Lactobacillus brevis CD2: Fermentation Strategies and Extracellular Metabolites Characterization

Improving the bacterial community, flavor, and safety properties of northeastern sauerkraut by inoculating autochthonous Levilactobacillus brevis

The effect of Levilactobacillus brevis as a starter in northeastern sauerkraut fermentation is still unknown, and further evaluation is worthwhile. Hence, this study aimed to evaluate the effect of autochthonous L. brevis inoculation on the bacterial community succession and formation of flavor and harmful substances in sauerkrauts. Inoculation with L. brevis lowered the pH and increased the total acid content of sauerkrauts (P < 0.05). The nitrite content of the inoculated sauerkraut was significantly lower than that of control (P < 0.05). Moreover, the spoilage bacteria of the inoculated sauerkraut were decreased and nitrogen metabolism was improved. The contents of aldehydes, alcohols, esters, acids, and alkanes increased significantly (P < 0.05), and the sensory attributes such as aroma, sourness, and gloss were also improved. L. brevis was positively and negatively correlated with flavor metabolites and nitrite, respectively, which proved to be a potential starter culture to manufacture sauerkraut.

Efficacy of the Probiotic L. brevis in Counteracting the Demineralizing Process of the Tooth Enamel Surface: Results from an In Vitro Study

BACKGROUND

Enamel plays an essential role in protecting the underlying layers of the human tooth; therefore, preserving it is vital. This experimental study aimed to evaluate the potential ability of L. brevis to counteract the action of a demineralizing agent on dental enamel morphology and mineral composition in vitro.

METHODS

The sample consisted of 12 healthy human posterior teeth. The coronal portion of each tooth was subdivided into two equal parts longitudinally. The specimens were randomly divided into four groups: artificial saliva, L. brevis suspension, demineralizing agent (DA), and DA plus L. brevis. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to evaluate the surface micromorphology and the mineral content, respectively. The statistical analysis was conducted using a one-way ANOVA, followed by Tukey's post hoc test.

RESULTS

SEM analysis did not highlight significant changes in the enamel microstructure of L. brevis-treated specimens compared to the control. DA-induced damage to the enamel structure was drastically reduced when the specimens were contextually exposed to the probiotic. The treatment with DA substantially reduced the weight % of crucial enamel minerals, i.e., Ca and P. Notably, the probiotic was able to reverse the demineralization process, bringing Ca and P weight % back to basal levels, including the Ca/P ratio.

CONCLUSIONS

The findings indicate that L. brevis is able to efficiently protect the dental enamel surface from the damage caused by DA and increase the enamel resistance to demineralization. Overall, L. brevis confirms its efficacy in preventing or counteracting the action of carious lesions through a novel mechanism that protects the tooth surface under a chemical challenge that mimics the caries process.

Vegan grade medium component screening and concentration optimization for the fermentation of the probiotic strain Lactobacillus paracasei IMC 502® using Design of Experiments

Lactobacillus paracasei IMC502® is a commercially successful probiotic strain. However, there are no reports that investigate growth medium composition in relation to improved biomass production for this strain. The major outcome of the present study is the design and optimization of a growth medium based on vegan components to be used in the cultivation of Lactobacillus paracasei IMC502®, by using Design of Experiments. Besides comparing different carbon sources, the use of plant-based peptones as nitrogen sources was considered. In particular, the use of guar peptone as the main nitrogen source, in the optimization of fermentation media for the production of probiotics, could replace other plant peptones (e.g. potato, rice, wheat, and soy) which are part of the human diet, thereby avoiding an increase in product and process prices. A model with R2 and adjusted R2 values higher than 95% was obtained. Model accuracy was equal to 94.11%. The vegan-optimized culture medium described in this study increased biomass production by about 65% compared to growth on De Man-Rogosa-Sharpe (MRS) medium. Moreover, this approach showed that most of the salts and trace elements generally present in MRS are not affecting biomass production, thus a simplified medium preparation can be proposed with higher probiotic biomass yield and titer. The possibility to obtain viable lactic acid bacteria at high density from vegetable derived nutrients will be of great interest to specific consumer communities, opening the way to follow this approach with other probiotics of impact for human health.

