Search Results (45)

Escherichia coli O157:H7 is a pathogenic bacterium that causes severe intestinal infections characterized by inflammation and disruption of the intestinal barrier. Probiotic lactic acid bacteria (LAB) from milk can support intestinal health and combat enteric pathogens; however, the potential of feline milk-derived LAB against E. coli O157:H7 infection remains unclear. In this study, Pediococcus acidilactici (P. acidilactici) M22, isolated from feline milk, was evaluated for probiotic activity in vitro and in vivo in a C57BL/6 mouse model of Escherichia coli O157:H7 infection. In vitro assays demonstrated that M22 significantly inhibited the adhesion of Escherichia coli O157:H7 to intestinal epithelial cells. For in vivo assessment, C57BL/6 mice were orally administered M22 prior to infection with E. coli O157:H7. Protective effects were evaluated by monitoring body weight loss, colon length, disease activity index (DAI), myeloperoxidase (MPO) activity, cytokine levels, tight junction protein expression, oxidative stress markers, and gut microbiota composition. M22-treated mice exhibited significantly less body weight loss and lower DAI scores than infected controls. M22 also prevented colon shortening, indicating reduced colonic damage. Probiotic treatment attenuated neutrophil infiltration and mucosal inflammation, as evidenced by decreased colonic MPO activity, reduced levels of pro-inflammatory cytokines, and elevated anti-inflammatory IL-10. Additionally, M22 preserved intestinal barrier function by upregulating tight junction proteins and mitigating infection-induced histopathological changes. M22 supplementation enhanced antioxidant defenses in colonic tissue (lower malondialdehyde, higher superoxide dismutase and glutathione), indicating reduced oxidative stress. Furthermore, gut microbiota analysis (16S rRNA sequencing) revealed that M22 counteracted infection-induced dysbiosis, restoring microbial diversity and a healthy composition (enrichment of beneficial commensals and suppression of harmful bacteria). By safeguarding intestinal integrity and homeostasis, M22 emerges as a promising next-generation probiotic for improving intestinal health in companion animals. Full article

Lactiplantibacillus plantarum is a versatile lactic acid bacterium (LAB) with broad ecological and metabolic adaptability, contributing to both technological and probiotic functions. The prevalence and functional diversity of locally adapted L. plantarum strains in traditional sourdough fermentations remain poorly understood. This study aimed to characterize ten L. plantarum strains isolated from traditional Estonian rye sourdoughs, focusing on safety, enzymatic and carbohydrate metabolism, fermentation performance, exopolysaccharide (EPS) production, and genotype-associated functional diversity, including interaction with aflatoxin B₁ (AFB₁). Strains were γ-hemolytic and susceptible to major antibiotics. Strong aminopeptidase and β-glucosidase activities were observed, whereas α-glucosidase and α-galactosidase activities varied among strains and genotypes. Strains efficiently utilized mono- and disaccharides, with genotype-specific patterns for complex carbohydrates. During sourdough fermentation, all strains acidified the dough (pH < 4.5) and produced lactic and acetic acids in optimal ratios, while fermentation kinetics differed in a genotype-dependent manner. EPS yields (131–225 mg/L) were stable across genotypes. All strains retained fermentative activity in the presence of AFB₁ and exhibited high binding capacity (~100%). These findings demonstrate the safety, metabolic versatility, and genotype-structured functional diversity of L. plantarum from traditional Estonian rye sourdoughs, supporting their application as robust, multifunctional starter cultures for sustainable food fermentations. Full article

Helicobacter pylori is a Gram-negative bacterium that inhabits the gastric mucosa and infects over 50% of the global population, predominantly in developing countries. The organism causes chronic gastritis and is associated with gastric carcinoma. Traditional antibiotic treatment promotes intestinal dysbiosis and antimicrobial resistance. In this context, postbiotics—the metabolic end products of probiotics—have been shown to be powerful antimicrobial alternatives. The excretion/secretion (E/S) products and exopolysaccharides (EPSs) of lactic acid bacteria (LAB) have been found to exhibit inhibitory activity against pathogens. EPSs are complex sugar polymers involved in biofilm formation and stress resistance, and their activity varies with culture conditions. Most notably, no digestible carbohydrates, such as those present in agave-derived Graminan-Type fructans (GTFs), are effective carbon sources for LAB, which, in turn, affects their metabolic end products. In this study, the E/S products and EPSs of the INP_MX_001 LAB strain were assayed for antimicrobial and antibiofilm activity after growth with three structurally different GTFs. Results indicated potent inhibition of H. pylori survival and biofilm formation in vitro. Our results confirm the promise of using LAB-derived postbiotics, particularly those produced with GTFs, as a novel, non-antibiotic means of combating H. pylori colonization and infection. Full article

