Antibacterial and anticavity activity of probiotic Lactobacillus plantarum 200661 isolated from fermented foods against Streptococcus mutans

Treatment of dental biofilm-forming bacterium Streptococcus mutans using tannic acid-mediated gold nanoparticles

Biosynthesized gold nanoparticles (AuNPs) are highly attracted as a biocompatible nanodrug to treat various diseased conditions in humans. In this study, phytochemical tannic acid-mediated AuNPs (TA-AuNPs) are successfully synthesized and tested for antibacterial and antibiofilm activity against dental biofilm-forming Streptococcus mutans biofilm. The synthesized TA-AuNPs are appeared as spherical in shape with an average size of 19 nm. The antibacterial potential of TA-AuNPs was evaluated using ZOI and MIC measurements; while, antibiofilm efficacy was measured by checking the eradication of preformed biofilm on the tooth model. The ZOI and MIC values for TA-AuNPs are 25 mm in diameter and 4 μg/mL, respectively. The MTT assay, CLSM, and SEM results demonstrate that the preformed S. mutans biofilm is completely eradicated at 4xMIC (16 μg/mL) of TA-AuNPs. Finally, the present study reveals that the synthesized TA-AuNPs might be a great therapeutic drug to treat dental biofilm-forming bacterium S. mutans.

Antioxidant and Antibacterial Activities of Nano-probiotics Versus Free Probiotics Against Gastrointestinal Pathogenic Bacteria

Antibiotic-resistant pathogenic bacteria and the oxidative stress related to their infections are dangerous health problems. Finding new safe, effective antibacterial and antioxidant agents is an urgent global need. Probiotics are a strong candidate for possible antibacterial and antioxidant agents. The delivery of these probiotics without any effect on gastrointestinal digestion is the most important point for their application. The encapsulation of the probiotics on nanoparticles or other supports is a well-known method for the safe delivery of the probiotics. Little information is known about the effect of the probiotic encapsulation on its antibacterial and antioxidant activity. The present study tried to investigate the effect of probiotic encapsulation on nano-chitosan on its antioxidant activity and antibacterial activity against some pathogenic bacteria. We encapsulated some known probiotic species on nano-chitosan and investigated the antibacterial activity of the nano-probiotics and free probiotics against gastrointestinal pathogenic bacteria. The antioxidant characters of the free and encapsulated probiotics were investigated in terms of DPPH radicle scavenging activity, ferric ion chelating activity, hydroxyl radicle scavenging activity, superoxide anion radicle scavenging activity, and anti-lipid peroxidation activity. Results showed the superiority of the encapsulated probiotics as antibacterial and antioxidant agents over the free ones. The encapsulation improved the antibacterial activity of Sporolactobacillus laevolacticus against Bacteroides fragilis by 134% compared to the free one. Also, significantly, the encapsulation increased the hydroxyl radicle scavenging activity of Enterococcus faecium by about 180% compared to the free one. Nano-chitosan encapsulation synergistically increased the antioxidant and antibacterial activity of the studied probiotics. This can be promising for controlling pathogenic bacteria.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01140-2.

Probiotic Lactobacillus plantarum Ln4 Showing Antimicrobial and Antibiofilm Effect against Streptococcus mutans KCTC 5124 Causing Dental Caries

Dental caries has known as an infectious disease that is considered a serious global public health problem. Recently, report indicate that probiotics play a vital role in maintaining oral health. Therefore, this study aimed to evaluate the prevention effects of Lactobacillus plantarum Ln4 against dental infection by the pathogenic bacterium Streptococcus mutans KCTC 5124 through biofilm formation inhibition. To evaluate such prevention effects against S. mutans KCTC 5124, antimicrobial activity, auto-aggregation, co-aggregation, cell surface hydrophobicity, total exopolysaccharide (EPS) production rate, and biofilm formation were analyzed. Results showed that L. plantarum Ln4 showed higher antimicrobial activity than L. rhamnosus GG (LGG). In the group treated with L. plantarum Ln4, the co-aggregation (58.85%), cell surface hydrophobicity (16.75%), and EPS production rate (73.29%) values were lower than those of LGG and the negative control. Additionally, crystal violet staining and confocal laser scanning microscopy (CLSM) revealed that L. plantarum Ln4 effectively inhibited biofilm formation in S. mutans KCTC 5124. Therefore, L. plantarum Ln4 could be used in the industry as a probiotics to prevent and improve oral health.

