Tested Lactic Acid Bacteria Strains Research Articles

Antagonistic activity of lactic acid bacteria isolated from Minas artisanal cheeses against Brucella abortus

This study aimed to evaluate methods for studying the in vitro antimicrobial activity of lactic acid bacteria (LAB) against Brucella abortus and to evaluate the antagonistic effect of LAB on the viability of this pathogen. A total of 18 LAB strains (Lactobacillus plantarum, n = 11; Pediococcus acidilactici, n = 1; Lactobacillus rhamnosus, n = 4; and Lactobacillus brevis, n = 2), isolated from Minas artisanal cheeses produced in three regions (Canastra, Campos das Vertentes, and Araxá) of Minas Gerais State, Brazil, were tested for their antimicrobial activity against B. abortus using three methods: spot-on-lawn, agar well diffusion assay, and antagonistic activity of the culture supernatants. None of the tested LAB strains could inhibit B. abortus in the spot-on-lawn and agar-well diffusion assays. The supernatants produced by LAB had an acidic pH, with intensity depending on bacterial growth and strain, and could inhibit the growth of B. abortus. In contrast, pH-neutralized (pH 7.0) LAB supernatants did not suppress the growth of B. abortus. The results showed that the best technique to study the in vitro antagonism of LAB against B. abortus was the antagonistic activity of culture supernatants. The growth of B. abortus may have been inhibited by acid production.

Influence of different lactic acid bacteria strains and milling process on the solid-state fermented green and red lentils (Lens culinaris L.) properties including gamma-aminobutyric acid formation.

The aim of this study was to evaluate the influence of lactic acid bacteria (LAB) strains (Lactiplantibacillus plantarum No.122 and Lacticaseibacillus casei No.210) and milling process on the solid-state fermented (for 24 h, at 30°C) green and red lentils (Lens culinaris L.) properties, chiefly pH, LAB viable counts, color coordinates, free amino acid (FAA) profile, γ-aminobutyric acid (GABA) and biogenic amine (BA) concentrations, fatty acid (FA) and volatile compound (VC) profiles. Results showed that both of the tested LAB strains are suitable for the fermentation of lentils: pH of fermented lentils was <4.5 and LAB viable counts >8.0 log10 colony-forming units (CFU)/g. A very strong negative correlation was found (r = -0.973, p ≤ 0.0001) between LAB counts and pH of the samples. Also, fermentation and milling process were significant factors toward color coordinates of the lentils. In most of the cases, solid-state fermentation (SSF) increased essential FAA content in lentils; however, some of the non-essential FAA content was reduced. SSF significantly increased GABA concentration in lentils and milling process was a significant factor on GABA content of the samples (p ≤ 0.05). The main BA in lentils was spermidine, and SSF decreased their total BA content (34.8% on average in red lentils and 39.9% on average in green lentils). The main FA in lentils were linoleic and oleic. The main VC in lentils were hexanal, 1-hexanol, hexanoic acid, D-limonene and (E)-2-nonen-1-ol. Furthermore, most of the VC showed significant correlations with pH of lentil samples, LAB counts and FA content. Finally, the LAB strain used for fermentation and the milling process of lentils are significant factors for most of the analyzed parameters in lentil. Moreover, despite the higher GABA concentration found in green non-milled SSF lentils, application of combined milling and SSF is recommended because they showed the lowest BA content in addition to higher essential FAA and GABA concentrations.

Characterization and Protective Properties of Lactic Acid Bacteria Intended to Be Used in Probiotic Preparation for Honeybees (Apis mellifera L.)-An In Vitro Study.

