Characterization of new strain Lactobacillus paracasei I-N-10 with proteolytic activity: Potential role in decrease in β-casein immuno-reactivity

The proteolytic activity of thirty-three LAB isolates from Mongolian tarag was tested on skimmed milk. The strain displaying the highest proteolytic activity was purified and presented by 16S rDNA sequencing 99.9?% homology with Lactobacillus paracasei 1-4-2A. It was named L. paracasei I-N-10. Proteases of L. paracasei I-N-10 hydrolyze predominately ??-casein and in some level ??_S2-casein; hydrolysis of ??_S1-casein was not observed. Proteolytic activity was optimal at 42?°C and neutral pH. Proteases of L. paracasei I-N-10 were inhibited by serine- and metalloproteases inhibitors. PCR amplification revealed the presence of prtP gene, which was identical to prtP gene of L. paracasei genus. Mass spectrometry analysis of ??-casein hydrolysate allowed to characterize 7 peptides resulting from proteolysis by L. paracasei I-N-10. The isolated strain was able to cleave ??-casein in different sites including 2 of the major linear epitopes implicated in its allergenicity. Being sensitive to main antibiotics classes, L. paracasei I-N-10 could be considered as safe and used as starter culture with a potential role in decreasing ??-casein immuno-reactivity.     

EVALUATION OF FUNCTIONAL ASPECTS IN LACTOBACILLUS STRAINS ISOLATED FROM DRY FERMENTED SAUSAGES

ABSTRACT

The aim of this study was to characterize lactobacilli isolated from a traditional Italian dry‐fermented sausages inoculated with Lactobacillus casei/paracasei for use as probiotics. Strains isolated were L. casei (38%), L. paracasei paracasei (32%), Lactobacillus rhamnosus (21%) and Lactobacillus sakei sakei (9%). L. paracasei paracasei and L. rhamnosus showed no significant decrease in viability compared with L. casei and L. sakei sakei in artificial gastric juice; L. casei and L. sakei sakei were not affected by artificial intestinal fluid. In human embryonic intestine cell line (INT407) in vitro model, L. rhamnosus and L. sakei sakei were more adhesive than the other strains. The production of acetic acid (40.92 ± 1.94 mmol/L) and propionic acid (0.14 ± 0.07 mmol/L) was similar in all strains tested. Considerably higher (100–250 mmol/L) levels of lactic acid were produced by L. casei, L. paracasei paracasei and L. rhamnosus, and were varied depending on microaerobic or anaerobic conditions. L. casei and L. rhamnosus had the best antibacterial activity against Escherichia coli and Salmonella enterica ssp. enterica (serovar Typhimurium). These findings suggest that L. casei and L. rhamnosus merit further investigation as novel starter cultures in meat products.

PRACTICAL APPLICATIONS

Probiotics are well established in dairy products but they are not widely used in meat products and it is expected their use in this area will expand considerably in the near future. Starter cultures of active or resting forms of microorganisms are widely employed in fermented meat products to improve sensory qualities. More recently they are being used in fermented meat products to improve the nutritional value of these products as functional foods. Probiotics in meat may exert their benefits by several methods, and more research is required to identify the strains and combinations of strains that produce the most health benefits. Our study demonstrates that the in vitro characterization of Lactobacillus strains directly isolated from dry fermented sausages can be useful to select novel starter cultures with potential probiotic characteristics among lactic acid bacteria used as commercial meat starter culture.

     

Selection of Dominant NSLAB from a Mature Traditional Cheese According to their Technological Properties and in vitro Intestinal Challenges

Abstract: Isolates (47) of lactobacilli from 5 different productions of Melichloro cheese were examined for potential use as adjunct cultures. The sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) of whole‐cell proteins classified 29 isolates as L. paraplantarum and 18 as L. paracasei subsp. paracasei. Randomly amplified polymorphic DNA‐polymerase chain reaction (RAPD‐PCR) analysis differentiated the L. paraplantarum and L. paracasei subsp. paracasei isolates at strain level and both, RAPD analysis and whole‐cell protein profiling provided useful information about the diversity of nonstarter lactic acid bacteria (NSLAB) in the different cheese productions. The isolates were slow acidifiers and about 70% of them degraded, preferentially α_s‐casein. The amounts of amino acids accumulated in the milk increased with the incubation time. A similar enzyme profile was exhibited by strains of both species, except for α‐mannosidase and α‐fucosidase, which were not detected in the L. paracasei subsp. paracasei strains. All strains grew in the presence of bile at 0.3% and the majority was able to withstand pH 2.5 and pancreatin at 0.1%. Moreover, all strains reduced cholesterol in vitro, with higher removal ability recorded for strains of L. paraplantarum. A narrow spectrum of antibacterial activity was recorded for 88% of the strains. Selected isolates with appropriate technological and interesting in vitro intestinal challenges could be used as adjuncts and deserve further studies. Practical Application: Strains selected by this study could be used as adjuncts to make the Melichloro cheese. Their contribution to cheese flavor is then going to be studied to select the most appropriate. Of course these strains have to be also studied for their probiotic potential, to say that we have a probiotic food.     