The inhibitory effect of ovomucoid from egg white on biofilm formation by Streptococcus mutans

BACKGROUND

Streptococcus mutans, the main pathogen associated with tooth decay, forms cariogenic biofilms on tooth surfaces. Therefore, controlling oral biofilm helps prevent dental caries. Hen's egg is a nutrient-dense food, and egg white is a good source of protein. Ovomucoid is one of the major proteins in egg white, with a 28 kDa molecular weight. The present study aimed to investigate the inhibitory effects of ovomucoid on the biofilm formation of S. mutans by suppressing virulence factors, including bacterial adherence, cellular aggregation and exopolysaccharide (EPS) production.

RESULTS

Crystal violet staining showed that biofilm formation by S. mutans was inhibited by ovomucoid at 0.25-1 mg mL-1 levels. Field emission scanning electron microscopy also confirmed this inhibition. In addition, ovomucoid reduced mature biofilm, water-insoluble EPS synthesis and the metabolic activity of bacterial cells in the biofilm. The bacterial adhesion and aggregation abilities of S. mutans were also decreased in the presence of ovomucoid. Ovomucoid downregulated the expression of comDE and vicR genes involved in the two-component signal transduction system and gtfA and ftf genes involved in EPS production.

CONCLUSION

Ovomucoid has the potential for use as an anti-biofilm agent for dental caries treatment because of its inhibitory effects on the virulence factors of S. mutans. © 2023 Society of Chemical Industry.

Complete genome analysis of Lactiplantibacillus plantarum VHProbi P06, a novel probiotic that resists Streptococcus pneumoniae in the upper respiratory tract

The purpose of this study was to screen lactic acid bacteria active against Streptococcus pneumoniae and to analyze the genetic basis of their probiotic functions from the genome. We isolated a novel Lactiplantibacillus plantarum VHProbi P06 from pickles, which showed strong antibacterial activity against S. pneumoniae, adhesion to 5-8F cells, and inhibition of S. pneumoniae colonization in the respiratory tract. Genome of VHProbi P06 was analyzed, we found one class II bacteriocin synthesis gene cluster. Genome of the strain contained 42 adhesion-related protein-coding genes, and implicated three exopolysaccharide biosynthesis gene clusters with low homologous to L. plantarum WCFS1. Moreover, VHProbi P06 possessed 3 intact phage regions and 117 Carbohydrate Active Enzyme genes. By comparing the genomes of five L. plantarum, 275 unique genes were found in VHProbi P06. Finally, the gene prediction was verified, the bacteriocin PlnJK produced by P06 was identified by LC-MS/MS, and the laminar exopolysaccharide with a weight-averaged molecular of 125.37 KDa was also found. This study provides a theoretical basis for the application of VHProbi P06 to the upper respiratory tract to resist pathogenic bacteria.

Antagonistic activity of Lactobacillus spp. and Bifidobacterium spp. against cariogenic Streptococcus mutans in vitro and viability when added to chewing gum during storage

The aim of the work was to evaluate antagonistic activity of Lactobacillus spp. and Bifidobacterium spp. in vitro against cariogenic Streptococcus mutans UA 159 and viability in chewing gum, during storage. Antagonistic activity was evaluated in vitro by the "spot on the lawn" test. Two bacteria were chosen and subjected to lyophilization and microencapsulation using the atomization method, containing polyvinylpyrrolidone polymer and lactose as encapsulating agents. For application in food matrices, four treatments were elaborated: chewing gum containing lyophilized B. lactis B94 (BLL), microencapsulated B. lactis B94 (BLE), lyophilized L. brevis (LBL), and microencapsulated L. brevis (LBE). Both microorganisms demonstrated a high capacity for inhibition against S. mutans, when compared to oral antiseptic chlorhexidine 0.2% in vitro, and according to the test of sensitivity profile to proteolytic enzymes, all the bacteria tested are producers of antimicrobial peptides, resulting in the inhibitory activity of the cariogenic bacterium. Furthermore, the viability of B. lactis B94 and L. brevis was maintained after microencapsulation, indicating that the process was efficient, with no significant difference (p < 0.05) between the results. And, in the chewing gum containing the bacteria during the storage period (33 days), it was found that cell immobilization did not significantly influence (p < 0.05) the counts of L. brevis but benefited the viability of B. lactis B94. Therefore, both probiotic bacteria are producers of antimicrobial substances with the ability to inhibit S. mutans, in vitro. The microencapsulation was considered efficient since it influenced the viability of B. lactis B94 (> 8 log CFU/g); however, the microencapsulation did not influence the viability of L. brevis since in both lyophilized and encapsulated form; the concentration of the bacteria remained above 8 log CFU/g during the storage period of the chewing gum.