Lactic acid bacteria (LAB) are widely used probiotics and offer promising prospects for increasing the viability of honeybees. Thus, the probiotic potential of 10 LAB strains was determined, which in our previous studies showed the most potent protective abilities. In the current study, we investigated various properties of probiotic candidates. The tested LAB strains varied in susceptibility to tested antibiotics. Isolates showed high viability in sugar syrups and gastrointestinal conditions. None of the LAB strains exhibited β-hemolytic activity, mutual antagonism, mucin degradation, hydrogen peroxide production capacity, or bile salt hydrolase (BSH) activity. Additionally, the cytotoxicity of LAB cell-free supernatants (CFS) was assessed, as well as the effect of CFS from P. pentosaceus 14/1 on the cytotoxicity of coumaphos and chlorpyrifos in the Caco-2 cell line. The viability of Caco-2 cells reached up to 89.81% in the presence of the highest concentration of CFS. Furthermore, LAB metabolites decreased the cytotoxicity of insecticides (up to 19.32%) thus demonstrating cytoprotective activity. All tested LAB strains produced lactic, acetic, and malonic acids. This research allowed the selection of the most effective LAB strains, in terms of probiosis, for future in vivo studies aimed at developing an ecologically protective biopreparation for honeybees.

In vitro detoxification of aflatoxin B1 and ochratoxin A by lactic acid bacteria isolated from Algerian fermented foods

Wheat occupies the first place in Algerian’s diet. However, because of the risk of mycotoxin contamination, its consumption can cause serious health concern to Algerian population. This study aimed to determine the in vitro detoxification properties of lactic acid bacteria (LAB) strains toward aflatoxin B1 (AFB1) and ochratoxin A (OTA), the most prevalent mycotoxins in wheat and derived products in Algeria. Eleven LAB strains isolated from Algerian fermented foods were characterized and identified using API 50 CHL and 16S rDNA sequencing methods. In order to study the ability of LAB strains to remove AFB1 and OTA, viable and heat inactivated cells of two LAB strains (Lab-L4/al and Lab-L1) selected among the eleven isolated and identified ones, as well as of the reference strain Lactobacillus plantarum (LP) R1096 were incubated individually in Citrate Phosphate Buffer (CPB 0.1 M, pH 6 or 5) containing AFB1 and/or OTA at a concentration each of 40 ng/mL for 24 h at 25 °C. Free mycotoxin concentrations were analyzed by HPLC-FLD. The isolated LAB strains were identified as Lactococcus lactis ssp lactis 1, Lactococcus lactis ssp lactis 2 and Lactobacillus paracasei ssp paracasei using API 50 CHL kit, whereas with the molecular method, the strains were identified as Enterococcus faecium and Enterococcus durans. Both viable and nonviable cells of Lab-L4/al and Lab-L1, as well as LP R1096, were able to remove AFB1 and OTA, with efficiency varying between the strains and higher for AFB1 with nonviable cells (>50 %). Removal ability of viable Lab-L4/al and LP R1096 cells increased with a decrease in pH from 6 to 5, while pH had no effect on the amounts of mycotoxins removed by viable Lab-L1 cells. In conclusion, the tested LAB strains were able to reduce the amounts of AFB1 and OTA in vitro conditions. This result suggests that these LAB strains could be used as additives or formative agents to reduce mycotoxin levels in fermented wheat foods such as sourdough bread.

Characterisation of Lacto-Fermented Cricket (Acheta domesticus) Flour and Its Influence on the Quality Parameters and Acrylamide Formation in Wheat Biscuits

The aim of this study was to evaluate the influence of different amounts (40, 80 and 100 g) of non-fermented and fermented (with Lactiplantibacillus plantarum No. 122 and Lacticaseibacillus casei No. 210) cricket flour (Cr) on the quality characteristics and acrylamide formation in wheat biscuits (WB). The main formula for WB preparation consisted of 280 g of wheat flour, 100 g of margarine, 50 g of saccharose, 3 g of vanilla sugar, 50 g of eggs, 1.5 g of salt and 2.0 g of baking powder. It was established that the highest lactic acid bacteria (LAB) number was achieved in 48 h with No. 122 fermented Cr (11.8 log10 CFU/g) and the lowest pH (4.34) was obtained after 48 h of Cr fermentation with both the tested LAB strains. The total colour differences were in the range of 17.54 to 22.08 and, in every case, fermented samples were clearly distinguished from untreated ones. Fermentation increased tyramine content in Cr (from 13.0 to 29.2 times). The main FAs in Cr were palmitic acid, stearic acid, octadec-9-enoic acid and linoleic acid. The lowest acrylamide content (84.1 µg/kg) was found in WB with 40 g of Cr fermented with No. 210. Significant differences in WB overall acceptability were not found. However, the highest intensity of emotion “happy” was elicited by WB with 80 g of Cr fermented with No. 122. Due to the demonstrated decrease of acrylamide content, fermented Cr can be considered a beneficial ingredient for the manufacture of WB.