In vitro evaluation of probiotic lactic acid bacteria isolated from dairy and non-dairy environments

Four strains and 2 strains of lactic acid bacteria (LAB) were isolated from the commercial yogurt and kimchi products in Korea, respectively. Based on the 16S rRNA sequencing data, strain A from a drink-type yogurt manufactured by dairy company S, was a Gram-positive, rod-shaped Lactobacillus helveticus, and both strain B (company N) and D (company H) were identified as L. casei ssp. casei, and strain C (company L) as L. paracasei. None of yogurt strain B and D was recovered from the samples exposed to the simulated gastric juice, pH 2.0 for 1.5 hr. Of the 6 isolates tested, strain YS93 from kimchi was the most resistant to acidic condition using the simulated gastric juice, pH 2.0. Moreover, it was shown that 2 kimchi isolates and yogurt strain D produced antibacterial substances, probably bacteriocin-like peptide, which was inhibitory against Staphylococcus aureus as an indicator. In an adhesion assay using a Caco-2 cell, the adherence activity of kimchi strains YS29 and YS93 was significantly higher than those of 4 yogurt starter strains tested.     

Bacterial Proteinase Reduces Maturation Time of Dry Fermented Sausages

The effect of proteinases, from Lactobacillus paracasei subsp. paracasei NCDO151 and from Bacillus licheniformis (Alcalase, NOVO Nordisk), on the ripening of dry sausages was compared. Increased levels of starter bacteria, d-lactic acid, a sharper pH-drop and changes in chromato-graphic profiles (by gas chromatography/mass spectrometry) indicated that the enzyme from Lactobacillus paracasei accelerated the dry sausage ripening. This effect was not detected in sausages with the Alcalase enzyme. Higher sensory scores on maturity flavor, color, hardness and others, confirmed that sausages containing proteinase from L. paracasei showed the same maturity after 14 days as those without enzymes or with the Alcalase enzyme after 28 days.     

Die Mikroflora des Sauerteiges

Zusammenfassung Es wurden Ermittlungen über das Vitaminbedürfnis der an der Sauerteiggdrung beteiligten Milchsäurebakterien der UntergattungenThermobacterium, Streptobacterium andBetabacterium angestellt.Von den überprüften Sauerteigbakterien waren 54 Stämme aus sog. Reinzuchtsauerteigen und 49 Stämme aus Sauerteigen isoliert worden. Alle Sauerteigbakterien erwiesen sich biotin-, vitamin B₆-, vitamin B₁₂-, pyridoxamin- und pyridoxalautotroph. Ohne Ausnahme besteht bei den Sauerteigbakterien ein Bedürfnis an Pantothensäure und Nicotinsäure. Die Bedürftigkeit der Sauerteigbakterien an Folsäure, Vitamin B₂ und Vitamin B₁ ist von Art zu Art wechselnd.Das Vitaminbedürfnis der verschiedenen Gruppen von Sauerteigbakterien steht weitgehend in Übereinstimmung mit dem Bedürfnis der jeweils zum Vergleich herangezogenen Milchsäurebakterien definierter Art. Die Befunde geben somit eine Bestätigung der anhand des Zuckerspektrums vorgenommenen Zuordnung der Sauerteigbakterien zu den ArtenLactobacillus aeidophilus, L. casei, L. plantarum, L. fareiminis, L. brevis, L. brevis var. lindneri, L. fermentum undL. fructivorans.