Alleviation of dental caries by use of isolated potential probiotic and its characterization

Streptococcus mutans plays a major role in biofilm formation and pathogenic bacterial adhesion. Here we investigated the abilities of our isolates from diverse conventional sources to characterize the beneficial bacteria for inhibition of S. mutans. Enterobacter cloacae PS-74, a beneficial bacteria isolated from yoghurt, is gram negative, rod shaped, and resistant to acid, bile salt, and amylase. PS-74 cell-free supernatants (CFS) demonstrated highest zone of inhibition of 29 ± 1.7 mm. Further, the minimum inhibitory concentration (MIC) value of CFS PS-74 was recorded to be 10 μL and its minimum bactericidal concentration (MBC) value was found to be 15μL which led to 99.9% log reduction of S. mutans. Moreover, the biofilm formation was reduced by 84.91% at MIC15 of CFS PS-74 which alleviate the dental caries formation by S. mutans. This is the first report on E. cloacae PS-74, which was studied for its probiotic properties to inhibit S. mutans MTCC-890 due to the production of organic acids and employed in oral treatment.

In Silico Probiogenomic Characterization of Lactobacillus delbrueckii subsp. lactis A4 Strain Isolated from an Armenian Honeybee Gut

A Lactobacillus delbrueckii ssp. lactis strain named A4, isolated from the gut of an Armenian honeybee, was subjected to a probiogenomic characterization because of its unusual origin. A whole-genome sequencing was performed, and the bioinformatic analysis of its genome revealed a reduction in the genome size and the number of the genes-a process typical for the adaptation to endosymbiotic conditions. Further analysis of the genome revealed that Lactobacillus delbrueckii ssp. lactis strain named A4 could play the role of a probiotic endosymbiont because of the presence of intact genetic sequences determining antioxidant properties, exopolysaccharides synthesis, adhesion properties, and biofilm formation, as well as an antagonistic activity against some pathogens which is not due to pH or bacteriocins production. Additionally, the genomic analysis revealed significant potential for stress tolerance, such as extreme pH, osmotic stress, and high temperature. To our knowledge, this is the first report of a potentially endosymbiotic Lactobacillus delbrueckii ssp. lactis strain adapted to and playing beneficial roles for its host.

Probiotic Weissella cibaria displays antibacterial and anti-biofilm effect against cavity-causing Streptococcus mutans

Streptococcus mutans is a significant contributor to dental caries and causes functional and aesthetic discomfort. Weissella cibaria strains were isolated from kimchi, and their functional properties were determined. In this study, the antibacterial and antibiofilm effects of four W. cibaria strains (D29, D30, D31, and B22) were evaluated against three S. mutans strains using culture fluid and cell-free supernatants. The results showed that W. cibaria reduced the exopolysaccharides production and auto-aggregation, increased co-aggregation, and downregulated virulence factors, leading to the inhibition of bacterial growth and biofilm formation. These findings were confirmed using scanning electron microscopy and confocal laser scanning microscopy. These results indicate that oral health can be potentially improved by W. cibaria.

Purification of exopolysaccharides from Lactobacillus rhamnosus and changes in their characteristics by regulating quorum sensing genes via polyphenols

To explore the effect of Lonicera caerulea fruit polyphenols (LCP) on caries-causing bacteria, strain RYX-01 with high production of biofilm and exopolysaccharides (EPS) was isolated from the oral cavity of caries patients and was identified as Lactobacillus rhamnosus by 16S rDNA analysis and morphology. The characteristics of EPS produced by RYX-01 (EPS-CK) and those produced by adding L. caerulea fruit polyphenols (EPS-LCP) were compared to reveal whether LCP reduced the cariogenicity of RYX-01 by influencing the structure and composition of EPS. The results showed that LCP could increase the content of galactose in EPS and destroy the original aggregation state of EPS-CK but had no significant effect on the molecular weight and functional group composition of EPS (p > 0.05). At the same time, LCP could inhibit the growth of RYX-01, reduce EPS and biofilm formation and inhibit the expression of quorum sensing (QS, luxS)- and biofilm formation (wzb)-related genes. Therefore, LCP could change the surface morphology, content and composition of RYX-01 EPS and reduce the cariogenic effect of EPS and biofilm. In conclusion, LCP can be used as a potential plaque biofilm inhibitor and QS inhibitor in drugs and functional foods.