Biodegradation of Punicalagin into Ellagic Acid by Selected Probiotic Bacteria: A Study of the Underlying Mechanisms by MS-Based Proteomics.

Pomegranate (Punica granatum L.) is a well-known source of bioactive phenolic compounds such as ellagitannins, anthocyanins, and flavanols. Punicalagin, one of the main constituents of pomegranate, needs to be biodegraded by bacteria to yield metabolites of medicinal interest. In this work, we tested 30 lactic acid bacteria (LAB) and their capacity to transform punicalagin from a punicalagin-rich pomegranate extract into smaller bioactive molecules, namely, ellagic acid and urolithins. These were identified and quantified by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS2). Further, we evaluated the molecular mechanism governing this transformation through label-free comparative MS-based proteomics. All tested LAB strains were capable of transforming punicalagin into ellagic acid, while the biosynthesis of urolithins was not observed. Proteomic analysis revealed an increase of generic transglycosylases that might have a hydrolytic role in the target phenolic molecule, coupled with an increase in the quantity of ATP-binding cassette (ABC) transporters, which might play a relevant role in transporting the resulting byproducts in and out of the cell.

Honeybee-associated lactic acid bacteria and their probiotic potential for human use.

This study aims to identify lactic acid bacteria (LAB) isolated from honeybees (Apis mellifera workers and larvae) in detail and to determine their functional probiotic properties. A total of 11 strains were classified based on morphological and biochemical characteristics. Preliminary probiotic properties of strains, that were molecularly identified using 16S rRNA, such as antimicrobial activity, tolerance to digestive conditions, aggregation ability, were investigated. The antimicrobial properties of strains were tested against a wide range of human pathogens. All strains that showed γ-hemolysis and did not contain bacteriophages were considered safe. The strains' survivability checked for 0.3% bile and 3.0-7.8 pH contents was promising. The highest autoaggregation ranged from 14.7 to 30.76% after 4h. Tested LAB strains markedly exhibited coaggregation with Listeria monocytogenes and Escherichia coli. According to the results, tested bacteria showed significant antagonistic effects against pathogens, and positive probiotic characteristics compatible with in vitro gastrointestinal tract conditions. The results suggest that Apis mellifera LAB symbionts may have a probiotic potential, and be effective and safe candidates for human use. This study provides an addition to the development of the current knowledge by defining in detail honeybee-associated bacteria and determining their probiotic potential.

Novel Probiotic Lactic Acid Bacteria with In Vitro Bioremediation Potential of Toxic Lead and Cadmium.

In this study, newly isolated lactic acid bacteria (LAB) were screened for the potential bioremediation capacity against toxic lead (Pb, II) and cadmium (Cd, II) with their bioaccessibility and survivability. Five strains were selected from eighteen previously isolated probiotic LAB strains based on heavy metal-resistant potentiality through in vitro disc-diffusion assay. These five strains were evaluated in vitro to explore the Pb and Cd binding and removal efficiencies using Flame Atomic Absorption Spectrophotometry. At the same time, their bioaccessibility and survivability were assessed in a dynamic in vitro gastrointestinal digestion model. The results revealed that all the tested strains were shown to have a high magnitude of minimum inhibitory concentration values ranging from 500 to 2000mg/L with 5 to 25mm growth inhibition zones. The results also demonstrated a significant (P < 0.05) removal of Pb and Cd among five tested LAB strains. Lactobacillus delbrueckii subsp. bulgaricus LDMB02 showed the highest removal rates of Pb and Cd. It was also revealed that these strains significantly reduced Pb and Cd bioaccessibility from 42 to 50% and 40 to 58%, respectively. Moreover, these strains were shown to have significant survivability against Pb and Cd, ranging from 80.1 to 85.4% and 81.5 to 87.5%, respectively. This study recommends the immense potential exploit of LAB as a probiotic to protect human health from the adverse effects of Pb and Cd toxicity.