From Traditional Dairy Product "Katak" to Beneficial Lactiplantibacillus plantarum Strains

Traditional milk products, widely consumed in many countries for centuries, have been drawing renewed attention in recent years as sources of bacteria with possible bioprotective properties. One such product for which only limited information exists is the traditional Bulgarian "katak". This fermented yogurt-like product, renowned for its taste and long-lasting properties, possesses specific sensory characteristics. In this study, 18 lactic acid bacteria (LABs) were isolated from artisanal samples made in the Northwest part of Bulgaria. A polyphasic taxonomic approach combining classical phenotypic and molecular taxonomic methods, such as multiplex PCR, 16S rDNA sequencing, and MALDI-TOF MS, was applied, leading to the identification of 13 strains. The dominance of Lactiplantibacillus plantarum was confirmed. In vitro tests with the identified strains in model systems showed a promising broad strain-specific spectrum of activity against food-borne and human pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli). Non-purified Lactobacillus postbiotics, produced during fermentation in skimmed and soya milks and in MRS broth, were estimated as limiting agents of virulence factors. The LAB's production of lactate, acetate, and butyrate is a promising probiotic feature. A further characterization of the active strains and analysis of the purified post-metabolites are needed and are still in progress.

Exploring the effects of the fermentation method on the quality of Lycium barbarum and Polygonatum cyrtonema compound wine based on LC-MS metabolomics

This study aimed to examine the effect of fermentation methods on the quality of Lycium barbarum and Polygonatum cyrtonema compound wine (LPW) by combining non-targeted metabolomic approaches with chemometrics and path profiling to determine the chemical and metabolic properties of LPW. The results demonstrated that SRA had higher leaching rates of total phenols and flavonoids, reaching 4.20 ± 0.10 v/v ethanol concentration. According to LC-MS non-targeting genomics, the metabolic profiles of LPW prepared by different mixtures of fermentation methods (Saccharomyces cerevisiae RW; Debaryomyces hansenii AS2.45) of yeast differed significantly. Amino acids, phenylpropanoids, flavonols, etc., were identified as the differential metabolites between different comparison groups. The pathways of tyrosine metabolism, biosynthesis of phenylpropanoids, and metabolism of 2-oxocarboxylic acids enriched 17 distinct metabolites. SRA stimulated the production of tyrosine and imparted a distinctive saucy aroma to the wine samples, providing a novel research concept for the microbial fermentation-based production of tyrosine.

Effect of Levilactobacillus brevis as a starter on the flavor quality of radish paocai

The aim of this study was to investigate the effectiveness of Levilactobacillus brevis on the fermentation kinetics and flavor quality of radish paocai. Compared with spontaneous fermentation (SF), the radish paocai of inoculated fermentation (IF) using Levilactobacillus brevis PL6-1 as a starter could rapidly utilize sugar to produce acid, thus accelerating the fermentation process. The texture including hardness, chewiness, and springiness of the IF were all higher than that of the SF, and the IF paocai showed higher L value in color. L. brevis PL6-1 as a starter could increase the final levels of metabolites of mannitol (5.43 mg/g), lactic acid (543.44 mg/100 g) and acetic acid (87.79 mg/100 g). Fifteen volatile organic compounds (VOCs) were identified as key aroma-active compounds in radish paocai and 8 differential VOCs were considered as the potential markers. L. brevis PL6-1 could improve the levels of 1,8-cineole, 1-hexanol, hexanoic acid, 2-methoxy-4-vinylphenol, and eugenol, giving the radish paocai floral, sweet, and sour aroma, and reduce the unpleasant odor of garlic, onion, and pungent, contributed by erucin, diallyl disulfide, and allyl trisulfide. Sensory evaluation results showed that the appearance, taste, texture, and overall acceptability of IF paocai were all better than the SF group. Therefore, L. brevis PL6-1 could be a potential starter to improve the flavor and sensory quality for radish paocai fermentation.

