Purification and characteristics of bifidocin A, a novel bacteriocin produced by Bifidobacterium animals BB04 from centenarians' intestine

Beyond Conventional Meat Preservation: Saddling the Control of Bacteriocin and Lactic Acid Bacteria for Clean Label and Functional Meat Products

Advancements in food science and technology have paved the way for the development of natural antimicrobial compounds to ensure the safety and quality of meat and meat products. Among these compounds, bacteriocin produced by lactic acid bacteria has gained considerable scientific attention for its ability to preserve the healthy properties of meat while preventing spoilage. This natural preservative is seen as a pioneering tool and a potent alternative to chemical preservatives and heat treatment, which can have harmful effects on the nutritional and sensory qualities of meat. Bacteriocin produced by lactic acid bacteria can be used in various forms, including as starter/protective cultures for fermented meats, purified or partially purified forms, loaded in active films/coatings, or established in encapsulate systems. This review delves into the downstream purification schemes of LAB bacteriocin, the elucidation of their characteristics, and their modes of action. Additionally, the application of LAB bacteriocins in meat and meat products is examined in detail. Overall, the use of LAB bacteriocins holds immense potential to inspire innovation in the meat industry, reducing the dependence on harmful chemical additives and minimizing the adverse effects of heat treatment on nutritional and sensory qualities. This review provides a comprehensive understanding of the potential of bacteriocin produced by lactic acid bacteria as a natural and effective meat preservative.

The Genome of Bifidobacterium longum subsp. infantis YLGB-1496 Provides Insights into Its Carbohydrate Utilization and Genetic Stability

Bifidobacterium longum subsp. infantis YLGB-1496 (YLGB-1496) is a probiotic strain isolated from human breast milk. The application of YLGB-1496 is influenced by carbohydrate utilization and genetic stability. This study used genome sequencing and morphology during continuous subculture to determine the carbohydrate utilization characteristics and genetic stability of YLGB-1496. The complete genome sequence of YLGB-1496 consists of 2,758,242 base pairs, 2442 coding sequences, and a GC content of 59.87%. A comparison of carbohydrate transport and metabolism genes of Bifidobacterium longum subsp. infantis (B. infantis) showed that YLGB-1496 was rich in glycosyl hydrolase 13, 20, 25, and 109 gene families. During continuous subculture, the growth characteristics and fermentation activity of the strain were highly stable. The bacterial cell surface and edges of the 1000th-generation strains were progressively smoother and well-defined, with no perforations or breaks in the cell wall. There were 20 SNP loci at the 1000th generation, fulfilling the requirement of belonging to the same strain. The presence of genes associated with cell adhesion and the absence of resistance genes supported the probiotic characteristics of the strain. The data obtained in this study provide insights into broad-spectrum carbohydrate utilization, genomic stability, and probiotic properties of YLGB-1496, which provide theoretical support to promote the use of YLGB-1496.

In Vitro Hypoglycemic Activities of Lactobacilli and Bifidobacterium Strains from Healthy Children's Sources and Their Effect on Stimulating GLP-1 Secretion in STC-1 Cells

A long-term use of chemical drugs cannot cure type II diabetes mellitus (T2DM) and their numerous toxic side effects can be harmful to human health. In recent years, probiotics have emerged as a natural resource to replace chemical drugs in alleviating many human ailments. Healthy children's intestines have a lot of colonized Lactobacilli and Bifidobacterium, and these beneficial bacteria can help promote overall health. The objective of this study was to isolate potential antidiabetic probiotic strains from healthy children and evaluate their application prospects. Firstly, Lactobacillus and Bifidobacterium strains were isolated from healthy children's feces and identified by the pheS or clpC genes with their respective 16S rRNA genes. Then, hydrophobicity, artificial gastrointestinal fluid tolerance, α-Glucosidase and Dipeptidyl peptidase IV (DPP-IV) inhibitory activities of isolated strains were determined, and antioxidant activities and promoting secretion of GLP-1 in STC-1 cells of candidate strains were tested. Results showed that 6 strains of Lactobacillus and Bifidobacterium were obtained from the feces of healthy children aged 3 years, respectively, including Lacticaseibacillus paracasei L-21 and L-25, Levilactobacillus brevis L-16, Lentilactobacillus buchneri L-9, Lactiplantibacillus plantarum L-8 and L-3, Bifidobacterium bifidum 11-1 and B-84, Bifidobacterium longum subsp. longum 6-1, 6-2, B42 and B53. The hydrophobicity and auto-aggregation levels of all these strains were higher than 30% and 50%, respectively, and the decrease in the number of colonies of all strains in the artificial gastrointestinal fluid was less than 2 log CFU/mL. Strains L-3, L-8, L-9, L-21, 6-1, 11-1, B53 and B84 were selected based on their high α-glucosidase inhibitory activity and DPP-IV inhibitory activity, and results of the antioxidant capacity assay showed that the remaining strains all had intense comprehensive antioxidant activity. Additionally, Lacticaseibacillus paracasei L-21 and Bifidobacterium longum subsp. longum B-53 had the most substantial prompting effect on GLP-1 secretion in the STC-1 cell line. These results indicated that Lacticaseibacillus paracasei L-21 and Bifidobacterium longum subsp. longum B-53 could be used as a potential antidiabetic strain; thus, its application as a food supplement and drug ingredient could be recommended after in vivo mitigation of type II diabetes test.