Adjunctive role of Q10 with Ligilactobacillus salivarius, and Lactiplantibacillus plantarum probiotic Bacteria on the HEp-2 cells viability and adhesion of Streptococcus mutans

Objective

Various studies have indicated the application of Coenzyme Q10 and probiotic bacteria such as Ligilactobacillus salivarius (L. salivarius) and Lactiplantibacillus plantarum (L. plantarum) in combating periodontal disease. Considering the positive effect of these two on oral health, and the destructive effect of S. mutans, in this study, we investigate the outcomes of the administration of probiotics and Q10 on infected HEp-2 cell viability and S. mutans adhesion in different settings.

Methods

A 3-week-old human epidermoid laryngeal (HEp-2) cell line was cultured and exposed to two different probiotics and 3 different doses of Q10 doses. Samples were contaminated by S. mutans immediately (therapeutic setting) and after 3 hours (preventive setting). Eventually, the viability of HEp-2 cells was investigated by MTT. Also, the number of adhered S. mutans was explored by direct and indirect adhesion assays.

Results

L. plantarum and L. salivarius protect epithelial cells against S. mutans in both therapeutic and preventive settings, albeit not fully. In contrast, Q10 completely preserves the viability of infected Her HEp-2 cells at all concentrations. The effects of the coexistence of Q10 and probiotics were not quite equal, among which L. salivarius and 5 μg of Q10 form the best results. The microscopic adherence assay of S. mutans revealed that samples containing Q10 had significantly lower adhesion of probiotics and S. mutans to HEp-2 cells. Similarly, plates containing L. salivarius with 5μg or L. plantarum with 1μg Q10 or sole presence of L. salivarius had the lowest S. mutans adherence among others. Also, L. salivarius with 5μg Q10 had one of the highest probiotic adherences.

Conclusion

In conclusion, co-administration of Q10 and probiotics especially in presence of L. salivarius with 5μg Q10 could have remarkable effects on HEp-2 cell viability, S. mutans, and probiotic adherence. Nevertheless, our study, for the first time, showed that Q10 might have an anti-bacterial activity by suppressing the adhesion of tested bacteria to HEp-2 cells. This hypothesis, if correct, suggests that due to their different mechanisms, co-prescription of Q10 and probiotics may lead to better clinical responses, especially in the mentiond dose.

Significant Differences in Gut Microbiota Between Irritable Bowel Syndrome with Diarrhea and Healthy Controls in Southwest China

BACKGROUND

Irritable bowel syndrome (IBS) is a heterogeneous disease, which is closely related to environmental factors and gut microbiota.

OBJECTIVE

To study gut microbiota in IBS-D of Han nationality in Southwest China and explore its relationship with environmental factors.

METHODS

One hundred and twenty cases of IBS-D and 63 cases of HCs were recruited; baseline data such as age, height, and weight were collected. HAMA, HAMD, IBS-SSS, IBS-QOL, and laboratory tests were performed. Feces were collected for 16S rDNA sequencing. Then, the differences of gut microbiota were analyzed and looked for biomarkers of each. FAPROTAX was used to predict the functional differences of gut microbiota. Spearman analysis was conducted between the phylum level and environmental factor.

RESULTS

There were significant differences in daily life between IBS-D and HCs, especially in the spicy taste. The scores of HAMA and HAMD, urea, and transaminase in IBS-D were significantly higher than those of HCs. The richness of gut microbiota in IBS-D was significantly lower than that of HCs, as well as the beta diversity, but not diversity. The biomarkers of IBS-D were Prevotella, Clostridiales, and Roseburia, and the biomarkers of HCs were Veillonellaceae, Bacteroides coprocola, and Bifidobacteriales. The functions of gut microbiota in IBS-D were significantly different from HCs. Correlation analysis showed that multiple gut microbiota were closely related to HAMA, IBS-SSS, IBS-QOL, inflammatory indexes, and liver enzymes.

CONCLUSION

There are significant differences in richness of gut microbiota, flora structure, and flora function between IBS-D and HCs in Southwest China. These differences may be closely related to environmental factors such as eating habits, living habits, and mental and psychological factors.

CLINICAL TRIAL REGISTRATION

The trial was registered and approved in China Clinical Trial Registry (Registration No. ChiCTR2100045751).

Characterization and potential oral probiotic properties of Lactobacillus plantarum FT 12 and Lactobacillus brevis FT 6 isolated from Malaysian fermented food

OBJECTIVE

This study aims to characterise the lactic acid bacteria (LAB) isolated from local Malaysian fermented foods with oral probiotics properties.