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The microflora of sourdoughV. Communication: The vitamin requirement of lactic acid bacteria (Genus lactobacillus Beijerinck) of sourdough starter and sourdough

Summary Research was carried out on the vitamin requirements of lactic acid bacteria of the subgeneraThermobacterium, Streptobacterium andBetabacterium, which have a part in the sourdough fermentation. Of the investigated sourdough bacteria 54 strains were isolated from the Reinzuchtsauer (a starter culture) and 49 strains from sourdough. All sourdough bacteria were biotin-, vitamin B₆-, vitamin B₁₂-, pyridoxamine-and pyridoxal-autotroph. All sourdough bacteria showed a requirement for pantothenic acid and nicotinic acid. The requirement of sourdough bacteria for folic acid, vitamin B₂ and vitamin B₁ varied from species to species. The vitamin requirements of the different species of sourdough bacteria mostly agree with the requirements of reference strains of lactic acid bacteria (ATCC-strains, DSM-strains) with which they were compared. The results are therefore a confirmation for having assigned the sourdough bacteria from their sugar fermentation reactions to the speciesLactobacillus acidophilus, L. casei, L. plantarum, L. farciminis, L. brevis, L. fermentum, L. fructivorans andL. brevis var. lindneri.

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Nr. 4470 der Veröffentlichungen der Bundesforschungsanstalt für Getreide- und Kartoffelverarbeitung, Detmold

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Diese Untersuchungen wurden ermöglicht durch eine finanzielle Förderung seitens des Bundesministeriums für Forschung und Technologie im Rahmen des Programmes Biologie und Technik     

Synergy effects by combination with lactic acid bacteria and frutooligosaccharides on the cell growth and antimicrobial activity

The aim of this study was to identify probiotic possibility of lactic acid bacteria (LAB) from mustard leaf kimchi and investigate synergy effects of combination with LAB and fructooligosaccharide (FOS) on antimicrobial activity. Lactobacillus acidophilus GK20, L. paracasei GK74, and L. plantarum GK81 have high survival ratio under gastric and intestinal fluids and were resistant to ampicillin, streptomycin, or tetracycline. The pH of LAB gradually decreased but the titratable acidity increased owing to organic acids production. Especially, L. acidophilus GK20 and L. paracasei GK74 produced hydrogen peroxide and bacteriocin. When LAB was co-cultured with Listeria monocytogenes or Staphylococcus aureus in broth without FOS, the inhibition ratio of L. monocytogenes and S. aureus by L. acidophilus GK20 was 36 and 57%, but L. paracasei GK74 showed higher inhibitory effect against L. monocytogenes than S. aureus. Meanwhile, the cell growth, culture pH, titratable acidity, and bacteriocin activity of L. acidophilus GK20 and L. paracasei GK74 were significantly (p<0.05) increased in MRS with FOS than without prebiotic. In conclusion, L. acidophilus GK20 and L. paracasei GK74 could be potentially used as novel probiotic strains, moreover, the combination between L. acidophilus GK20 or L. paracasei GK74 and FOS has great potential as a synbiotic.     

Probiotic strains: survival under simulated gastrointestinal conditions,in vitro adhesion to Caco-2 cells and effect on cytokine secretion

This study evaluated three probiotic strains (Lactobacillus paracasei subsp. paracasei LC-01, L. acidophilus LA-5, Bifidobacterium lactis Bb-12) and two yoghurt strains (L. delbrueckii subsp. bulgaricus LBY-27 and Streptococcus thermophilus STY-31) with regard to their resistance to simulated gastrointestinal stress, and their ability to interact with human intestinal epithelial cells. The viability of strains was analyzed by measurements of fluorescence-stained cells and their growth by plate colony-counts. The results reveal that for all tested strains, gastric emptying (above pH 3.0) would release a large number of viable cells ranging from 91% for L. paracasei to 53% for S. thermophilus into the intestinal tract, and that between 12 and 23% of them subsequently survive intestinal stress. Among them L. paracasei showed the highest resistance to gastric stress. All the bacteria adhered to the Caco-2 cell line, with the highest adhesions being observed for L. delbrueckii subsp. bulgaricus (9%) and L. acidophilus (7%). Binding of all strains to Caco-2 cells did not result in a significant increase in the production of IL-6 and IL-8 cytokines, suggesting that these bacteria do not trigger an overt inflammatory response in human intestine epithelial cells. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Utilization of <Emphasis Type="Italic">Echium amoenum</Emphasis> Extract as a Growth Medium for the Production of Organic Acids by Selected Lactic Acid Bacteria