This study assessed the performance and potential use of lactic acid bacteria (LAB) from Moroccan traditional foods as probiotics in animal feed. Five LAB strains Lactiplantibacillus plantarum from whey sourdough, Leuconostoc pseudomesenteroides and Leuconostoc mesenteroides from goat cheese, Enterococcus durans and Lacticaseibacillus casei from fermented milk were isolated and identified by 16S rRNA gene sequencing and MALDI-TOF mass spectrometry. Probiotic traits were evaluated by measuring acid/bile tolerance, cell surface hydrophobicity, emulsifying properties, antimicrobial activity and organic acid production, and safety checked through hemolysis and antibiotic sensitivity tests. L. plantarum, L. casei, and E. durans showed high survival rates after 24 h of culture under acid/bile stress conditions. The surface hydrophobicity of all strains ranged from 14.4 to 39.2%. L. plantarum showed the highest emulsifying capacity (81.4%) and stability (20%) after 24 h. Most strains inhibited pathogenic Staphylococcus epidermidis, Bacillus cereus, and Escherichia coli. Metabolite profiling revealed L. pseudomesenteroides as an interesting butyric acid-producing bacterium and L. plantarum as a remarkable strain releasing high content of organic acids. Their antibiotic susceptibility and non-hemolytic nature support their safety and potential use as feed additives. Full article

Listeriosis, the disease caused by the bacterium L. monocytogenes, can take invasive forms, with severe complications such as septicemia or meningitis, mainly affecting vulnerable people, such as pregnant women, the elderly, and immunocompromised people. The main transmission is through the consumption of contaminated food, and unpasteurized dairy products are common sources of infection. Due to the high mortality and the difficulty in eliminating the bacterium from the production environment, rigorous hygiene and control measures are essential to prevent the spread of Listeria in the food chain, and research on biofilm formation and bacterial resistance is vital to improve food safety. Dairy products, raw milk, and soft cheeses are among the most vulnerable to contamination with L. monocytogenes, especially due to pH values and low-temperature storage conditions. This paper presents a synthesis of the specialized literature on methods to reduce the incidence of L. monocytogenes in milk and dairy products. Conventional strategies, such as pasteurization and the use of chemical disinfectants, are effective but can affect food quality. Specialists have turned their attention to innovative and safer approaches, such as biocontrol and the use of nonthermal methods, such as pulsed electric fields, irradiation, and nanotechnology. Barrier technology, which combines several methods, has demonstrated superior efficiency in combating the bacterium without compromising product quality. Additionally, lactic acid bacteria (LAB) and bacteriocins are examples of biopreservation techniques that provide a future option while preserving food safety. Natural preservatives, especially those derived from plants and fruits, are promising alternatives to synthetic compounds. Future solutions should focus on developing commercial formulations that optimize these properties and meet consumer demands for healthy, environmentally friendly, and clean-label products. Full article

We identified strains of lactic acid bacteria from fermented potherb mustard that showed excellent fermentation properties. The goal was to identify superior starter cultures that would optimize the traditional fermentation process, reduce fermentation duration, and improve the quality of pickled potherb mustard. Four strains were screened: Weissella cibaria (LAB1, LAB3) and Leuconostoc mesenteroides (LAB2, LAB4). Then, after in vitro tests of tolerance to low pH and salt levels as well as lactic acid production ability, nitrite degradation ability, antibacterial properties, and antioxidant activity, LAB1 and LAB2 were selected as the best strains. Next, these two strains were used as starter cultures for fermenting potherb mustard. Each was inoculated into the fermentation solution. Compared to natural fermentation, both showed beneficial effects, including reducing nitrite content, shortening fermentation time, maintaining the reducing sugar, and increasing the levels of nitrogenous amino acids. Microbial diversity analyses revealed that, prior to fermentation, the predominant microbial communities were Methylobacterium and Sphingomonas, which primarily originated from the surrounding environment. However, 30 days after inoculation with the two strains, there was a significant increase in the abundance of Weissella and Lactobacillus, and Weissella emerged as the dominant bacterium. Inoculation of LAB1 effectively stabilized the bacterial community of the potherb mustard and significantly enhanced the content of nitrogenous amino acids in the final product, indicating that it is highly suitable as a mono-starter. On the other hand, LAB2 led to reduced nitrite content and facilitated the proliferation of Weissella and Lactobacillus, indicating that it is an effective mixed starter. Due to its limited effect on acid production, it is not recommended as a mono-starter for pickled mustard production. Full article

