste; the presence of Lactococcus piscium correlated positively with umami and negatively with astringent and bitter aftertastes; and the presence of Lactobacillus helveticus correlated positively with sourness and negatively with other taste qualities. These results suggest that the microbiota composition and product taste are closely related. The novel LAB strains collected in this work represent valuable natural microbial resources.

Design and preparation of antimicrobial meat wrapping nanopaper with bacterial cellulose and postbiotics of lactic acid bacteria

Lyophilized postbiotics of Lactobacillus plantarum was prepared and impregnated in bacterial nanocellulose (BNC) by ex-situ method to develop an antimicrobial ground meat wrapping nanopaper. The postbiotics incorporated BNC (P-BNC) films were optimized by response surface methodology and their antimicrobial activity against Listeria monocytogenes were examined. The BNC with postbiotics at 21.21% concentration and 28 min impregnation time was chosen as an optimized P-BNC film. The FTIR results confirmed the immobilization of postbiotics in BNC. The P-BNC film represented a significant reduction (~5 log cycles) in L.monocytogenes counts in ground meat at the end of the storage period (9 days at 4 °C). Meat wrapped by P-BNC film displayed a significant decrease in total mesophilic and psychrophiles count and TBA values than the controls. BNC can be considered as a proper carrier for development of antimicrobial film using postbiotics of LAB for food application.

Characterization of a broad spectrum bacteriocin produced by Lactobacillus plantarum MXG-68 from Inner Mongolia traditional fermented koumiss

An agar well diffusion assay (AWDA) was used to isolate a high bacteriocin-producing strain with a broad spectrum of antibacterial activity, strain MXG-68, from Inner Mongolia traditional fermented koumiss. Lactobacillus plantarum MXG-68 was identified by morphological, biochemical, and physiological characteristics and 16S rDNA analysis. The production of antibacterial substance followed a growth-interrelated model, starting at the late lag phase of 4 h and arriving at a maximum value in the middle of the stationary phase at 24 h. Antibacterial activity was abolished or decreased in the presence of pepsin, chymotrypsin, trypsin, proteinase, and papain K. The results showed that antibacterial substances produced by L. plantarum MXG-68 were proteinaceous and could thus be classified as the bacteriocin, named plantaricin MXG-68. The molar mass of plantaricin MXG-68 was estimated to be 6.5 kDa, and the amino acid sequence of its N-terminal was determined to be VYGPAGIFNT. The mode of plantaricin MXG-68 action was determined to be bactericidal. Bacteriocin in cell-free supernatant (CFS) at pH 7 was stable at different temperatures (60 °C, 80 °C, 100 °C, 121 °C for 30 min; 4 °C and - 20 °C for 30 days), as well as at pH 2.0-10.0. Antibacterial activity maintained stable after treatment with organic solvents, surfactants, and detergents but increased in response to EDTA. Response surface methodology (RSM) revealed the optimum conditions of bacteriocin production in L. plantarum MXG-68, and the bacteriocin production in medium optimized by RSM was 26.10% higher than that in the basal MRS medium.

Effects of oligosaccharides on the fermentation properties of Lactobacillus plantarum

In the present work, we studied the effects of different oligosaccharides on Lactobacillus plantarum ATCC14917, focusing on growth and adhesion characteristics and fermented milk flavor. The results showed that mannan-oligosaccharide (MOS) had the greatest proliferative effect on L. plantarum ATCC14917 in vitro. In terms of adhesive properties, the autoaggregation rate of L. plantarum cultured in MOS was 23.76%, adhesion to mucin was 24.65%, and adhesion to Caco-2 cells was 14.71%. These results for L. plantarum cultured with MOS were higher than those for L. plantarum cultured in fructo-oligosaccharides (FOS) or galacto-oligosaccharides (GOS). Furthermore, the surface consistency and viscosity scores of fermented milk of the MOS group was higher than that of milks cultured with FOS or GOS, although MOS had the lowest scores for fermented milk flavor.