Bifidobacteria in Fermented Dairy Foods: A Health Beneficial Outlook

Bifidobacteria, frequently present in the human gastrointestinal tract, play a crucial role in preserving gut health and are mostly recognized as beneficial probiotic microorganisms. They are associated with fermenting complex carbohydrates, resulting in the production of short-chain fatty acids, bioactive peptides, exopolysaccharides, and vitamins, which provide energy and contribute to gut homeostasis. In light of these findings, research in food processing technologies has harnessed probiotic bacteria such as lactobacilli and bifidobacteria for the formulation of a wide range of fermented dairy products, ensuring their maximum survival and contributing to the development of distinctive quality characteristics and therapeutic benefits. Despite the increased interest in probiotic dairy products, introducing bifidobacteria into the dairy food chain has proved to be complicated. However, survival of Bifidobacterium species is conditioned by strain of bacteria used, metabolic interactions with lactic acid bacteria (LAB), fermentation parameters, and the temperature of storage and preservation of the dairy products. Furthermore, fortification of dairy foods and whey beverages with bifidobacteria have ability to change physicochemical and rheological properties beyond economic value of dairy products. In summary, this review underscores the significance of bifidobacteria as probiotics in diverse fermented dairy foods and accentuates their positive impact on human health. By enhancing our comprehension of the beneficial repercussions associated with the consumption of bifidobacteria-rich products, we aim to encourage individuals to embrace these probiotics as a means of promoting holistic health.

Understanding the role of gut microfloral bifidobacterium in cancer and its potential therapeutic applications

Gut microbiota research has gained a tremendous amount of attention from the scientific community because of its contribution to gut homeostasis, human health, and various pathophysiological conditions. The early colonizer of the human gut, i.e., bifidobacteria, has emerged as an efficient probiotic in various diseased conditions, including cancer. This review explores the pros and cons of Bifidobacterium in various malignancies and various therapeutic strategies. We have illustrated the controversial role of bifidobacteria participating in various malignancies as well as described the current knowledge regarding its use in anticancer therapies. Ultimately, this article also addresses the need for further extensive research in elucidating the mechanism of how bifidobacteria is involved and is indirectly affecting the tumor microenvironment. Exhaustive and large-scale research is also required to solve the controversial questions regarding the involvement of bifidobacteria in cancer research.

Gene expression and molecular characterization of recombinant subtilisin from Bacillus subtilis with antibacterial, antioxidant and anticancer properties

This study investigated the multifunctional attributes such as, antibacterial, antioxidant and anticancer potential of recombinant subtilisin. A codon-optimized subtilisin gene was synthesized from Bacillus subtilis and was successfully transformed into E. coli DH5α cells which was further induced for high level expression in E. coli BL21 (DE3). An affinity purified ~40 kDa recombinant subtilisin was obtained that revealed to be highly alkali-thermostable based on the thermodynamic parameters. The kinetic parameters were deduced that indicated higher affinity of N-Suc-F-A-A-F-pNA substrate towards subtilisin. Recombinant subtilisin demonstrated strong antibacterial activity against several pathogens and showed minimum inhibitory concentration of 0.06 μg/mL against B. licheniformis and also revealed high stability under the influence of several biochemical factors. It also displayed antioxidant potential in a dose dependent manner and exhibited cell cytotoxicity against A549 and MCF-7 cancerous cell lines with IC50 of 5 μM and 12 μM respectively. The identity of recombinant subtilisin was established by MALDI-TOF mass spectrum depicting desired mass peaks and N-terminal sequence as MRSK by MALDI-TOF-MS. The deduced N- terminal amino acid sequence by Edman degradation revealed high sequence similarity with subtilisins from Bacillus strains. The structural and functional analysis of recombinant antibacterial subtilisin was elucidated by Raman, circular dichroism and nuclear magnetic resonance spectroscopy and thermogravimetric analysis. The results contribute to the development of highly efficient subtilisin with enhanced catalytic properties making it a promising candidate for therapeutic applications in healthcare industries.

Bifidobacterium longum subsp. infantis as widespread bacteriocin gene clusters carrier stands out among the Bifidobacterium

Bifidobacterium is the dominant genus, particularly in the intestinal tract niche of healthy breast-fed infants, and many of these strains have been proven to elicit positive effects on infant development. In addition to its effective antimicrobial activity against detrimental microorganisms, it helps to improve the intestinal microbiota balance. The isolation and identification of bacteriocins from Bifidobacterium have been limited since the mid-1980s, leading to an underestimation of its ability for bacteriocin production. Here, we employed a silicon-based search strategy to mine 354 putative bacteriocin gene clusters (BGCs), most of which have never been reported, from the genomes of 759 Bifidobacterium strains distributed across 9 species. Consistent with previous reports, most Bifidobacterium strains did not carry or carry only a single BGC; however, Bifidobacterium longum subsp. infantis, in contrast to other Bifidobacterium species, carried numerous BGCs, including lanthipeptides, lasso peptides, thiopeptides, and class IId bacteriocins. The antimicrobial activity of the crude bacteriocins and transcription analysis confirmed its potential for bacteriocin biosynthesis. Additionally, we investigated the association of bacteriocins with the phylogenetic positions of their homologs from other genera and niches. In conclusion, this study re-examines a few Bifidobacterium species traditionally regarded as a poor source of bacteriocins. These bacteriocin genes impart a competitive advantage to Bifidobacterium in colonizing the infant intestinal tract. IMPORTANCE Development of the human gut microbiota commences from birth, with bifidobacteria being among the first colonizers of the newborn intestinal tract and dominating it for a considerable period. To date, the genetic basis for the successful adaptation of bifidobacteria to this particular niche remains unclear since studies have mainly focused on glycoside hydrolase and adhesion-related genes. Bacteriocins are competitive factors that help producers maintain colonization advantages without destroying the niche balance; however, they have rarely been reported in Bifidobacterium. The advancement in sequencing methods and bacteriocin databases enables the use of a silicon-based search strategy for the comprehensive and rapid re-evaluation of the bacteriocin distribution of Bifidobacterium. Our study revealed that B. infantis carries abundant bacteriocin biosynthetic gene clusters for the first time, presenting new evidence regarding the competitive interactions of Bifidobacterium in the infant intestinal tract.