Lacticaseibacillus (L.) rhamnosus CRL75 is a lactic acid bacterium (LAB) isolated from local dairy products, demonstrating significant adaptation in skimmed milk (FM75). In this context, CRL75 exhibited high microbial growth (3.63 ± 0.18 log CFU·mL⁻¹), strong acidification (9.20 ± 0.10 g·L⁻¹ lactic acid, and 2.40 ± 0.10 pH units), and increased viscosity in FM75 after 16 h of fermentation. Additionally, this LAB strain produces both capsular polysaccharides (CPS+) and extracellular polysaccharides (EPS75), contributing to a ropy phenotype (>10 cm). The purified EPS75 (70.70 ± 3.25 mg·L⁻¹) displayed low molecular weight (12.7 kDa), with galactose and glucose as its primary monomers in a 4:1 ratio. In aqueous environments, EPS75 exhibited an extended size (147 nm), a random coil structure, and macromolecular aggregation. Furthermore, vibrational spectroscopy confirmed the presence of a neutral EPS with high thermal stability. Additionally, EPS75 exhibited dose-dependent antioxidant activity, effectively reducing metal ions (Fe³⁺, Mo⁶⁺, and Mn⁷⁺) and stabilizing radicals (ABTS^•+, HO^•, O₂^•−, and HOO^•). The biopolymer also demonstrated immunostimulatory and anti-inflammatory effects in RAW 264.7 cells. In vivo assays using Balb/c mice indicated that both EPS75 and FM75 prevented constipation, suggesting their potential as natural and safe agents for constipation-related disorders. Due to its viscosifying and health-promoting attributes, CRL75 offers promising applications for functional dairy products. Full article

This study aims to clarify the use of Limosilactobaillus reuteri (Lmb. reuteri) in dairy products, emphasizing its main characteristics and limitations through a comprehensive literature review. Lmb. reuteri, previously classified as Lactobacillus reuteri, is a lactic acid bacterium (LAB) generally present in the gastrointestinal tracts of humans and other animals, such as sheep, chickens, and rodents. Lmb. reuteri was reclassified as part of the genus Limosilactobacillus in April 2020, reflecting advancements in biomolecular research that identified distinct metabolic and biochemical characteristics among strains. This species is an important producer of reuterin, an antimicrobial compound facilitated through glycerol fermentation via specific enzymatic pathways. In addition, selected strains of Lmb. reuteri can be considered probiotic bacteria with numerous health benefits and that lead to well-being improvements. It is consistently related to improvements in gut health, immune function enhancement, and cholesterol reduction. Furthermore, its application in dairy products has gained prominence and is increasingly reported in the literature due to its technological and sensory benefits. Despite the challenges of its incorporation into the dairy matrix, largely due to the need to supplement these products, it has already demonstrated significant effects on several dairy products’ technological, sensory, and quality characteristics. Future research should address challenges like strain-specific efficacy and regulatory hurdles for the application of Lmb. reuteri in foods. Full article

Background: Listeria monocytogenes is a Gram-positive bacterium responsible for listeriosis, a serious foodborne disease that can lead to serious health complications. Pregnant women, newborns, the elderly, and patients with weakened immune systems are particularly susceptible to infection. Due to the ability of L. monocytogenes to survive in extreme environmental conditions, such as low temperatures, high salinity, and acidity, this bacterium poses a serious threat to food production plants and is particularly difficult to eliminate from these plants. One of the promising solutions to reduce the presence of this bacterium in food products is bacteriocins as natural control agents. These are substances with antibacterial activity produced by other bacteria, mainly lactic acid bacteria (LAB), which can effectively inhibit the development of pathogens such as L. monocytogenes. The use of bacteriocins in the food industry is beneficial due to their natural origin, specificity of action, and consumer safety. However, the problem of resistance to these substances exists. Results: This review focuses on the mechanisms of bacteriocin resistance, such as modifications of bacteriocin docking receptors, changes in the structure of the cell wall and membrane, and the occurrence of cross-resistance to different bacteriocins. Genetic factors determining these mechanisms and strategies to cope with the problem of resistance are also presented. Conclusions: Research on this issue is crucial for developing effective preventive methods that will enable the safe and long-term use of bacteriocins in food production. Full article