Detoxification of Aflatoxin B1 by Antifungal Compounds from Lactobacillus brevis and Lactobacillus paracasei, Isolated from Dairy Products

Aflatoxins are a large group of highly toxic, mutagenic, and carcinogenic mycotoxins produced by specific species of fungi. Potential contamination of food commodities by these compounds causes extensive damage that lead to great economic losses. This study explored the potential use of antifungal compounds, produced by Lactobacillus brevis and Lactobacillus paracasei, for growth inhibition and subsequent aflatoxin B1 production from select strains of Aspergillus flavus and Aspergillus parasiticus. Lactobacilli strains were isolated from traditional Egyptian dairy products, whereas fungal strains were isolated from infected cereal seeds. There were noticeable decreases in mycelium biomass and aflatoxin production as well. L. brevis exhibited the highest reduction of aflatoxin B1 production by A. flavus and A. parasiticus, 96.31 and 90.43%, respectively. The concentrations of amino acids of the antifungal compound produced by L. brevis were significantly higher than that produced by L. paracasei. Asparagine, glutamine, glycine, alanine, and leucine were the most concentrated amino acids for both strains. The antifungal compounds produced by L. brevis and L. paracasei were active in a wide range of pH, heat stable and inactivated by proteolytic enzymes (protease K and trypsin A). The expression of Omt-A gene that involved in the later step of aflatoxin production was evaluated by real-time PCR. There was a vigorous reduction at transcriptional level of Omt-A gene observed in A. flavus that is treated by L. brevis and L. paracasei (80 and 70%, respectively). However, the reduction of Omt-A gene observed in A. parasiticus that is treated by L. brevis and L. paracasei was 64.5 and 52%, respectively. Treating maize seeds with antifungal compounds exhibited great efficiency in controlling fungal infection and increasing seed germination. The results confirmed that lactic acid bacteria are a promising strategy to control food contamination of fermented food and dairy products.

Purification and Characterization of Plantaricin ZJ316, a Novel Bacteriocin against Listeria monocytogenes from Lactobacillus plantarum ZJ316

Bacteriocins are known to be natural preservatives, which are becoming increasingly necessary in many types of food to control the proliferation of pathogenic bacteria. In this study, a novel bacteriocin produced by Lactobacillus plantarum ZJ316, called plantaricin ZJ316, was purified by ammonium sulfate precipitation, gel chromatography, and high-performance liquid chromatography. By mass spectrometry, the molecular mass of plantaricin ZJ316 was determined to be 2,366.06 Da. No homologous sequences were found in databases based on comparisons with the N-terminal amino acid sequencing. The bacteriocin was heat resistant and stable after incubation at pH 2.0 to 10.0. It was sensitive to α-chymotrypsin, trypsin, and proteinase K. Plantaricin ZJ316 had a broad inhibitory activity against gram-negative and gram-positive bacteria, especially Listeria monocytogenes. Our results suggested that this bacteriocin has the potential to inhibit pathogenic bacteria in food products.

Antimicrobial Activity of a Bacteriocin Produced by Enterococcus faecalis KT11 against Some Pathogens and Antibiotic-Resistant Bacteria

In this study, the antimicrobial activity of a bacteriocin produced by Enterococcus faecalis KT11, isolated from traditional Kargı Tulum cheese, was determined, and bacteriocin KT11 was partially characterized. The results showed that bacteriocin KT11 was antagonistically effective against various Gram-positive and Gram-negative test bacteria, including vancomycin- and/or methicillin-resistant bacteria. The activity of bacteriocin KT11 was completely abolished after treatment with proteolytic enzymes (proteinase K, α-chymotrypsin, protease and trypsin), which demonstrates the proteinaceous nature of this bacteriocin. Additionally, bacteriocin KT11 remained stable at pH values ranging from 2 to 11 and after autoclaving at 121℃ for 30 min. In addition, the activity of bacteriocin KT11 was stable after treatment with several surfactants (EDTA, SDS, Triton X-100, Tween 80 and urea) and organic solvents (chloroform, propanol, methanol, ethyl alcohol, acetone, hexane and ethyl ether). Cell-free supernatant of E. faecalis KT11 was subjected to ammonium sulfate precipitation and then desalted by using a 3.5-kDa cut-off dialysis membrane. The bacteriocin activity was determined to be 711 AU/mL in the dialysate. After tricine-SDS-PAGE analysis, one peptide band, which had a molecular weight of ~3.5 kDa, exhibited antimicrobial activity. Because the bacteriocin KT11, isolated from E. faecalis KT11, exhibits a broad antimicrobial spectrum, heat stability and stability over a wide pH range, this bacteriocin can be used as a potential bio-preservative in foods. Additionally, bacteriocin KT11 alone or in combination with conventional antibiotics may provide a therapeutic option for the treatment of multidrug-resistant clinical pathogens after further in vivo studies.