Purification and characterization of a novel low-molecular-weight antimicrobial peptide produced by Lactiplantibacillus plantarum NMGL2

The present study aimed to purify and characterize a novel low-molecular-weight antimicrobial peptide (AMP) named as PNMGL2 produced by Lactiplantibacillus plantarum NMGL2. The AMP was effectively separated and purified by ethyl acetate extraction and DEAE-Sepharose anion exchange chromatography. Tricine-SDS-PAGE of the purified AMP showed a major protein band below 1.7 kDa, which was identified by MALDI-TOF MS to be a hexapeptide LNFLKK (761.95 Da), and structurally characterized to be combination of helixes and random coil by a PEP-FOLD 3 De novo approach. The antimicrobial activity of LNFLKK was confirmed by chemical synthesis of the peptide that showed clear inhibition (MIC 7.8 mg/mL) against both Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes), and Gram-negative bacteria (Enterobacter sakazakii, Escherichia coli and Shigella flexneri). PNMGL2 was pH resistant (pH 2-9), heat stable (121 °C, 30 min), and protease sensitive. Treatment of UV rays, sodium chloride and organic solvents did not decrease the activity. Sequencing of the whole genome of L. plantarum NMGL2 revealed presence of a bacteriocin gene cluster with two putative bacteriocin genes (ORF4 and ORF5) that were not expressed, confirming the significance of PNMGL2 contributing the antimicrobial activity of the strain. This study demonstrated the low-molecular-weight AMP that was uncharacterized in the relevant available databases, suggesting its potential application as a novel natural food preservative.

Natural Antimicrobials for Listeria monocytogenes in Ready-to-Eat Meats: Current Challenges and Future Prospects

Listeria monocytogenes, an intra-cellular, Gram-positive, pathogenic bacterium, is one of the leading agents of foodborne illnesses. The morbidity of human listeriosis is low, but it has a high mortality rate of approximately 20% to 30%. L. monocytogenes is a psychotropic organism, making it a significant threat to ready-to-eat (RTE) meat product food safety. Listeria contamination is associated with the food processing environment or post-cooking cross-contamination events. The potential use of antimicrobials in packaging can reduce foodborne disease risk and spoilage. Novel antimicrobials can be advantageous for limiting Listeria and improving the shelf life of RTE meat. This review will discuss the Listeria occurrence in RTE meat products and potential natural antimicrobial additives for controlling Listeria.

A novel bacteriocin against multiple foodborne pathogens from Lacticaseibacillus rhamnosus isolated from juice ferments: ATF perfusion-based preparation of viable cells, characterization, antibacterial and antibiofilm activity

Foodborne pathogens and their biofilms pose a risk to human health through food chain. However, the bacteriocin resources combating this threat are still limited. Here, Lacticaseibacillus rhamnosus, one of the most used probiotics in food industry, was prepared on a large scale using alternating tangential flow (ATF) perfusion-based technology. Compared to the conventional fed-batch approach, ATF perfusion remarkably increased the viable cells of L. rhamnosus CLK 101 to 11.93 ± 0.14 log CFU/mL. Based on obtained viable cells, we purified and characterized a novel bacteriocin CLK_01 with a broad spectrum of activity against both Gram-positive and Gram-negative foodborne pathogens. LC-MS/MS analysis revealed that CLK_01 has a molecular mass of 701.49 Da and a hydrophobic amino acid composition of I-K-K-V-T-I. As a novel bacteriocin, CLK_01 showed high thermal stability and acid-base tolerance over 25-121 °C and pH 2-10. It significantly reduced cell viability of bacterial pathogens (p < 0.001), and strongly inhibited their biofilm formation. Scanning electron microscopy demonstrated deformation of pathogenic cells caused by CLK_01, leading to cytoplasmic content leakage and bacterial death. Summarily, we employed ATF perfusion to obtain viable L. rhamnosus, and presented that bacteriocin CLK_01 could serve as a promising biopreservative for controlling foodborne pathogenic bacteria and their biofilms.

Purification, HR-LC-ESI-MS-MS Identification, and Peptide Prediction of Bacteriocin-Like Inhibitory Substances Produced by Streptomyces sp. Isolated from Chanos chanos

Consumption of fresh and minimally processed food is closely related to foodborne diseases. To minimize the adverse effects, bacteriocin-like inhibitory substance (BLIS) as a natural preservative can be used. One of the bacteriocins with promising activity was produced by Streptomyces sp. Using gel filtration chromatography, the bacteriocin purification process succeeded in obtaining semi-purified fractions with broad-spectrum inhibitory activity to foodborne pathogen bacteria. These fractions are also stable up to 100 °C and pH 2.0–7.0. High-Resolution Liquid Chromatography Electrospray Ionization-Tandem Mass Spectrometry analysis followed by orthogonal projection to latent structure showed that each fraction had eight peaks with the highest positive correlation to BLIS-specific activity. Peptide identification based on MS spectrum found 597 predictive peptides, of which 42 predictive peptides with antimicrobial peptide characteristics and the highest iAMPpred antimicrobial peptide probability (>0.5) were selected. The selected predictive peptides have molecular mass of 247.13-615.37 Da and consist of at least 20% hydrophobic amino acids with a hydrophobicity value of 14.72 Kcal mol⁻¹. The results of this study indicate the effectiveness of BLIS purification by gel filtration chromatography and the promising potential of semi-purified BLIS as a natural preservative. Besides, the active peptides in semi-purified BLIS can also be identified quickly so that the isolation process to obtain purified-BLIS can be carried out more efficiently.