Lactic acid bacteria (LAB) are widely used to produce various food products, adding flavor, texture, and health benefits. The bacteria are commonly grown on expensive nutrients like glucose, sucrose, and yeast extracts, which makes them commercially unappealing. In the current study, Lactobacillus acidophilus TISTR 1338 culture was studied using spent cell yeast as a nitrogen source and molasses as a carbon source. The drying process used to create starter cultures of Lactobacillus acidophilus TISTR 1338 was vacuum drying. After vacuum drying, this bacterium had a survival rate of 8.08 log CFU/g. The dried strain survived for four months at 37 °C. With wasted cells at 0.5%, molasses concentration at 11% at 2.14 109 CFU/mL at 22 h, precise growth rate at 0.39 h⁻¹, and yield cell mass at 1.67 1011 CFU/g sugar, yeast produced the maximum cell mass. The lower viability of the tested strain was induced by a higher temperature during this prolonged storage. Meanwhile, dehydrated starter culture was subjected to accelerated storage testing at 50, 60, and 70 °C. To determine the vacuum-dried Lactobacillus acidophilus TISTR 1338′s long-term storage viability, a temperature-dependent prophecy model was created. Molasses and spent cell yeast serve as promising carbon and nitrogen sources when optimized conditions are employed. The study also suggests that vacuum drying is a promising method for producing dried cells suitable for non-refrigerated storage conditions. Full article

Food preservation techniques changed during the industrial revolution, as safer techniques were developed and democratized. However, one of the simplest techniques, adding salt, is still employed in a wide variety of products, not only as a flavor enhancer but as a method to allow for the controlled fermentation of products such as fruits. The objective of the present study consists of evaluating the quality of different salt-reduced fermented fruits through the application of the lactic acid bacteria (LAB) Lacticaseibacillus paracasei and vacuum, as well as assessing the LAB as a preventive measure against Escherichia coli O157:H7. To achieve this goal, microbial plate count techniques, the evaluation of the physicochemical characteristics, and Check-All-That-Apply/Rate-All-That-Apply sensory analyses were performed on bananas and apples individually fermented at 30 °C for 2 and 7 days, respectively. Additionally, a challenge test using E. coli as pathogenic bacteria was performed. The characteristics of each fruit determined the efficiency of the LAB’s protective activity. LAB-inoculated batches controlled the growth of E. coli in both salted fruits, but this pathogenic bacterium in the apple case was controlled even in the salt-reduced batch. Sensorially, only inoculated fermented apples found a reduction in off-flavor and old fruit smell; however, higher acceptability was found in the salt-reduced with LAB batches of both fruits. Thus, Lacticaseibacillus paracasei proved to be a cheap, easy, and feasible protective method that can ensure a protective strategy on salt-reduced fermented apples and should be studied particularly for different fruits. Full article

The presence of diverse carbohydrate-active enzymes (CAZymes) is crucial for the direct bioconversion of lignocellulose. In this study, various anaerobic microbial consortia were employed for the degradation of 10 g/L of minimally pretreated corncob. The involvement of lactic acid bacteria (LAB) and a CAZyme-rich bacterium (Bacteroides cellulosilyticus or Paenibacillus lautus) significantly enhanced the lactic acid production by Ruminiclostridium cellulolyticum from 0.74 to 2.67 g/L (p < 0.01), with a polysaccharide conversion of 67.6%. The supplement of a commercial cellulase cocktail, CTec 2, into the microbial consortia continuously promoted the lactic acid production to up to 3.35 g/L, with a polysaccharide conversion of 80.6%. Enzymatic assays, scanning electron microscopy, and Fourier transform infrared spectroscopy revealed the substantial functions of these CAZyme-rich consortia in partially increasing enzyme activities, altering the surface structure of biomass, and facilitating substrate decomposition. These results suggested that CAZyme-intensified consortia could significantly improve the levels of bioconversion of lignocellulose. Our work might shed new light on the construction of intensified microbial consortia for direct conversion of lignocellulose. Full article