Identification and in vitro assessment of potential probiotic characteristics and antibacterial effects of Lactobacillus plantarum subsp. plantarum SKI19, a bacteriocinogenic strain isolated from Thai fermented pork sausage

A total of 2257 lactic acid bacteria were preliminarily screened for antagonistic activity against Lactobacillus sakei subsp. sakei JCM 1157. Strain SKI19 was selected and identified at the subspecies level as Lactobacillus plantarum subsp. plantarum SKI19, using 16S rRNA gene sequence analysis combined with recA and dnaK genes' amplification. Antibacterial activity of SKI19 was completely lost after treatment of neutralized cell free culture supernatant with proteolytic enzymes, suggesting that SKI19 produced a bacteriocin-like substance that inhibited not only closely related species, but was also effective against Listeria monocytogenes DMST 17303. Viewed under scanning electron microscope, cell membranes of the indicator strain appeared to collapse after exposure to the bacteriocin-like substance. In vitro tests concerning probiotic properties, SKI19 survived under simulated gastrointestinal tract conditions, and adhesion of its cell surface to xylene and chloroform was 90.14 and 89.85%, respectively. Complete inhibition by SKI19 against pathogenic bacteria (Escherichia coli DMST 4212, L. monocytogenes DMST 17303, and Staphylococcus aureus DMST 8840) was observed in co-cultivation under anaerobic conditions. A safety assessment showed that SKI19 was susceptible to several antibiotics and had no haemolytic activity. PCR amplification of virulence factors with the specific primers for ace, asa1, cylLS , efaAfs , hyl, and gelE genes were negative for SKI19. Also, SKI19 did not harbor any hdc, tdc, odc or ldc genes involved in biogenic amine production. The results reveal that SKI19 has probiotic potential and antibacterial activity, and is safe for further application in certain food products.

Role of luxS in Stress Tolerance and Adhesion Ability in Lactobacillus plantarum KLDS1.0391

Lactobacillus plantarum, a probiotic, has a high survival rate and high colonization ability in the gastrointestinal tract. Tolerance to the gastrointestinal environment and adhesion to intestinal epithelial cells by some Lactobacillus species (excluding L. plantarum) are related to luxS/AI-2. Here, the role of luxS in tolerance to simulated digestive juice (SDJ) and adhesion to Caco-2 cells by L. plantarum KLDS1.0391 (hereafter, KLDS1.0391) was investigated. The KLDS1.0391 luxS mutant strain was constructed by homologous recombination. When luxS was deleted, acid and bile salt tolerance and survival rates in SDJ significantly decreased (p < 0.05 for all). The ability of the luxS deletion strain to adhere to Caco-2 cells was markedly lower than that of the wild-type strain (p < 0.05). The ability of the luxS mutant strain to adhere (competition, exclusion, and displacement) to Escherichia coli ATCC 25922 was significantly lower than that of the wild-type strain (p < 0.05 for all). A significant decrease was noted only in the exclusion adhesion inhibition of the luxS mutant strain to Salmonella typhimurium ATCC 14028 (p < 0.05). These results indicate that the luxS gene plays an important role in the gastrointestinal environment tolerance and adhesion ability of KLDS1.0391.

Role of the luxS gene in bacteriocin biosynthesis by Lactobacillus plantarum KLDS1.0391: A proteomic analysis

Certain probiotic species of lactic acid bacteria, especially Lactobacillus plantarum, regulate bacteriocin synthesis through quorum sensing (QS) systems. In this study, we aimed to investigate the luxS-mediated molecular mechanisms of QS during bacteriocin synthesis by L. plantarum KLDS1.0391. In the absence of luxS, the ‘spot-on-the-lawn’ method showed that the bacteriocin production by L. plantarum KLDS1.0391 significantly decreased upon co-cultivation with L. helveticus KLDS1.9207 (P < 0.01) but did not change significantly when mono-cultivated. Furthermore, liquid chromatography-electrospray ionization tandem mass spectrometry analysis showed that, as a response to luxS deletion, L. plantarum KLDS1.0391 altered the expression level of proteins involved in carbohydrate metabolism, amino acid metabolism, fatty acid synthesis and metabolism, and the two-component regulatory system. In particular, the sensor histidine kinase AgrC (from the two-component system, LytTR family) was expressed differently between the luxS mutant and the wild-type strain during co-cultivation, whereas no significant differences in proteins related to bacteriocin biosynthesis were found upon mono-cultivation. In summary, we found that the production of bacteriocin was regulated by carbohydrate metabolism, amino acid metabolism, fatty acid synthesis and metabolism, and the two-component regulatory system. Furthermore, our results demonstrate the role of luxS-mediated molecular mechanisms in bacteriocin production.