Bifidobacterium spp. as functional foods: A review of current status, challenges, and strategies

Members of Bifidobacterium are among the first microbes to colonize the human intestine naturally, their abundance and diversity in the colon are closely related to host health. Recently, the gut microbiota has been gradually proven to be crucial mediators of various metabolic processes between the external environment and the host. Therefore, the health-promoting benefits of Bifidobacterium spp. and their applications in food have gradually been widely concerned. The main purpose of this review is to comprehensively introduce general features, colonization methods, and safety of Bifidobacterium spp. in the human gut, highlighting its health benefits and industrial applications. On this basis, the existing limitations and scope for future research are also discussed. Bifidobacteria have beneficial effects on the host's digestive system, immune system, and nervous system. However, the first prerequisite for functioning is to have enough live bacteria before consumption and successfully colonize the colon after ingestion. At present, strain breeding, optimization (e.g., selecting acid and bile resistant strains, adaptive evolution, high cell density culture), and external protection technology (e.g., microencapsulation and protectants) are the main strategies to address these challenges in food application.

Strategies for Biocontrol of Listeria monocytogenes Using Lactic Acid Bacteria and Their Metabolites in Ready-to-Eat Meat- and Dairy-Ripened Products

Listeria monocytogenes is one of the most important foodborne pathogens. This microorganism is a serious concern in the ready-to-eat (RTE) meat and dairy-ripened products industries. The use of lactic acid bacteria (LAB)-producing anti-L. monocytogenes peptides (bacteriocins) and/or lactic acid and/or other antimicrobial system could be a promising tool to control this pathogen in RTE meat and dairy products. This review provides an up to date about the strategies of use of LAB and their metabolites in RTE meat products and dairy foods by selecting the most appropriate strains, by analysing the mechanism by which they inhibit L. monocytogenes and methods of effective application of LAB, and their metabolites in these kinds of products to control this pathogen throughout the processing and storage. The selection of LAB with anti-L. monocytogenes activity allows to dispose of effective strains in meat and dairy-ripened products, achieving reductions form 2–5 logarithmic cycles of this pathogen throughout the ripening process. The combination of selected LAB strains with antimicrobial compounds, such as acid/sodium lactate and other strategies, as the active packaging could be the next future innovation for eliminating risk of L. monocytogenes in meat and dairy-ripened products.

The Potential Role of Gut Microbiota in Alzheimer’s Disease: from Diagnosis to Treatment

Gut microbiota is emerging as a key regulator of many disease conditions and its dysregulation is implicated in the pathogenesis of several gastrointestinal and extraintestinal disorders. More recently, gut microbiome alterations have been linked to neurodegeneration through the increasingly defined gut microbiota brain axis, opening the possibility for new microbiota-based therapeutic options. Although several studies have been conducted to unravel the possible relationship between Alzheimer’s Disease (AD) pathogenesis and progression, the diagnostic and therapeutic potential of approaches aiming at restoring gut microbiota eubiosis remain to be fully addressed. In this narrative review, we briefly summarize the role of gut microbiota homeostasis in brain health and disease, and we present evidence for its dysregulation in AD patients. Based on these observations, we then discuss how dysbiosis might be exploited as a new diagnostic tool in early and advanced disease stages, and we examine the potential of prebiotics, probiotics, fecal microbiota transplantation, and diets as complementary therapeutic interventions on disease pathogenesis and progression, thus offering new insights into the diagnosis and treatment of this devastating and progressive disease.

Bacteriocins: Properties and potential use as antimicrobials

A variety of bacteriocins originate from lactic acid bacteria, which have recently been modified by scientists. Many strains of lactic acid bacteria related to food groups could produce bacteriocins or antibacterial proteins highly effective against foodborne pathogens such as Staphylococcus aureus, Pseudomonas fluorescens, P. aeruginosa, Salmonella typhi, Shigella flexneri, Listeria monocytogenes, Escherichia coli O157:H7, and Clostridium botulinum. A wide range of bacteria belonging primarily to the genera Bifidobacterium and Lactobacillus have been characterized with different health‐promoting attributes. Extensive studies and in‐depth understanding of these antimicrobials mechanisms of action could enable scientists to determine their production in specific probiotic lactic acid bacteria, as they are potentially crucial for the final preservation of functional foods or for medicinal applications. In this review study, the structure, classification, mode of operation, safety, and antibacterial properties of bacteriocins as well as their effect on foodborne pathogens and antibiotic‐resistant bacteria were extensively studied.

Identification, Characterization, and Antioxidant Potential of Bifidobacterium longum subsp. longum Strains Isolated From Feces of Healthy Infants

Increasing evidence has indicated that oxidative stress is associated with the health of infants. Bifidobacterium, especially B. longum subsp. longum strains, are abundant in the gut microbiota of infants, which may have the potential to ameliorate oxidative damage. Thus, this study aimed to isolate and screen B. longum subsp. longum strains with probiotic characters and antioxidant properties as infants’ dietary supplements. In this study, 24 B. longum subsp. longum strains were isolated from 15 healthy infants identified via 16S rRNA and heat shock protein 60 (hsp60) sequences. B. longum subsp. longum B13, F2, K4, K5, K10, K13, and K15 strains were selected based on high values obtained from autoaggregation, hydrophobicity, and adhesion assays to HT-29 cells. Among these seven strains, B. longum subsp. longum F2, K5, K10, and K15 were selected according to the high tolerance of gastrointestinal tract conditions compared to Bifidobacterium animalis subsp. lactis BB-12. Among these four strains, B. longum subsp. longum K5 was susceptible to common antibiotics and showed the highest intestinal epithelial cell proliferation of CCD 841 CoN. Additionally, B. longum subsp. longum K5 showed a strong antioxidant capacity, and its supernatant exhibited better activity of reducing power, hydroxyl radical scavenging, and DPPH radical scavenging than that of the intact cells with cell-free extracts. The findings indicated that B. longum subsp. longum K5 could be used as a probiotic candidate in infant nutrition.