DESIGN

The LAB strains isolated from Malaysian fermented foods, Lactobacillus brevis FT 6 and Lactobacillus plantarum FT 12, were assessed for their antimicrobial properties against Porphyromonas gingivalis ATCC 33277 via disc diffusion assay. Anti-biofilm properties were determined by treating the overnight P. gingivalis ATCC 33277 biofilm with different concentrations of LAB cell-free supernatant (LAB CFS). Quantification of biofilm was carried out by measuring the optical density of stained biofilm. The ability of L. brevis FT 6 and L. plantarum FT 12 to tolerate salivary amylase was also investigated. Acid production with different sugars was carried out by pH measurement and screening for potential antimicrobial organic acid by disc diffusion assay of neutralised probiotics CFS samples. In this study, L. rhamnosus ATCC 7469, a commercial strain was used to compare the efficacy of the isolated strain with the commercial strain.

RESULTS

Lactobacillus brevis FT 6 and L. plantarum FT 12 possess antimicrobial activity against P. gingivalis with inhibition diameters of more than 10 mm, and the results were comparable with L. rhamnosus ATCC 7469. The MIC and MBC assay results for all tested strains were recorded to be 25 µl/µl concentration. All LAB CFS reduced biofilm formation proportionally to the CFS concentration and tolerated salivary amylase with more than 50% viability. Overnight cultures of all lactic acid bacteria strains showed a pH reduction and neutralised CFS of all lactic acid bacteria strains did not show any inhibition towards P. gingivalis.

CONCLUSIONS

These results indicate that the isolated probiotics have the potential as probiotics to be used as a supportive oral health treatment, especially against a periodontal pathogen, P. gingivalis.

Screening and Molecular Identification of Lactic Acid Bacteria Producing β-Glucan in Boza and Cider

The goal of this study was screening and molecular identification of Lactic Acid Bacteria (LAB) producing β-glucan from different species isolated from boza and cider compared to a standard strain for Lactobacillus rhamnosus NRRL 1937 (LGG). From 48 unknown isolates, four LAB strains were selected. Based on the NCBI database, their nomenclature was A3, B6, and C9 for Limosilactobacillus fermentum SH1, SH2, and SH3 along with D6 for Leuconostoc mesenteroides SH4. Also, their similarity values were 100%, 99.8%, 100%, and 100%, respectively. The potential of Exopolysaccharide (EPS) (as β-glucan) production for selected LAB strains by gtf gene, conventional PCR and gene expression using both LGG as a control and LAB 16S rRNA gene as a house-keeping gene was investigated. In addition, EPS (mg/100 mL), cell mass (mg/100 mL), pH, total carbohydrate%, total protein% and β-glucan% by the HPLC for all selected LAB isolates were studied. All results of genetic and chemical tests proved the superiority of B6 treatment for L. fermentum SH2. The results showed the superiority of B6 treatment in gtf gene expression (14.7230 ± 0.070-fold) followed by C9 and A3 treatments, which were 10.1730 ± 0.231-fold and 8.6139 ± 0.320-fold, respectively. while D6 treatment recorded the lowest value of gene expression (0.8566 ± 0.040-fold) compared to the control LGG (one-fold). The results also demonstrated that B6 treatment was superior to the other treatments in terms of EPS formation, with a value of 481 ± 1.00 mg/100 mL, followed by the C9 treatment at 440 ± 2.00 mg/100 mL, compared to the LGG (control) reaching 199.7 ± 3.51 mg/100 mL. Also, the highest % of quantitative and qualitative β-glucan in EPS was observed in B6 followed by C9, D6 and A3 which were 5.56 ± 0.01%, 4.46 ± 0.01%, 0.25 ± 0.008% and 0.12 ± 0.008%, respectively compared to control (0.31 ± 0.01%). Finally, the presented results indicate the importance of screening the local LAB isolates to obtain a superior strain for β-glucan production which will be introduced in a subsequent study under optimum conditions.