Context-dependent differences in the functional responses of Lactobacillaceae strains to fermentable sugars.

Lactobacillaceae are Gram-positive rods, facultative anaerobes, and belong to the lactic acid bacteria (LAB) that frequently serve as probiotics. We systematically compared five LAB strains for the effects of different carbohydrates on their free-living and biofilm lifestyles. We found that fermentable sugars triggered an altered carrying capacity with strain specificity during planktonic growth. In addition, heterogeneous response to fermentable sugar was manifested in microbial aggregation (measured by imaging flow cytometry), colony development, and attachment to mucin. The acid production capacities of the strains were compatible and could not account for heterogeneity in their differential carrying capacity in liquid and on a solid medium. Among tested LAB strains, L. paracasei, and L. rhamnosus GG survived self-imposed acid stress while L. acidophilus was extremely sensitive to its own glucose utilization acidic products. The addition of a buffering system during growth on a solid medium significantly improved the survival of most tested probiotic strains during fermentation, but the formation of biofilms and aggregation capacity were responsive to the carbohydrate provided rather than to the acidity. We suggest that the optimal performance of the beneficial microbiota members belonging to Lactobacillaceae varies as a function of the growth model and the dependency on a buffering system.

Screening of isolated potential probiotic lactic acid bacteria from Sichuan pickle for cholesterol lowering property and triglycerides lowering activity

The aim of this study was to isolate lactic acid bacteria (LAB) from Sichuan pickle and to assess their probiotic potential. Total of 66 LAB were isolated from 2 types of Sichuan pickle based on their morphological, physiological, biochemical, and genotypic characteristics. Then, 6 strains (BH6, BH9, BH18, BH46, BH48, BH59) were selected as candidates for further studies. The in vitro experiment showed that the cholesterol degradation rate of 4 strains BH6, BH9, BH59 exceeded 60%. And the triglyceride degradation rate of 3 strains BH6, BH9, BH18 was more than 17%. Out of 6 tested LAB strains, most of them (BH6, BH9, BH18, BH48, BH59) exhibited moderate to high survivability (59%-90%) under high concentration of bile salt (3%) and their survival rate was 72%-95% (BH6,BH18,BH46,BH48,BH59) at low pH conditions. The in vitro experiment showed that all LAB strains inhibited the growth of tested pathogenic microorganisms. Based on the results of presently in vitro experiments, it was concluded that the BH6 isolate had better cholesterol lowering ability (65.36%), triglyceride degradation ability (18.97%), bile salt tolerance and bacteriostatic ability. The potential LAB strain, BH6 was identified as Lactobacillus plantarum by 16S rRNA sequencing. In conclusion, the strain BH6 screened from Sichuan pickle had good ability to degrade cholesterol and triglyceride; and it had better tolerance to acid and bile salt; which also had good bacteriostatic ability. Therefor the strain BH6 has the potential to be used as edible probiotics.

Assessment of biogenic amine production by lactic acid bacteria isolated from Serbian traditionally fermented foods

The aim of this study was to monitor the production of biogenic amines by 156 selected lactic acid bacteria (LAB) strains isolated from Serbian traditionally fermented sausages and cheeses. The method for the determination of biogenic amines is liquid chromatography tandem mass spectrometry (LC-MS/MS). The measured concentrations of putrescine, cadaverine, tryptamine and spermidine (except in 13 LAB strains) were below the detection limit of the analytical method (0.1 mg/L), whereas those of histamine, tyramine and spermine were above the limit of detection, but still not significant. Tyramine was the only amine that had a measured concentration of 59.89 ± 0.06 mg L-1. Most of the tested LAB strains produced tyramine in broth below 26 mg L-1 with the exception of Enterococcus faecalis strains (59.89 ± 6.66 mg L-1) and Enterococcus faecium strains (47.33 ± 8.58 mg L-1). The low concentrations of biogenic amines are considered non-significant from both a technological and safety point of view.