Controlled Release Study on Bifidocin A from a Polyvinyl Alcohol/Chitosan Blend Particle-Based Biodegradable and Active Packaging Coupled with Mechanistic Assessment and Experimental Modeling

On the basis of PVA-CS, which is incorporated with Bifidocin A, anti-microbial biodegradable films were prepared, characterized by their abilities to control the Bifidocin A's total release rate into foods as needed for packaging of active foods. This study aimed to explore the anti-microbial effects and release kinetics of active substances in polyvinyl alcoholchitosan (PVA-CS) particle composite films added with Bifidocin A. Pseudomonas fluorescens was used as indicator bacteria to evaluate the anti-microbial activity of the films. Fick's law, power law and negative exponential growth model were applied to further study the release kinetics of Bifidocin A. The results revealed that the composite films of PVA and CS had better mechanical properties and anti-microbial activity when the content of Bifidocin A was 50% with 1:1 PVA/CS, but it impairs the structure of the film, which can be resolved by including a suitable amount of grycerol. The anti-microbial was released faster at higher temperature and concentration of Bifidocin A, and the diffusion coeffcients increased significantlywith the increase of temperature and concentration. According to the thermodynamic parameters, the release of Bifidocin A was endothermic and spontaneous. High correlation factors (R² > 0.99) were acquired by fitting the release data of the Bifidocin A with the negative exponential growth model. The potential of Bifidocin A to deliver from the films into the food analog appropriately at low temperatures favored the obtained active films to be applied on food packaging, especially suitable for refrigerated foods.

Establishing novel roles of bifidocin LHA, antibacterial, antibiofilm and immunomodulator against Pseudomonas aeruginosa corneal infection model

Bifidocin LHA, a novel bacteriocin, was extracted from bee honey B. adolescentis and purified. Bifidocin LHA was characterized as a protein in nature, without lipid or carbohydrate moieties, the molecular weight was 16,000 Da protein, heat-stable and active at a wide range of pH values, bactericidal effect, detergent, and solvents did not affect bifidocin activity and can be classified as type II bacteriocin. In vitro, the antibacterial activity of purified bifidocin LHA was significantly higher than crude bifidocin LHA (P < 0.05) against Pseudomonas aeruginosa (P. aeruginosa). The antibiofilm activity of bifidocin LHA was significantly higher than the antibiofilm activity of Amikacin (P < 0.05). In vivo, bifidocin LHA demonstrates a significant decreased in the number of P. aeruginosa in the eye, while complete clearance of P. aeruginosa comparing with the control (P < 0.05) when treating with Bifidobacterium adolescentis and bifidocin LHA together. Bifidobacterium adolescentis and bifidocin LHA treatment together induced substantial elevation of IL10 and IL-12 concentrations (P < 0.01) that helped to prevent damage caused by the inflammatory response. Succeeded to eradicate P. aeruginosa infection improved by histological patterns of the eye tissues. This study indicated Bifidobacterium adolescentis and bifidocin LHA consider as crucial strategies for the practical treatment of eye infection in the future.

The biological activities of postbiotics in gastrointestinal disorders

According to outcomes from clinical studies, an intricate relationship occurs between the beneficial microbiota, gut homeostasis, and the host's health status. Numerous studies have confirmed the health-promoting effects of probiotics, particularly in gastrointestinal diseases. On the other hand, the safety issues regarding the consumption of some probiotics are still a matter of debate, thus to overcome the problems related to the application of live probiotic cells in terms of clinical, technological, and economic aspects, microbial-derived biomolecules (postbiotics) were introducing as a potential alternative agent. Presently scientific literature confirms that the postbiotic components can be used as promising tools for both prevention and treatment strategies in gastrointestinal disorders with less undesirable side-effects, particularly in infants and children. Future head-to-head trials are required to distinguish appropriate strains of parent cells, optimal dosages of postbiotics, and assessment of the cost-effectiveness of postbiotics compared to alternative drugs. This review provides an overview of the concept and safety issues regarding postbiotics, with emphasis on their biological role in the treatment of some important gastrointestinal disorders.

Potential role of probiotic species in ameliorating oxidative stress, effect on liver profile and hormones in male albino rat model

Probiotics are living micro-organism preparations which can vigorously inhibit the probable pathogens colonization in the gut microbial ecology. Current experiment was designed to investigate the efficacy of imported probiotic species compared with the indigenous probiotics species on the oxidative stress, enzymes, and hormones in animal model. Thirty Albino rats were equally divided into three groups with 10 rats ( n = 10) in each group as Control (C), supplemented with imported probiotic species (IP), and supplemented with indigenous probiotics species (InP) for 21 days under controlled environment. The evaluation of treatments was done by testing the serum oxidative stress markers, liver enzymes (Aspartate transaminase and Alanine aminotransferase), lipid profile, and hormonal dynamics including Lutinizing hormone (LH), follicular stimulating hormone (FSH), and growth hormone (GH) in albino male rats. Results revealed that use of indigenous probiotic species significantly ( p < 0.05) reduces the oxidative stress and improves the antioxidant capacity; liver enzymes, total cholesterol, and LDL-Cholesterol were also reduced significantly ( p < 0.05) in InP as compared to IP group. Moreover, results of hormones including LH, FSH, and GH explored that indigenous probiotics have significant ( p < 0.05) potential to improve these hormones as compared to imported probiotics. Although, it could be concluded that InP have beneficial role in preventing the body from oxidative stress as well as in improving the blood parameters but comprehensive studies are required to investigate the detail gut ecology of the indigenous species which will definitely a strong support in preparing a more suitable local probiotic supplement.