Leuconostoc mesenteroides LVBH107 Antibacterial Activity against Porphyromonas gingivalis and Anti-Inflammatory Activity against P. gingivalis Lipopolysaccharide-Stimulated RAW 264.7 Cells

Probiotics, active microorganisms benefiting human health, currently serve as nutritional supplements and clinical treatments. Periodontitis, a chronic infectious oral disease caused by Porphyromonas gingivalis (P. gingivalis), activates the host immune response to release numerous proinflammatory cytokines. Here, we aimed to clarify Leuconostoc mesenterica (L. mesenteroides) LVBH107 probiotic effects based on the inhibition of P.gingivalis activities while also evaluating the effectiveness of an in vitro P.gingivalis lipopolysaccharide-stimulated RAW 264.7 cell-based inflammation mode. L. mesenteroides LVBH107 survived at acid, bile salts, lysozyme, and hydrogen peroxide conditions, auto-aggregated and co-aggregated with P. gingivalis, exhibited strong hydrophobicity and electrostatic action, and strongly adhered to gingival epithelial and HT-29 cells (thus exhibiting oral tissue adherence and colonization abilities). Moreover, L.mesenteroides LVBH107 exhibited sensitivity to antibiotics erythromycin, doxycycline, minocycline, ampicillin, and others (thus indicating it lacked antibiotic resistance plasmids), effectively inhibited P.gingivalis biofilm formation and inflammation (in vitro inflammation model), reduced the secretion of pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) and inflammatory mediators (NO and PGE₂), and decreased the expression levels of inflammation related genes. Thus, L.mesenterica LVBH107 holds promise as a probiotic that can inhibit P.gingivalis biofilm formation and exert anti-inflammatory activity to maintain oral health.

Isolation and characterization of exopolysaccharide derived from Lacticaseibacillus paracasei AS20(1) with probiotic potential and evaluation of its antibacterial activity

This study was done to find exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) against foodborne pathogens. Isolated LAB were screened to find the ones with the ability to produce antibacterial EPS against foodborne pathogens. Among tested EPSs, EPS of AS20(1) isolate showed inhibitory effects on the growth of Listeria monocytogenes (MIC = 0·935 mg ml^-1 , MBC = 0·935 mg ml^-1 ), Yersinia enterocolitica (MIC = 12·5 mg ml^-1 , MBC = 50 mg ml^-1 ) and Bacillus cereus (MIC = 6·25 mg ml^-1 , MBC = 12·5 mg ml^-1 ). According to 16S rRNA sequencing, AS20(1) showed the closest similarity to Lacticaseibacillus paracasei (100%). This antibacterial EPS showed negligible toxicity (4·4%-5·2%) against red blood cells. Lacticaseibacillus paracasei AS20(1) showed probiotic properties, including high acid resistance, hydrophobicity (47·5%), autoaggregation and coaggregation with foodborne pathogens. Also, L. paracasei AS20(1) showed no haemolysis activity and antibiotic resistance. Characterization of antibacterial EPS revealed that it is a heteropolysaccharide with various functional groups, amorphous structure, and smooth surface, sheet and compact structure, which can be suitable for food packaging. L. paracasei AS20(1) and its antimicrobial EPS can be used to make functional food.

Antibacterial and Antibiofilm Effect of Cell-Free Supernatant of Lactobacillus brevis KCCM 202399 Isolated from Korean Fermented Food against Streptococcus mutans KCTC 5458

This study aims to determine the antibiofilm effect of cell-free supernatant (CFS) of Lactobacillus brevis strains against Streptococcus mutans strains. To study the antibiofilm mechanism against S. mutans strains, antibacterial effects, cell surface properties (auto-aggregation and cell surface hydrophobicity), exopolysaccharide (EPS) production, and morphological changes were examined. The antibiofilm effect of L. brevis KCCM 202399 CFS as morphological changes were evaluated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), compared with the control treatment. Among the L. brevis strains, L. brevis KCCM 202399 showed the highest antibiofilm effect on S. mutans KCTC 5458. The antibacterial effect of L. brevis KCCM 202399 against S. mutans KCTC 5458 was investigated using the deferred method (16.00 mm). The minimum inhibitory concentration of L. brevis KCCM 202399 against S. mutans KCTC 5458 was 25.00%. Compared with the control treatment, L. brevis KCCM 202399 CFS inhibited the bacterial adhesion of S. mutans KCTC 5458 by decreasing auto-aggregation, cell surface hydrophobicity, and EPS production (45.91%, 40.51%, and 67.44%, respectively). L. brevis KCCM 202399 CFS inhibited and eradicated the S. mutans KCTC 5458 biofilm. Therefore, these results suggest that L. brevis KCCM 202399 CFS may be used to develop oral health in the probiotic industry.

Screening of gamma-aminobutyric acid-producing lactic acid bacteria and the characteristic of glutamate decarboxylase from Levilactobacillus brevis F109-MD3 isolated from kimchi

AIMS

This study aimed to screen the γ-aminobutyric acid (GABA)-producing lactic acid bacteria (LAB) from kimchi, and investigate the glutamate decarboxylase (GAD) activity of the highest GABA-producing strain.