Complete genome sequence of bacteriocin-producing Lactobacillus plantarum KLDS1.0391, a probiotic strain with gastrointestinal tract resistance and adhesion to the intestinal epithelial cells

Lactobacillus plantarum KLDS1.0391 is a probiotic strain isolated from the traditional fermented dairy products and identified to produce bacteriocin against Gram-positive and Gram-negative bacteria. Previous studies showed that the strain has a high resistance to gastrointestinal stress and has a high adhesion ability to the intestinal epithelial cells (Caco-2). We reported the entire genome sequence of this strain, which contains a circular 2,886,607-bp chromosome and three circular plasmids. Genes, which are related to the biosynthesis of bacteriocins, the stress resistance to gastrointestinal tract environment and adhesive performance, were identified. Whole genome sequence of Lactobacillus plantarum KLDS1.0391 will be helpful for its applications in food industry.

Comparison of Antibacterial Activity of Lactobacillus plantarum Strains Isolated from Two Different Kinds of Regional Cheeses from Poland: Oscypek and Korycinski Cheese

Oscypek and korycinski are traditional Polish cheeses, exclusively produced in Tatra and in Podlasie region, respectively, produced from raw, unpasteurized milk. The 29 Lactobacillus plantarum strains were isolated on MRS agar from 12 cheese samples and used as a material for study. The main purpose of the work was to assess the antimicrobial properties and recognition of selected strains for the unique antagonistic activity and preservation role in food. It has been found that the highest antimicrobial activity was observed in the case of L. monocytogenes strains; however, the level of that activity was different depending on the Lb. plantarum strain. Strains from oscypek produced broad spectrum, and a few strains isolated from korycinski cheese produced a narrow spectrum of antimicrobial compounds, other than organic acids and hydrogen peroxide. Moreover, the antagonistic activity shown by Lb. plantarum strains is connected with the source from which a given strain was isolated. Strains isolated from oscypek cheese represented stronger activity against L. monocytogenes, whereas strains isolated from korycinski cheese were more active against E. coli. Strains Lb. plantarum Os13 and Kor14 could be considered as good candidates for protective cultures to extend durability of food products.

Purification and Characterization of Plantaricin JLA-9: A Novel Bacteriocin against Bacillus spp. Produced by Lactobacillus plantarum JLA-9 from Suan-Tsai, a Traditional Chinese Fermented Cabbage

Bacteriocins are ribosomally synthesized peptides with antimicrobial activity produced by numerous bacteria. A novel bacteriocin-producing strain, Lactobacillus plantarum JLA-9, isolated from Suan-Tsai, a traditional Chinese fermented cabbage, was screened and identified by its physiobiochemical characteristics and 16S rDNA sequence analysis. A new bacteriocin, designated plantaricin JLA-9, was purified using butanol extraction, gel filtration, and reverse-phase high-performance liquid chromatography. The molecular mass of plantaricin JLA-9 was shown to be 1044 Da by MALDI-TOF-MS analyses. The amino acid sequence of plantaricin JLA-9 was predicted to be FWQKMSFA by MALDI-TOF-MS/MS, which was confirmed by Edman degradation. This bacteriocin exhibited broad-spectrum antibacterial activity against Gram-positive and Gram-negative bacteria, especially Bacillus spp., high thermal stability (20 min, 121 °C), and narrow pH stability (pH 2.0-7.0). It was sensitive to α-chymotrypsin, pepsin, alkaline protease, and papain. The mode of action of this bacteriocin responsible for outgrowth inhibition of Bacillus cereus spores was studied. Plantaricin JLA-9 had no detectable effects on germination initiation over 1 h on monitoring the hydration, heat resistance, and 2,6-pyridinedicarboxylic acid (DPA) release of spores. Rather, germination initiation is a prerequisite for the action of plantaricin JLA-9. Plantaricin JLA-9 inhibited growth by preventing the establishment of oxidative metabolism and disrupting membrane integrity in germinating spores within 2 h. The results suggest that plantaricin JLA-9 has potential applications in the control of Bacillus spp. in the food industry.