Mining, heterologous expression, purification, antibactericidal mechanism, and application of bacteriocins: A review

Bacteriocins are generally considered as low-molecular-weight ribosomal peptides or proteins synthesized by G⁺ and G^- bacteria that inhibit or kill other related or unrelated microorganisms. However, low yield is an important factor restricting the application of bacteriocins. This paper reviews mining methods, heterologous expression in different systems, the purification technologies applied to bacteriocins, and identification methods, as well as the antibacterial mechanism and applications in three different food systems. Bioinformatics improves the efficiency of bacteriocins mining. Bacteriocins can be heterologously expressed in different expression systems (e.g., Escherichia coli, Lactobacillus, and yeast). Ammonium sulfate precipitation, dialysis membrane, pH-mediated cell adsorption/desorption, solvent extraction, macroporous resin column, and chromatography are always used as purification methods for bacteriocins. The bacteriocins are identified through electrophoresis and mass spectrum. Cell envelope (e.g., cell permeabilization and pore formation) and inhibition of gene expression are common antibacterial mechanisms of bacteriocins. Bacteriocins can be added to protect meat products (e.g., beef and sausages), dairy products (e.g., cheese, milk, and yogurt), and vegetables and fruits (e.g., salad, apple juice, and soybean sprouts). The future research directions are also prospected.

Partial purification and characterization of a broad-spectrum bacteriocin produced by a Lactobacillus plantarum zrx03 isolated from infant's feces

Lactobacillus plantarum zrx03 was a bacteriocin-producing strain isolated from infant's feces. The fermentation supernatant produced by this strain could strongly inhibit Escherichia coli JM109 ATCC 67387, Staphylococcus aureus ATCC 25923, and Listeria monocytogenes CICC 21633, in which the diameter of inhibition zone was 12.83 ± 0.62 mm, 15.08 ± 0.31 mm, 6.75 ± 0.20 mm, respectively, compared with lactic acid bacteria N1, N2, M13, M21, M31, and M37. According to amplification of 16S rRNA gene and identification of phylogenetic tree, this strain had a 1,450 bp sequence and 100% identity to the L. plantarum strain. Based on the influence of different protease treatments, such as pepsin, trypsin, papain, and proteinase K on the antimicrobial activity, this antimicrobial substance was considered to be a natural protein. Using bacteriocin produced by this strain as study object of this experiment, it had been extracted from ammonium sulfate precipitation and different organic solvents. The results showed that ethyl acetate was selected as the optimal solution to crude extraction of bacteriocin after comparing ammonium sulfate precipitation method and organic solvent extraction method, such as n-butanol, n-hexane, dichloromethane, trichloromethane, in which the diameter of the inhibition zones was above 28 mm. Results also showed the inhibition spectrum of the obtained bacteriocin had a broad spectrum of inhibition which could inhibit Gram-positive, Gram-negative, yeast. Especially, it could effectively inhibit S. aureus ATCC 25923, Bacillus subtilis CICC 10002, Bacillus anthracis CICC 20443, E. coli JM109 ATCC 67387, and Salmonella CMCC 541, and the zone diameter of inhibition has reached more than 28 mm. Moreover, it had a good thermal stability which antibacterial activity was retained 70.58% after treatment at 121°C for 30 min, and pH-stability was between pH 2.0-9.0. These results suggested bacteriocin produced by L. plantarum zrx03 had potential application prospects in food preservation.

Purification, characterization and mode of action of enterocin, a novel bacteriocin produced by Enterococcus faecium TJUQ1

Enterococcus faecium TJUQ1 with high bacteriocin-producing ability was isolated from pickled Chinese celery. In this study, enterocin TJUQ1 was purified by ammonium sulfate precipitation, reversed-phase chromatography (Sep-Pak C₈) and cation-exchange chromatography. The activity of the purified bacteriocin was 44,566.41 ± 874.69 AU/mg, which corresponds to a purification fold of 35.89 ± 2.34. The molecular mass was 5520 Da by MALDI-TOF MS and Tris-Tricine SDS-PAGE. The result of LC-MS/MS showed that the bacteriocin shared 59.15% identity with enterocin produced by E. faecium GN (accession no. O34071). PCR amplification revealed that E. faecium TJUQ1 possesses a gene encoding enterocin B with 60% identity to enterocin B. Circular dichroism (CD) spectroscopy showed that the molecular conformation was 32.6% helix, 19.5% beta, 12.9% turn and 35.0% random. The stability of enterocin TJUQ1 was measured. After exposure at 121 °C for 15 min, the residual antimicrobial activity of enterocin TJUQ1 was 85.95 ± 1.32%. The antimicrobial activity of enterocin TJUQ1 was still active over a pH range of 3-11. Enterocin TJUQ1 was inactivated after exposure to proteolytic enzymes but was not inactivated by lipase or amylase. These results showed that enterocin TJUQ1 was a novel class II bacteriocin. Enterocin TJUQ1 showed wide antibacterial activity against food-borne gram-negative and gram-positive pathogens, such as Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Salmonella enterica. The MIC was 5.26 ± 0.24 μg/mL against L. monocytogenes CMCC 1595. SEM and TEM were used to observe the changes in the morphological and intracellular organization of L. monocytogenes CMCC 1595 cells treated with enterocin TJUQ1. The results demonstrated that enterocin TJUQ1 increased extracellular electrical conductivity, facilitated pore formation, triggered the release of UV-absorbing materials, ATP and LDH, and even caused cell lysis in L. monocytogenes CMCC 1595 cells. Based on the characterization, the wide inhibitory spectrum and mode of action determined so far, enterocin TJUQ1 is a potential preservative for the food industry.