METHODS AND RESULTS

Seven strains of LAB were screened from kimchi with GABA-producing activity. Strain Levilactobacillus brevis F109-MD3 showed the highest GABA-producing ability. It produced GABA at a concentration of 520 mmol l^-1 with a 97.4% GABA conversion rate in MRS broth containing 10% monosodium glutamate for 72 h. The addition of pyridoxal 5'-phosphate had no significant effect on the GAD activity of L. brevis F109-MD3. The optimal pH range of GAD was 3.0-5.0 and the optimal temperature was 65°C. The D value of GAD at 50, 60 and 70°C was 7143, 971 and 124 min respectively and Z value was 11.36°C.

CONCLUSIONS

Seven strains isolated from kimchi, especially F109-MD3, showed high GABA-production ability even in the high concentrations of MSG at 7.5% and 10%. The GAD activity showed an effective broad pH range and higher optimal temperature.

SIGNIFICANCE AND IMPACT OF THE STUDY

These seven strains could be potentially useful for food-grade GABA production and the development of healthy foods.

Characterization of Macro- and Microalgae Extracts Bioactive Compounds and Micro- and Macroelements Transition from Algae to Extract

The aim of this study was to evaluate the characteristics of macroalgae (Cladophora rupestris, Furcellaria lumbricalis, Ulva intestinalis) and microalgae (Arthrospira platensis (Sp1, Sp2), Chlorella vulgaris) extracts, including micro- and macroelement transition to extract, antioxidant, antimicrobial properties, the concentrations of chlorophyll (-a, -b), and the total carotenoid concentration (TCC). In macroalgae, the highest TCC and chlorophyll content were found in C. rupestris. In microalgae, the TCC was 10.1-times higher in C. vulgaris than in Sp1, Sp2; however, the chlorophyll contents in C. vulgaris samples were lower. A moderate negative correlation was found between the chlorophyll-a and TCC contents (r = -0.4644). In macroalgae extract samples, C. rupestris and F. lumbricalis showed the highest total phenolic compound content (TPCC). DPPH antioxidant activity and TPCC in microalgae was related to the TCC (r = 0.6191, r = 0.6439, respectively). Sp2 extracts inhibited Staphylococcus haemolyticus; C. rupestris, F. lumbricalis, U. intestinalis, and Sp2 extracts inhibited Bacillus subtilis; and U. intestinalis extracts inhibited Streptococcus mutans strains. This study showed that extraction is a suitable technology for toxic metal decontamination in algae; however, some of the desirable microelements are reduced during the extraction, and only the final products, could be applied in food, feed, and others.

Inhibitory effects of Lactobacillus brevis KU15153 against Streptococcus mutans KCTC 5316 causing dental caries

This study determined the inhibitory effect of Lactobacillus brevis KU15153 against cariogenic Streptococcus mutans KCTC 5316. Antimicrobial activity, auto-aggregation, cell surface hydrophobicity, exopolysaccharides (EPS) production, biofilm formation, and morphological changes were assessed in the presence of L. brevis KU15153. L. brevis KU15153 exhibited the highest antimicrobial activity against S. mutans KCTC 5316 (28.67 ± 4.16 mm). Auto-aggregation (38.32%), cell surface hydrophobicity (27.08%), and EPS production rate (58.52%) of S. mutans KCTC 5316 slightly decreased upon treatment with L. brevis KU15153. Additionally, crystal violet stanning and scanning electron microscopy confirmed the L. brevis KU15153-mediated inhibition of biofilm formation by S. mutans KCTC 5316 in comparison to that observed in the negative control (untreated S. mutans KCTC 5316). These results indicate that the L. brevis KU15153 could be used as a potential probiotic for maintaining oral health.

Isolation and functional characterization of exopolysaccharide produced by Lactobacillus plantarum S123 isolated from traditional Chinese cheese

During the past few years, there are growing interests in the potential use of exopolysaccharide (EPS) in the food industry as an efficient biopolymer because of its exceptional biological features. Therefore, the aim of the present study is EPS production by Lactobacillus Plantarum S123 (S123 EPS), its partial structural and biopotential characterization. The results from this study suggested that the major portion of S123 EPS has an amorphous sponge-like structure with partial crystalline nature. The FTIR and NMR results suggested that the S123 EPS consists of carbonyl and hydroxyl groups, respectively. Furthermore, the results of technological as well as biotechnological characterization suggested that the S123 EPS was exhibited excellent antibacterial activity against Gram-positive (7.2 mm) and Gram-negative bacteria (11.5 mm), DPPH radical scavenging activity (> 65%), water holding capacity (326.6 ± 0.5%), oil holding capacity (995.3 ± 0.2%), flocculation (89.5 ± 0.6%), and emulsifying (80.1 ± 1.1%) activities. Overall, the present results suggested that due to the highly porous structure and efficient biotechnological potential, S123 EPS from Lactobacillus plantarum S123 (L. plantarum S123) can be used in the functional food product.