Recently, prokaryotic laccases from lactic acid bacteria (LAB), which can degrade biogenic amines, were discovered. A laccase enzyme has been cloned from Oenococcus oeni, a very important LAB in winemaking, and it has been expressed in Escherichia coli. This enzyme has similar characteristics to those previously isolated from LAB as the ability to oxidize canonical substrates such as 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,6-dimethoxyphenol (2,6-DMP), and potassium ferrocyanide K₄[Fe(CN₆)], and non-conventional substrates as biogenic amines. However, it presents some distinctiveness, the most characteristic being its psychrophilic behaviour, not seen before among these enzymes. Psychrophilic enzymes capable of efficient catalysis at low temperatures are of great interest due to their potential applications in various biotechnological processes. In this study, we report the discovery and characterization of a new psychrophilic laccase, a multicopper oxidase (MCO), from the bacterium Oenococcus oeni. The psychrophilic laccase gene, designated as LcOe 229, was identified through the genomic analysis of O. oeni, a Gram-positive bacterium commonly found in wine fermentation. The gene was successfully cloned and heterologously expressed in Escherichia coli, and the recombinant enzyme was purified to homogeneity. Biochemical characterization of the psychrophilic laccase revealed its optimal activity at low temperatures, with a peak at 10 °C. To our knowledge, this is the lowest optimum temperature described so far for laccases. Furthermore, the psychrophilic laccase demonstrated remarkable stability and activity at low pH (optimum pH 2.5 for ABTS), suggesting its potential for diverse biotechnological applications. The kinetic properties of LcOe 229 were determined, revealing a high catalytic efficiency (kcat/Km) for several substrates at low temperatures. This exceptional cold adaptation of LcOe 229 indicates its potential as a biocatalyst in cold environments or applications requiring low-temperature processes. The crystal structure of the psychrophilic laccase was determined using X-ray crystallography demonstrating structural features similar to other LAB laccases, such as an extended N-terminal and an extended C-terminal end, with the latter containing a disulphide bond. Also, the structure shows two Met residues at the entrance of the T1Cu site, common in LAB laccases, which we suggest could be involved in substrate binding, thus expanding the substrate-binding pocket for laccases. A structural comparison of LcOe 229 with Antarctic laccases has not revealed specific features assigned to cold-active laccases versus mesophilic. Thus, further investigation of this psychrophilic laccase and its engineering could lead to enhanced cold-active enzymes with improved properties for future biotechnological applications. Overall, the discovery of this novel psychrophilic laccase from O. oeni expands our understanding of cold-adapted enzymes and presents new opportunities for their industrial applications in cold environments. Full article

The evaluation of the potentiality of lactic acid bacteria (LAB) strains isolated from fermented products to inhibit Botrytis cinerea and Escherichia coli O157:H7 growth on spinach and lettuce was conducted. From a total of forty LAB strains tested, three were selected due to their high inhibitory effect on plant pathogenic fungi. The identification of these isolates based on a 16S rRNA gene fragment sequence analysis confirmed the genus of Levilactobacillus sp. and Lactiplantibacillus sp. An effective method of coating LAB isolates on the lettuce and spinach surface was developed. The leaves were immersed in bacterial suspension (5.0 × 10⁶ cfu mL⁻¹) for 4 s and drained on tissue paper. LAB survived on lettuce and spinach leaves for 8 days at 6 log₁₀ cfu g⁻¹. Additionally, these bacteria decreased the number of filamentous fungi on the leaves. These isolates were found to inhibit the growth of B. cinerea and E. coli O157:H7 in vitro conditions in growing microbiological media. Their efficacy was confirmed in vivo conditions. These isolates inhibited the development of grey mould caused by B. cinerea on lettuce leaves. Two LAB isolates reduced the abundance of the pathogenic bacterium E. coli on spinach leaves by about 0.7 log₁₀ cfu g⁻¹. In glasshouse conditions, LAB stimulated the growth of examined plants. The lactic acid bacteria used in this study showed the capacity to be used as possible alternatives to chemical compounds in the protection of leafy vegetables against grey mould and for a decrease in E. coli O157:H7 contamination. Full article

We have previously shown that the lactic acid bacterium (LAB) Enterococcus avium G-15 produces gamma-aminobutyric acid (GABA) from monosodium l-glutamate (Glu) at a hyper conversion rate. We have also found a gene cluster, designated as a gad cluster, that consists of four genes for the conversion of Glu to GABA, a Glu–GABA antiporter, and two transcriptional regulatory proteins, GadR1 and GadR2. The present study has been designed to investigate what characteristics of the GadG enzyme may contribute to the high production of GABA and how these two regulators play a role in high GABA productivity. The kinetic study showed that compared with E. coli glutamate decarboxylase (GAD) enzymes, GadG has relatively high K_m (1.3–2.4 times) and k_cat (1.3–1.6 times) values, indicating that although there are no remarkable differences in kinetic parameters between the three GAD enzymes, GadG may contribute to the high production of GABA in the presence of enough substrates. Further, the G-15 strain lacks the ornithine decarboxylase pathway-based acid resistance mechanism observed in some LAB strains, suggesting that the GAD-based acid resistance system is relatively important and may be vigorously employed in the G-15 strain. The molecular biological analysis of GadR1 revealed that the protein plays a role in GABA production as a transcriptional activator through an indirect pathway. Full article