Health Benefits of Heat-Killed (Tyndallized) Probiotics: An Overview

Nowadays, the oral use of probiotics is widespread. However, the safety profile with the use of live probiotics is still a matter of debate. Main risks include: Cases of systemic infections due to translocation, particularly in vulnerable patients and pediatric populations; acquisition of antibiotic resistance genes; or interference with gut colonization in neonates. To avoid these risks, there is an increasing interest in non-viable microorganisms or microbial cell extracts to be used as probiotics, mainly heat-killed (including tyndallized) probiotic bacteria (lactic acid bacteria and bifidobacteria). Heat-treated probiotic cells, cell-free supernatants, and purified key components are able to confer beneficial effects, mainly immunomodulatory effects, protection against enteropathogens, and maintenance of intestinal barrier integrity. At the clinical level, products containing tyndallized probiotic strains have had a role in gastrointestinal diseases, including bloating and infantile coli-in combination with mucosal protectors-and diarrhea. Heat-inactivated probiotics could also have a role in the management of dermatological or respiratory allergic diseases. The reviewed data indicate that heat-killed bacteria or their fractions or purified components have key probiotic effects, with advantages versus live probiotics (mainly their safety profile), positioning them as interesting strategies for the management of common prevalent conditions in a wide variety of patients´ characteristics.

Effects of Bioactive Packaging Films Incorporated with Bifidocin A on Microbial Reduction and Quality Parameters of Chill-Stored Spanish Mackerel (Scomberomorus niphonius) Fillets

To evaluate the potential of bifidocin A for preservation of fresh Spanish mackerel fillets, the bioactive packaging films incorporated with bifidocin A (1 × minimal inhibition concentration (MIC), 2 × MIC and 4 × MIC) were developed, and their effects on the microbiological and physicochemical properties and sensory profile of mackerel fillets at refrigerated storage were investigated. Results showed that the incorporation of bifidocin A in cellulosic matrix films did not affect the thickness and elongation of the films, but reduced slightly the tension strength. The films incorporated with 2 × MIC and 4 × MIC bifidocin A presented a broad spectrum of activity against most tested bacteria, including some fish-borne specific spoilage bacteria such as Pseudomonas fluorescens, Shewanella putrefaciens, Brochothrix thermosphacta, and Micrococcus luteus, and maintained their 100% activity for 28 days during storage at 4°C. The bioactive packaging films incorporated with bifidocin A could generally suppress the growth of microflora, especially Pseudomonas and Enterobacteriaceae, as well as substantially inhibit the accumulation of total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS) and hypoxanthine, during chilled mackerel fillets storage. Overall, from a microbiological and physicochemical point of view, a much more effective treatment was achieved with 4 × MIC bifidocin A, extending the shelf life to 12 days and maintaining the relatively low TVB-N value (≤13.2 mg/100 g), TBARS value (≤0.45 mg MDA/kg), and K-value (≤32.8%), as well as a relatively high sensory score (≥7.1) during the whole storage. Hence, the bioactive packaging films incorporated with bifidocin A could be a promising hurdle technology and alternative to conventional processes used for improving the safety and quality of chilled mackerel fillets.

Purification of a Bacteriocin-Like Inhibitory Substance Derived from Pediococcus acidilactici Kp10 by an Aqueous Micellar Two-Phase System

Aqueous micellar two-phase system (AMTPS) is an extractive technique of biomolecule, where it is based on the differential partitioning behavior of biomolecule between a micelle-rich and a micelle-poor phase. In this study, an AMTPS composed of a nonionic surfactant, Triton X-100 (TX-100) was used for purifying a bacteriocin-like inhibitory substance (BLIS) derived from Pediococcus acidilactici Kp10. The influences of the surfactant concentration and the effect of additives on the partitioning behavior and activity yield of the BLIS were investigated. The obtained coexistence curves showed that the mixtures of solutions composed of different surfactant concentrations (5-30% w/w) and 50% w/w crude load were able to separate into two phases at temperatures of above 60 °C. The optimum conditions for BLIS partitioning using the TX-100-based AMTPS were: TX-100 concentration of 22.5% w/w, CFCS load of 50% w/w, incubation time of 30 min at 75 °C, and back-extraction using acetone precipitation. This optimal partitioning resulted in an activity yield of 64.3% and a purification factor of 5.8. Moreover, the addition of several additives, such as sorbitol, KCl, dioctyl sulfosuccinate sodium salt, and Coomassie® Brilliant Blue, demonstrated no improvement in the BLIS separation, except for Amberlite® resin XAD-4, where the activity yield was improved to 70.3% but the purification factor was reduced to 2.3. Results from this study have demonstrated the potential and applicability of TX-100-based AMTPS as a primary recovery method for the BLIS from a complex fermentation broth of P. acidilactici Kp10. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2719, 2019.