Isolation and characterization of dominant lactic acid bacteria from raw goat milk: Assessment of probiotic potential and technological properties

The objective of this study was to isolate and characterize Lactic Acid Bacteria (LAB) from raw goat milk, and to evaluate their probiotic attributes, technological properties and safety profiles. A total of 50 LAB strains were isolated and identified from 18 goat milk samples based on their morphological, physiological, biochemical, and genotypic characteristics. We found the existence of 6 genera where Lactobacillus was found as dominant (50 %). The in-vitro experiment showed that more than 80 % of the representative LAB strains inhibited the growth of tested pathogenic microorganisms. Out of 11 tested LAB strains, most of them exhibited moderate to high survivability (80–100 %) under intestinal juice, pancreatic juice and bile salt, and which was 70–80 % at low pH conditions. All tested LAB strains produced diacetyl, and 73 % of the tested strains showed proteolytic activity whereas only 27 % strains exhibited weak lipolysis. In case of antibiotic susceptibility, most of the LAB strains exhibited resistance against the tested antibiotics. All LAB strains produced exopolysaccharide to a variable extent ranging from 20 to 93 mg/L where the Lactobacillus delbrueckii subsp. bulgaricus being the greatest producer. The in-vitro experiments regarding safety profile showed that all the isolated LAB strains were found as non-virulence. Furthermore, our lab-scale fermentation study demonstrated that most isolated LAB strains possess the starter culture properties for producing firm milk curd. In conclusion, this study revealed that the isolated LAB strains from raw goat milk retain the potential to be used in fermented foods because of their safety aspects, probiotic attributes, and technological characteristics.

Biotransformation of Flavonoids by Newly Isolated and Characterized Lactobacillus pentosus NGI01 Strain from Kimchi.

Lactic acid bacteria (LAB) are generally recognized as safe (GRAS) microorganisms. This study aimed to identify novel LAB strains that can transform flavonoids into aglycones to improve bioavailability. We isolated 34 LAB strains from kimchi. The biotransformation activity of these 34 LAB strains was investigated based on α-L-rhamnosidase and β-D-glucosidase activities. Among them, 10 LAB strains with high activities were identified by 16S rRNA sequencing analysis. All tested LAB strains converted hesperidin to hesperetin (12.5–30.3%). Of these, only the Lactobacillus pentosus NGI01 strain produced quercetin from rutin (3.9%). The optimal biotransformation conditions for the L. pentosus NGI01 producing hesperetin and quercetin were investigated. The highest final product concentrations of hesperetin and quercetin were 207 and 78 μM, respectively. Thus, the L. pentosus NGI01 strain can be a biocatalyst for producing flavonoid aglycones in the chemical and food industries.

Screening of Lactic Acid Bacteria for the Bio-Control of Botrytis cinerea and the Potential of Lactiplantibacillus plantarum for Eco-Friendly Preservation of Fresh-Cut Kiwifruit.

Botrytis cinerea, responsible for grey mold, represents the first biological cause of fruit and vegetable spoilage phenomena in post-harvest. Kiwifruit is a climacteric fruit particularly prone to this mold infestation during storage. Lactic acid bacteria (LAB) are food-grade bacteria that can synthesize several metabolites with antimicrobial activity and are, therefore, suggested as promising and eco-friendly resources for the bio-control of molds on fruits and vegetables. In this work, we propose the screening of a collection of 300 LAB previously isolated from traditional sourdoughs for their ability to counteract in vitro the growth of Botrytis cinerea CECT 20973. Only 2% of tested LAB strains belonging to Lactiplantibacillus plantarum species, exerted a strong antagonism against B. cinerea. The cell-free supernatants were partially characterized and results clearly indicated that high levels of lactic acid contributed to the antagonistic activity. PAN01 and UFG 121 cell-free supernatants were investigated as potential bio-control agents in a preliminary in vivo assay using freshly cut kiwifruits as a food model. The application of cell-free supernatants allowed to delay the growth of B. cinerea on artificially contaminated kiwifruits until two weeks. The antagonistic activity was greatly affected by the storage temperature (25 °C and 4 °C) selected for the processed fruits, suggesting the importance to include microbial-based solution in a broader framework of hurdle technologies.