Gol-gavzaban (Echium amoenum Fisch. & Mey.) is an indigenous herbal plant, related to the Boraginaceae family, cultivated historically in Iran. In this study, the suitability of Echium extract as a raw material for production of fermented juice by four strains of lactic acid bacteria (Lactobacillus paracasei, Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus delbrueckii) was examined. Echium extract was inoculated with these bacteria and incubated at 30 °C for 24 h. Changes in microbial population, pH, acidity, sugars, and organic acids metabolism were measured during the fermentation process. Results showed that all of the selected bacteria were capable to grow well in Echium extract without any supplementation. They all metabolized sugars including glucose, fructose and sucrose simultaneously. L. paracasei showed more affinity to sugar consumption at almost 45.2%, 38%, and 21.6% of initial glucose, fructose, and sucrose concentration, respectively. Lactic acid was produced immediately after the fermentation started. L. plantarum, L. delbrueckii, and L. acidophilus produced 6.8, 6.6, and 6.4 g/l lactic acid, respectively, which were significantly higher than that produced by L. paracasei (5 g/l). On the other hand in the case of acetic acid, L. paracasei produced significantly greater quantities in comparison with other strains (4.48 g/l). It was proved that E. amoenum was a desirable media for the production of some organic acids by all these bacterial strains.     

Effect of inulin and Lactobacillus paracasei on sensory and instrumental texture properties of functional chocolate mousse

BACKGROUND: This study evaluated the effect of a potentially probiotic bacteria (Lactobacillus paracasei subsp. paracasei LBC 82), added solely or together with the prebiotic ingredient inulin on instrumental texture attributes and sensory properties of a functional chocolate mousse during storage at 4 ± 1 °C for up to 28 days. RESULTS: The addition of Lactobacillus paracasei resulted in a firmer and more adhesive chocolate mousse. This effect was intensified with the presence of inulin in the synbiotic formulation (5.24 N and ? 0.956 N, respectively, for firmness and adhesiveness after 28 days of storage) (P < 0.05). L. paracasei population did not vary (P > 0.05) during storage (always between 7.27 and 7.35 log cfu g^?1), both for the probiotic and the synbiotic mousses. Synbiotic mousse differed from control and probiotic mousses during storage with respect to the color attribute. Moreover, both probiotic and synbiotic mousses presented taste, aroma and texture perceptions which were different from one another and from the control mousse after 14 and 21 days of storage. CONCLUSION: The use of inulin, together with the potentially probiotic strain of Lactobacillus paracasei subsp. paracasei, is advantageous, conferring potentially symbiotic potential to the chocolate mousse, as well as favorable texture and sensory properties. Copyright © 2008 Society of Chemical Industry     

Effect of long‐chain inulin on the texture profile and survival of Lactobacillus paracasei ssp. paracasei in set yoghurts during refrigerated storage

The effects of adding inulin at 20 g/L as a fat replacer and probiotic bacteria on the physicochemical and textural characteristics of yoghurt were studied. The ability of long‐chain inulin to improve the probiotic (Lactobacillus paracasei ssp. paracasei) bacteria viability in yoghurt was investigated. The addition of inulin made the texture (firmness, cohesiveness, adhesiveness and gumminess) of skimmed yoghurt similar to that of whole yoghurt, demonstrating the role of inulin as a fat replacer. However inulin increased syneresis and did not influence the viability of probiotic bacteria in the yoghurts. The addition of probiotic bacteria in yoghurts improved syneresis and increased firmness and gumminess.     

Characterization of bacteriocin-like inhibitory substances (BLIS) from lactic acid bacteria isolated from traditional Azerbaijani cheeses

The lactic acid bacteria (LAB) of southern Caucasus region present a special interest due to the diversity of lactic flora used for fermentations by various local populations during thousands of years. Four LAB strains, not identified previously, isolated from Motal and Brunza typical Azerbaijani cheeses were subjected to phenotypic identification and three of them could be identified as Lactobacillus paracasei subsp. paracasei and one as Lactobacillus rhamnosus. Test strains such as Lactobacillus bulgaricus 340 and Saccharomyces cerevisiae were inhibited by the four isolated strains. Antibacterial activity against Escherichia coli HB 101 was detected in Lactobacillus paracasei BN ATS 8w and L. rhamnosus FAZ 16m. L. paracasei BN ATS 5w and 8w, and L. rhamnosus FAZ 16m showed inhibitory effect on Staphylococcus aureus Cip 9973. The inhibition of Candida pseudotropicalis was detected only when using L. paracasei species BN ATS 5w and 7w. Culture of Listeria innocua was insensitive to the antimicrobial substances of all the studied strains. Complete inactivation or significant reduction in antibacterial activity was observed after treatment of cell-free supernatants with pronase E and proteinase K, but not with trypsin (except for L. rhamnosus FAZ 16m), indicating the protein nature of the active agents. Amylase treatment totally inactivated the substances of L. paracasei, what implies the importance of glycosylation for the activity. The activities of all the bacteriocin-like substances from studied LABs were stable over a wide pH range from 3 to 11.     