Potential neuroprotective effects of heat-killed Lactococcus lactis KC24 using SH-SY5Y cells against oxidative stress induced by hydrogen peroxide

The present study was an investigation of the neuroprotective effects of probiotic bacteria in SH-SY5Y neuroblastoma cells experiencing oxidative stress. The bacterial strains were: commercial Lactobacillus rhamnosus GG; two isolated bacterial strains (Lactobacillus delbrueckii KU200170 and Lactobacillus plantarum KU200661); and probiotic Lactococcus lactis KC24. To evaluate the neuroprotective effects of the bacteria, a conditioned medium (CM) was prepared using HT-29 cells cultured with the heat-killed probiotic strains. Of the bacterial strains tested, the oxidatively stressed SH-SY5Y cells were most viable when cultured with L. lactis KC24-CM. L. lactis KC24-CM promoted the expression of brain-derived neurotropic factor (BDNF) in the HT-29 cells. It also significantly increased BDNF expression and reduced the apoptosis-related Bax/Bcl-2 ratio in the oxidatively stressed SH-SY5Y cells. Therefore, L. lactis KC24 is a potential psychobiotic for use in the functional food industry.

Fermented dairy products as delivery vehicles of novel probiotic strains isolated from traditional fermented Asian foods

The screening of novel probiotic strains from various food sources including fruits, vegetables, herbs, and traditional fermented foods, have been of growing concern recently. Most of these potential probiotic lactic acid bacteria isolates were distinguished from the commercial probiotics based on multiple therapeutic effects and functionalities. Recent in vitro and in vivo investigates have also verified the usage of probiotics to lower the risk of diseases. Application of these novel strains in fermented dairy products is also an emerging trend to improve the physical and quality characteristics, functional properties, and safety of dairy products. Moreover, since dairy products are one of the highest consumed products in the globe, the dispatch channels for fermented dairy products are already established. Therefore, incorporating novel probiotic strains into fermented dairy products might be the most feasible approach for their delivery. In this context, our aim is to discuss the feasibility of dairy products as delivery vehicles for novel probiotic strains. Thus, we summarize the scientific evidence that points to a dynamic future for the production of fermented dairy-based probiotics.

Probiotic and Antioxidant Potential of Lactobacillus reuteriLR12 and Lactobacillus lactisLL10 Isolated from Pineapple Puree and Quality Analysis of Pineapple-Flavored Goat Milk Yoghurt during Storage

In recent years, studies have focused on the therapeutic properties of probiotics to eliminate pathogenic microorganisms associated with various diseases. Lactobacilli are important probiotics groups that have been found to possess many health-promoting activities. This study was carried out to isolate LactobacillusreuteriLR12 and L. lactisLL10 from pineapple puree. The invitro analysis to evaluate probiotic characteristics of the isolated bacteria included survival in bile and acid tolerance. The cell-free supernatant of L. reuteri LR12 was effective against various pathogenic bacteria and fungi compared with L. lactisLL10. These two bacterial strains have strong anti-biofilm activity (100%) against Enterococcus faecalis, Staphylococcus aureus, and Bacillus cereus. The bacterial strains exhibited adhesion properties to HT-29 cells (human colorectal adenocarcinoma). These bacteria showed DPPH- (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free radical scavenging activity, scavenging of hydroxyl radical activity, superoxide radical scavenging activity, and reducing power activity in the range of 72% ± 3%to 89.3% ± 1.7%, 64% ± 2.7%to 66.8% ± 1.5%, 59.8% ± 4.1% to 63.8% ± 2.1%, and 60.4% ± 1.8%to 66.1% ± 3.3%, respectively. Pineapple puree was used as the starter culture with milk for 2 days for yogurt preparation. Pineapple puree increased flavor and showed the physicochemical properties of yogurt. The finding of the sensory evaluation revealed no significant change compared with the control, except the appearance of yogurt. These findings show that Lactobacilli and pineapple puree have potential use in various probiotic preparations for the fermentation industry.