Purification and Characterization of Plantaricin LPL-1, a Novel Class IIa Bacteriocin Produced by Lactobacillus plantarum LPL-1 Isolated From Fermented Fish

Bacteriocins are ribosomally synthesized peptides or proteins possessing antibacterial activity against foodborne pathogens and spoilage bacteria. A novel bacteriocin, plantaricin LPL-1 was determined as a class IIa bacteriocin according to the YGNGV motif, and producer strain Lactobacillus plantarum LPL-1 was identified based on physio-biochemical characteristics and 16S rDNA sequence. The novel bacteriocin, plantaricin LPL-1 was purified by salt precipitation, cation exchange, gel filtration, and reverse phase high-performance liquid chromatography (RP-HPLC). The molecular mass of plantaricin LPL-1 was 4347.8467 Da by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis and entire amino acid sequence of plantaricin LPL-1 was VIADKYYGNGVSCGKHTCTVDWGEAFSCSVSHLANFGHGKC. Plantaricin LPL-1 possessed the merits of easy degradation by proteases, wide pH stability (2-10), high thermal stability (121°C, 20 min), surfactants stability and bactericidal activity against foodborne spoilage and pathogens bacteria. The mode action and membrane permeabilization of plantaricin was identified. The information of plantaricin LPL-1 indicated that it is not only a novel class IIa bacteriocin, but also a promising natural and safe biologic preservative for the food preservation industry.

Bacteriocinogenic properties of Escherichia coli P2C isolated from pig gastrointestinal tract: purification and characterization of microcin V

The aim of this study was to isolate and investigate the bacteriocinogenic and probiotic potential of new Gram-negative isolates. Of 22 bacterial isolates from pig intestine and chicken crops, ten isolates had demonstrated a good activity, and the most potent five strains were identified as four E. coli and one as Proteus sp. No virulence factors were detected for E. coli strains isolated from pig intestine. The semi-purified microcins proved to be resistant to temperature and pH variation, but sensitive to proteolytic enzymes. Of particular interest, strain E. coli P2C was the most potent, free of virulence genes and sensitive to tested antibiotics. Purification procedure revealed the presence of a single pure peak having a molecular mass of 8733.94 Da and matching microcin V (MccV). The sequence obtained by LC-MS/MS confirmed the presence of MccV. Purified MccV showed a good activity against pathogenic coliforms, especially E. coli O₁K₁H₇ involved in avian colibacillosis. The present study provides evidence that E. coli strains isolated from pig intestine produce microcin-like substances. E. coli P2C is a safe MccV producer that could be a good candidate for its application as novel probiotic strain to protect livestock and enhance growth performance.

Purification and antibacterial mechanism of fish-borne bacteriocin and its application in shrimp (Penaeus vannamei) for inhibiting Vibrio parahaemolyticus

Vibrio parahaemolyticus: is recognized as the main cause of gastroenteritis associated with consumption of seafood. Bacteriocin-producing Lactobacillus plantarum FGC-12 isolated from golden carp intestine had strong antibacterial activity toward V. parahaemolyticus. The fish-borne bacteriocin was purified by a three-step procedure consisting of ethyl acetate extraction, gel filtration chromatography and high performance liquid chromatography. Its molecular weight was estimated at 4.1 kDa using SDS-PAGE. The fish-borne bacteriocin reached the maximum production at stationary phase after 20 h. It was heat-stable (30 min at 121 °C) and remained active at pH range from 3.0 to 5.5, but was sensitive to nutrasin, papain and pepsin. Its minimum inhibitory concentration for V. parahaemolyticus was 6.0 mg/ml. Scanning electron microscopy analysis showed that the fish-borne bacteriocin disrupted cell wall of V. parahaemolyticus. The antibacterial mechanism of the fish-borne bacteriocin against V. parahaemolyticus might be described as action on membrane integrity in terms of the leakage of electrolytes, the losses of Na⁺K⁺-ATPase, AKP and proteins. The addition of the fish-borne bacteriocin to shrimps leaded V. parahaemolyticus to reduce 1.3 log units at 4 °C storage for 6 day. Moreover, a marked decline in total volatile base nitrogen and total viable counts was observed in bacteriocin treated samples than the control. It is clear that this fish-borne bacteriocin has promising potential as biopreservation for the control of V. parahaemolyticus in aquatic products.

Bifidobacteria-Insight into clinical outcomes and mechanisms of its probiotic action

The invasion of pathogens causes a disruption of the gut homeostasis. Innate immune responses and those triggered by endogenous microbiota form the first line of defence in our body. Pathogens often successfully overcome the resistances offered, calling for therapeutic intervention. Conventional strategy involving antibiotics might eradicate pathogens, but often leave the gut uncolonised and susceptible to recurrences. Probiotic supplements are useful alternatives. Bifidobacterium is one of widely studied probiotic genus, effective in restoring gut homeostasis. Mechanisms of probiotic action of bifidobacteria are several, often with strain-specificity. Analysis of streamlined literature reports reveal that although most studies report the probiotic aspect of bifidobacteria, sporadic documented contradictory results exist, challenging its therapeutic application and prompting studies to unambiguously establish the strain-associated probiotic activity and negate adverse effects prior to its clinical administration. Multi-strain/combinatorial therapy possibly relies on a combination of underlying operating mechanisms, each contributing towards enhanced probiotic efficacy, understanding which could help in developing customised formulations against targeted pathogens. Bifidogenic activity is also mediated by surface-associated structural components such as exopolysaccharides, lipoteichoic acids along with metabolites and bifidocins. This highlights scope for developing advanced structural therapeutic strategy which might be pivotal in replacing intact cell probiotics therapy.