Development of novel species‐specific primers for species identification of the Lactobacillus casei group based on RAPD fingerprints

BACKGROUND: It is difficult to clearly distinguish and identify specific species of the Lactobacillus casei group using phenotypic and genotypic (16S ribosomal DNA sequence analysis) techniques alone. Some species of this group are probiotic and are widely used in the food and feed industries. The objective of this study was to develop species‐specific primers based on randomly amplified polymorphic DNA (RAPD) fingerprinting for species identification within the closely related L. casei group of bacteria. RESULTS: Three random primers termed OPT‐14, OPA‐11 and OPT‐16 were developed for analysis. The primer pairs each produced a species‐specific band found only in the tested Lactobacillus rhamnosus, Lactobacillus paracasei subsp. tolerans and Lactobacillus zeae isolates respectively. These specific fragments were then sequenced for further analysis. The species‐specific primers were designed according to cloned sequencing, which was employed for polymerase chain reaction (PCR) with the template DNA of Lactobacillus strains. Single 102, 179 and 451 bp species‐specific bands were found only in L. rhamnosus, L. paracasei subsp. tolerans and L. zeae respectively. CONCLUSION: Using PCR, the novel species‐specific primers have been shown to rapidly, accurately and effectively identify species of L. rhamnosus, L. paracasei subsp. tolerans and L. zeae from within the L. casei group of probiotic bacteria. Copyright © 2009 Society of Chemical Industry     

Direct starch conversion into L‐(+)‐lactic acid by a novel amylolytic strain of Lactobacillus paracasei B41

A new amylolytic strain of Lactobacillus paracasei able to convert starch directly into L ‐(+)‐lactic acid (LA) was isolated. The identification of the by 16S rDNA sequencing proved that this strain, B41, is the first amylolytic representative of Lactobacillus casei group. The amylase activity assay revealed that L. paracasei B41 produced extracellular amylolytic enzyme, reaching 62 U/mL in the cell‐free supernatants. The optimal conditions for its action were pH 5.0 and temperature 45°C. The gene amy1 (1779 bp) encoding the putative B41 amylopullulanase was cloned, sequenced, and analyzed. The deduced protein contained a leader peptide of 28 amino acids and a mature peptide of 564 amino acids. Compared to the amylases of closely related species, B41 enzyme had several amino acid substitutions. An inducible control at amy1 expression was demonstrated. The starch fermentation abilities of L. paracasei B41 were studied in batch processes performed with and without pH control. The highest amount of LA from starch was obtained during 48 h fermentation from 40 g/L substrate at pH maintained at 5.0–37.3 g/L. In addition, 93.3% starch conversion into LA and the highest reported productivity for 24 h were achieved – 1.30 g/L/h.     

Proteolysis in dry‐aged loins manufactured with sonicated pork and inoculated with Lactobacillus casei ŁOCK 0900 probiotic strain

Selected parameters related to proteolysis were evaluated in dry‐aged loins manufactured with sonicated pork and inoculated with Lactobacillus casei ?OCK 0900 probiotic strain. Dehydration, pH, water activity and total nitrogen content were not affected by ultrasound treatment. Neither sonication nor inoculation has an influence on L* and a* colour parameters. Sonication significantly influenced the pattern of proteolysis providing higher nonprotein nitrogen content (NPN) and proteolysis index (PI). The highest intensity of proteolysis, as assessed by NPN and PI, occurred in an inoculated sample. Neither sonication nor inoculation with L. casei had a significant effect on total viable counts. Loins inoculated with L. casei had the highest lactic acid bacteria count, followed by the sonicated and nonsonicated control. This research shows that sonication followed by inoculation with L. casei ?OCK 0900 could be used as an effective measure to speed up the proteolytic changes in dry‐aged meat cuts.     

Tuna Burgers Preserved by the Selected <Emphasis Type="Italic">Lactobacillus paracasei</Emphasis> IMPC 4.1 Strain

The use of protective microbial strains in combination with modified atmosphere packaging (MAP) and refrigerated storage on the shelf life of tuna burgers was investigated. Preliminary, the protective ability of three lactic acid bacteria (LAB) cultures (Lactobacillus casei, Lactobacillus paracasei, and Lactobacillus plantarum) have been assessed on ready-to-cook tuna burgers. Among them, L. paracasei showed the best preserving performance and significantly controlled both aerobic mesophilic bacteria and Pseudomonas spp. growth. Subsequently, the efficacy of the selected LAB culture under MAP conditions (5% O₂ and 95% CO₂) was assessed evaluating microbial and sensory quality, as well as volatile aldehyde content. Results indicated that the shelf life of burgers containing L. paracasei and packaged under MAP was 4 days longer than the control (shelf life about 6 days) and that the applied procedure represents an effective approach for the mild preservation of fish products.     