Effects of Lacto-Fermented Agricultural By-Products as a Natural Disinfectant against Post-Harvest Diseases of Mango (Mangifera indica L.).

Background: the antagonism activity of lactic acid bacteria metabolites has the potential to prevent fungal growth on mango. Methods: the potential of developing natural disinfectant while using watermelon rinds (WR), pineapple (PP), orange peels (OP), palm kernel cake (PKC), and rice bran (RB), via lacto-fermentation was investigated. The obtained lactic acid bacteria (LAB) metabolites were then employed and the in vitro antifungal activity toward five spoilage fungi of mango was tested through liquid and solid systems. Besides, the effect of the produced disinfectant on the fungal growth inhibition and quality of mango was investigated. Results: the strains Lactobacillus plantarum ATCC8014 and Lactobacillus fermentum ATCC9338 growing in the substrates PKC and PP exhibited significantly higher in vitro antifungal activity against Colletotrichum gloeosporioides and Botryodiplodia theobromae as compared to other tested LAB strains and substrates. The in-situ results demonstrated that mango samples that were treated with the disinfectant produced from PKC fermented with L. plantarum and L. fermentum had the lowest disease incidence and disease severity index after 16 days shelf life, as well as the lowest conidial concentration. Furthermore, PKC that was fermented by L. fermentum highly maintained the quality of the mango. Conclusions: lactic acid fermentation of PKC by L. fermentum demonstrated a high potential for use as a natural disinfectant to control C. gloeosporioides and B. theobromae on mango.

Isolation and Genetic Identification of Endophytic Lactic Acid Bacteria From the Amazonian Açai Fruits: Probiotics Features of Selected Strains and Their Potential to Inhibit Pathogens.

The açai palm (Euterpe oleracea) is native to the Amazon basin, a humid tropical forest. High levels of total mesophilic bacteria with high diversity have been consistently reported in açai fruits. As local consumers have few digestive problems, the results of the present study reveal the lactic acid bacteria (LAB) recovered from açai fruits with characteristics that suggest they are possible candidates for probiotics and antagonistic potential against pathogens for the first time. Açai fruits were sampled from five different locations in the Eastern Amazonia floodplains. Sixty-six isolates were recovered from fruits and tested for some probiotic characteristics following FAO/WHO guidelines. Approximately 65% of the isolates showed no catalase or oxidase activity, Gram-positive staining or cocci and bacilli cell morphology. Furthermore, 48% of the isolates demonstrated preliminary characteristics that suggest safety for use, as they presented no coagulase enzyme activity or gamma-hemolysis. These strains were identified as belonging to the genera Lactiplantibacillus and Pediococcus, and 32 strains also presented resistance to vancomycin, ciprofloxacin and streptomycin. In addition, 28 isolates showed a survival rate, expressed as log cycle reduction, higher than 0.9 under gastric conditions (pH 2). All strains tested positive in bile salts deconjugation tests and showed a survival rate higher than 0.8 in the presence of this salt. Regarding antimicrobial activity against pathogens, all strains were able to inhibit Salmonella Typhimurium (ATCC® 14028TM) and 97% were capable of inhibiting Escherichia coli (ATCC® 25922TM). Concerning the results of in vitro antagonistic assays, three isolates (B125, B135, and Z183 strains) were selected for antagonistic tests using açai juice contaminated with these two pathogens. All tested LAB strains were able to inhibit pathogen growth in açai juice. In summary, açai fruits are a potential source of LAB isolates to be investigated as probiotics.