Optimization of growth of Levilactobacillus brevis SP 48 and in vitro evaluation of the effect of viable cells and high molecular weight potential postbiotics on Helicobacter pylori

Several Levilactobacillus brevis strains have the potential to be used as probiotics since they provide health benefits due to the interaction of live cells, and of their secreted products, with the host (tissues). Therefore, the development of simple fermentation processes that improve cell viability to reduce industrial production costs, and at the same time the characterization and biological evaluation of cell-free postbiotics that can further promote application, are of great interest. In the present study, small scale batch fermentations on semi defined media, deprived of animal derived raw materials, were used to optimize growth of L. brevis SP48, reaching 1.2 ± 0.4 × 1010 CFU/ml of viable cells after 16 h of growth. Displacement, competition, and inhibition assays compared the effect, on Helicobacter pylori, of L. brevis cells to that of its partially purified potentially postbiotic fraction rich in exopolysaccharides and proteins. The expression of pro and anti-inflammatory biochemical markers indicated that both samples activated antimicrobial defenses and innate immunity in a gastric model. Moreover, these compounds also acted as modulators of the inflammatory response in a gut in vitro model. These data demonstrate that the high molecular weight compounds secreted by L. brevis SP48 can contrast H. pylori and reduce inflammation related to intestinal bowel disease, potentially overcoming issues related to the preservation of probiotic viability.

Genetically engineered bacterium: Principles, practices, and prospects

Advances in synthetic biology and the clinical application of bacteriotherapy enable the use of genetically engineered bacteria (GEB) to combat various diseases. GEB act as a small ‘machine factory’ in the intestine or other tissues to continuously produce heterologous proteins or molecular compounds and, thus, diagnose or cure disease or work as an adjuvant reagent for disease treatment by regulating the immune system. Although the achievements of GEBs in the treatment or adjuvant therapy of diseases are promising, the practical implementation of this new therapeutic modality remains a grand challenge, especially at the initial stage. In this review, we introduce the development of GEBs and their advantages in disease management, summarize the latest research advances in microbial genetic techniques, and discuss their administration routes, performance indicators and the limitations of GEBs used as platforms for disease management. We also present several examples of GEB applications in the treatment of cancers and metabolic diseases and further highlight their great potential for clinical application in the near future.

Limosilactobacillus fermentum from buffalo milk is suitable for potential biotechnological process development and inhibits Helicobacter pylori in a gastric epithelial cell model

•

L.fermentum from buffalo milk grows efficiently without animal-derived medium components.

•

Highest viable biomass titers can be reached after only 8h improving productivity.

•

L. fermentum is suitable for large scale production: complete biotech approach.

•

L. fermentum demonstrates 60% cell survival after spray drying.

•

L. fermentum from buffalo milk displaces H. pylori in a gastric epithelial cell model.

Probiotics are living microorganisms that give beneficial health effects while consumed, and each strain possesses diverse and unique properties and also different technological characteristics that affect its ability to be produced at large scale. Limosilactobacillus fermentum is a widely studied member of probiotics, however, few data are available on the development of fermentation and downstream processes for the production of viable biomasses for potential industrial applications.

In the present study a novel L. fermentum strain was isolated from buffalo milk and used as test example for biotechnological process development. The strain was able to produce up to 10⁹ CFU/mL on a (glucose based) semi-defined medium deprived of animal-derived raw materials up to the pilot scale (150 L), demonstrating improved results compared to commonly used, although industrially not suitable, media rich of casein and beef extract. The study of strain behavior in batch experiments indicated that the highest concentration of viable cells was reached after only 8 h of growth, greatly shortening the process. Moreover, initial concentrations of glucose in the medium above 30 g/L, if not supported by higher nitrogen concentrations, reduced the yield of biomass and increased production of heterolactic fermentation by-products. Biomass concentration via microfiltration on hollow fibers, and subsequent spray-drying allowed to recover about 5.7 × 10¹⁰CFU/g_powder of viable cells, indicating strain resistance to harsh processing conditions.

Overall, these data demonstrate the possibility to obtain and maintain adequate levels of viable L. fermentum cells by using a simple approach that is potentially suitable for industrial development. Moreover, since often exopolysaccharides produced by lactobacilli contribute to the strain's functionality, a partial characterization of the EPS produced by the newly identified L. fermentum strain was carried out.

Finally, the effect of L. fermentum versus H. pylori in a gastric epithelial cell model was evaluated demonstrating its ability to stimulate the response of the immune system and displace the infective agent.