Hardaliye: fermented grape juice as a traditional Turkish beverage

Twenty-six aged hardaliye samples, collected from different spots of the Kirklareli province of Turkey and hardaliye produced in laboratory conditions using the traditional method were investigated in this study. The pH ranged from 3·21 to 3·97. Red colour (Hunter Lab a_Lvalue) of samples ranged from 1·33 to 9·66. The total bacterial count ranged from 3·5×10²to 8×10⁵cfu ml⁻¹. The lactic acid bacteria counts of the samples were found to be between 1·0×10²and 4·0×10⁴cfu ml⁻¹. Yeasts and moulds, which were found in 21 samples out of 26, ranged from 1·0×10²to 8·1×10⁴cfu ml⁻¹. Coliforms and Escherichia coli were found in none of the samples. The changes of some microbiological and chemical properties of hardaliye during fermentation were investigated. The pH of hardaliye dropped from 3·86 to 3·39. The ethanol content of the end product was determined as 595·50 mg dl⁻¹. During the fermentation process, the total bacteria count, lactic acid bacteria count and yeast count changed from 2·1×10⁵, 6·0×10⁴and 1·2×10⁵cfu ml⁻¹to 1·3×10², 1·2×10³and 1·1×10³cfu ml⁻¹, respectively.Lactobacilli isolated from hardaliye samples were characterized by API 50 CH and other phenotypic criteria. A succession of Lactobacillus species, dominated by L. paracasei subsp. paracasei and L. casei subsp. pseudoplantarum were found during the fermentation process.     

Some characteristics of Lactobacillus isolates from infant faeces

In this research, 21 strains of lactobacilli were isolated from newborn infant faeces. Lactobacillus rhamnosus (seven strains), L. paracasei ssp. paracasei (four strains), L. fermentum (four strains), L. buchneri (two strains), L. brevis (one strain), L. curvatus (one strain) and Lactobacillus sp. (two strains) isolated from infant faeces were analysed for acid production, antibiotics resistances, H₂S productions and antimicrobial activities.Inhibition activity of bacteriocins and/or bacteriocin-like substances of the lactobacilli against some food contaminants and pathogenic bacteria (Escherichia coli, Staphylococcus aureus ATCC 28213, S. aureus ATCC 2392, Yersinia enterocolitica and Bacillus cereus) were determined by the agar diffusion method.     

Kefir yeasts enhance probiotic potentials of Lactobacillus paracasei H9: The positive effects of coaggregation between the two strains

This study investigated pure Lactobacillus paracasei H9 tolerance to simulated gastrointestinal juices and adhesion to intestinal mucosa cells without yeasts, with viable yeasts (VY) and with different pretreated yeasts. Three models including gastric secretion tolerance (GST), intestinal juice tolerance (IJT) and sequential gastrointestinal tolerance (SGT) were respectively employed to assay the tolerance of L. paracasei H9, whilst Caco-2 cell line was used to investigate the bacterial adhesion. Particularly, the co-aggregation ability of the two strains at pH values of 2.0, 8.0 and 7.2 was originally carried out to study relations to the bacterial probiotic potentials. Results showed that yeast counts in the range from 3.0 to 5.0 log CFU mL^? 1 could gradually increase the viability of L. paracasei H9 in SGT. The bacterial viability in the three tolerance models and the adherent number to Caco-2 cells were significantly improved with addition of VY (P < 0.05). The L. paracasei H9 with VY in gastric juice at pH 2.0 and intestinal juice at pH 8.0, respectively, exhibited higher aggregation percentage compared with that of single L. paracasei H9 at 37 °C (P < 0.05). The aggregation ability of L. paracasei H9 with VY at pH 7.2, which might contribute to increase the adhesion of the bacteria, also excelled that of L. paracasei H9 (P < 0.05). It is deduced that proteins of the bacterial cell surface and polysaccharides in yeast cell walls play important roles in co-aggregation of the two strains and the microbial adhesion specificity to Caco-2 cells. The co-aggregation of the two strains also contributes to enhancing probiotic potentials of L. paracasei H9.