Growth of lactic acid bacteria in milk phospholipids enhances their adhesion to Caco-2 cells

The mechanisms of bacterial adhesion to human cells involve several complex reactions and activation of genes and proteins. It has been reported that the food components in dairy matrices, such as sugar or salt, can decrease bacterial adhesion to Caco-2 cells. However, it has not been evaluated whether the bacteria grown in media supplemented with milk phospholipids (MPL) can increase or decrease the adhesion of these cells. The objective of this work was to evaluate the effects of MPL on the kinetic growth of lactic acid bacteria (LAB) and their functional characteristics as probiotics, expression of surface protein genes, and adherence to Caco-2 cells. Seven LAB strains isolated from various dairy products were characterized. Five of the tested LAB strains were able to grow in a chemically defined medium supplemented with MPL. Lactobacillus reuteri OSU-PECh-48 showed the highest growth rate and the greatest optical density. All of the strains tested showed tolerance to acidic conditions at pH 3.0 and to bile salts at 0.5 and 1% concentrations. Auto-aggregation and cell surface hydrophobicity ability were evaluated, with nonsignificant differences between the strains grown in MPL and without MPL. Gene expression of 6 surface proteins was evaluated in the presence or absence of MPL. Pediococcus acidilactici OSU-PECh-L and OSU-PECh-48 were the strains with highest relative expression of 5 of the 6 genes evaluated. Lactobacillus paracasei OSU-PECh-BA was the strain with the lowest level of expression of surface protein genes. Most of the bacteria tested had increased adhesion to Caco-2 cells after growth in MPL. The bacteria with the highest degrees of adhesion observed were Lactobacillus paracasei OSU-PECh-3B, Pediococcus acidilactici OSU-PECh-L, and Lactobacillus reuteri OSU-PECh-48. The genes Cnb and EF-Tu increased in expression in the presence of MPL in most of the LAB tested. The results obtained in this work demonstrate the high potential of these LAB strains for use as starters or beneficial cultures in fermentation of not only dairy products but also other food fermentation processes, with promising ability to increase residence time in the gut, modify the microbiome, and improve human health.

Technological and probiotic potential of autochthonous lactic acid bacteria from spontaneously fermented dromedary milk

This work aimed to identify autochthonous lactic acid bacteria (LAB) from spontaneously fermented dromedary milk and explore their technological and probiotic properties in vitro. Analysis of the strains by 16S rDNA gene sequencing revealed four strains as Enterococcus faecalis, one strain as Enterococcus faecium, one strain as Lactococcus lactis, and four strains as Streptococcus pasteurianus. However, two strains (LEFS 42 and LEFS 55) showed a low 16S similarity (97.60% and 97.54%, respectively) with the type strain Streptococcus suis 92-2742T. All the tested LAB strains possessed acidifying and proteolytic capacities. Most of them were lipolytic (83.33%) and had the ability to produce exopolysaccharides (91.67%). All the studied LAB strains were non-hemolytic and exhibited antibacterial activity and sensitivity toward five antibiotics. Streptococcus sp. LEFS 55 had the highest hydrophobicity, autoaggregation, and coaggregation abilities. Moreover, all the isolated strains were able to resist simulated human gastrointestinal tract conditions and scavenge DPPH and ABTS radicals. Practical applications Nutritional and medicinal values of dromedary milk can be further increased after fermentation. Commercially available starter cultures are from bovine-based dairy industry being not competitive with endogenous microbiota of dromedary milk, which might not give a desirable final product. However, to date, few attempts have been performed to isolate and characterize lactic acid bacteria from spontaneously fermented dromedary milk. Besides, the probiotic potential of autochthonous lactic acid bacteria from fermented dromedary milk remains unexplored. Hence, this study aimed to identify autochthonous lactic acid bacteria from spontaneously fermented dromedary milk and to investigate their technological and probiotic potential. The isolation of autochthonous lactic acid bacteria with technological and probiotic properties from dromedary milk allows the production of fermented dromedary milk with functional properties and the diversification of dromedary milk products.

Study of the antibiotic residues in poultry meat in some of the EU countries and selection of the best compositions of lactic acid bacteria and essential oils against Salmonella enterica

In this study, the presence of antibiotics (ANB) residues was evaluated in poultry meat purchased from German and Lithuanian markets. In addition, the antimicrobial activity of 13 lactic acid bacteria (LAB) strains, 2 essential oils (EO) (Thymus vulgaris and Origanum vulgare L.), and their compositions were tested for the purpose of inhibiting antibiotic-resistant Salmonella spp. ANB residues were found in 3 out of the 20 analyzed poultry meat samples: sample no. 8 contained enrofloxacin (0.46 μg/kg), sample no. 14 contained both enrofloxacin and doxycycline (0.05 and 16.8 μg/kg, respectively), and sample no. 18 contained enrofloxacin (2.06 μg/kg). The maximum residue limits (MRLs) for the sum of enrofloxacin and ciprofloxacin and for doxycycline in the poultry muscle are 100 μg/kg. Finally, none of the tested poultry meat samples exceeded the suggested MRLs; however, the issue of ANB residues still requires monitoring of the poultry industry in Germany, Poland, and Lithuania, despite the currently established low ANB concentrations. These findings can be explained by the increased use of alternatives to ANB in the poultry industry. Our results showed that an effective alternative to ANB, which can help to reduce the occurrence of antibiotic-resistant salmonella, is a composition containing 1.0% of thyme EO and the following LAB strains: Lactobacillus plantrum LUHS122, Enteroccocus pseudoavium LUHS242, Lactobacillus casei LUHS210, Lactobacillus paracasei LUHS244, Lactobacillus plantarum LUHS135, Lactobacillus coryniformins LUHS71, and Lactobacillus uvarum LUHS245, which can be recommended for poultry industry as components of feed or for the treatment of surfaces, to control the contamination with Salmonella strains. However, it should be mentioned that most of the tested LAB strains were inhibited by thyme EO at the concentrations of 0.5 and 1.0%, except for LUHS122, LUHS210, and LUHS245. Finally, it can be noted that the agents responsible for the inhibitory effect on Salmonella are not the viable LAB strains but rather their metabolites, and further studies are needed to identify which metabolites are the most important.

The effect of oral administration of lactic acid bacteria isolated from kefir on intestinal microbiota, growth performance and survival in juvenile rainbow trout, Oncorhynchus mykiss

Lactic acid bacteria (LAB) are used in the aquaculture industry to improve growth indices and nutrition efficiency of farmed fish. Kefir is a natural probiotic that largely consists of these microorganisms. This study aimed to isolate LAB strains from kefir grains and investigate their effects on the intestinal microbiota and growth indices of juvenile rainbow trout. Based on the results, one isolate was identified as Lactobacillus faraginis (LF) and other one as En terococcus durans (ED), both were gram positive, non-hemolytic, catalase and oxidase negative. Both strains showed resistance to acidic environments and gastric juice and were able to grow against bile salts i.e. the hydrophobicity potential of both strains was evaluated above 50%. The results showed that both strains had appropriate and acceptable probiotic properties. A total of 480 juvenile fish with were randomly divided into eight groups viz. Control (basal diet), LF1 and LF2 receiving diets supplemented with L. faraginis at 10 7 and 10 8 cfu/g, respectively, ED1 and ED2 diets supplemented with E. durans at 10 7 and 10 8 cfu/g, respectively, Bactocell group receiving a diet supplemented with commercial probiotic Bactocell PA-10 (10 10 cfu/g), combined treatments LF1+ED1 (5×10 6 cfu/g) and LF2+ED2 (5×10 7 cfu/g). The strains were prepared in the form of lyophilized powder and added to the basal diet as supplements. Sampling was performed after 0, 30, 15, and 45 days feeding with the diets. In the in vivo investigation, the highest LAB colony counts were obtained for the ED2, Bactocell, LF2+ED2 and LF2 groups, respectively. The highest BWI, SGR, DWG, PER, and CF, and the lowest FCR were observed in the LF2+ED2, Bactocell, ED2, and LF2 groups, respectively. On the other hand, the LF2+ED2, Bactocell and LF2 treatments also had the highest survival rate. Apparently, the use of the tested LAB strains as probiotic in high doses (LF2, ED2) and in combination (LF2+ED2) could improve growth indices, the intestinal LAB population and survival rate in juvenile rainbow trout.