De Man Rogosa Sharpe Broth Research Articles

Impact of Novel Functional Ingredients on Lactobacillus casei Viability

Nipple fruit (Solanum mammosum), teosinte (Dioon mejiae), Caesar mushroom (Amanita caesarea), and weevil (Rhynchophorus palmarum) powders have shown great nutritional content with meaningful dietary applications. This study aspired to investigate the impact of nipple fruit, teosinte, Caesar mushroom, and weevil powders on the bile tolerance, acid tolerance, lysozyme tolerance, gastric juice resistance, and protease activity of Lactobacillus casei. Nipple fruit, teosinte, Caesar mushroom, and weevil powders were combined at 2% (wt/vol), whereas the control samples did not include the ingredients. The bile and acid tolerances were analyzed in Difco De Man–Rogosa–Sharpe broth incubated under aerobic conditions at 37 °C. The bile tolerance was investigated by adding 0.3% oxgall, whereas the acid tolerance was studied by modifying the pH to 2.0. The lysozyme tolerance was studied in electrolyte solution containing lysozyme (100 mg/L), while the gastric juice tolerance was analyzed at pH levels of 2, 3, 4, 5, and 7. The protease activity was studied spectrophotometrically at 340 nm in skim milk incubated under aerobic conditions at 37 °C. The results show that nipple fruit increased the counts, whereas Caesar mushroom and weevil powders resulted in lower counts for bile tolerance, acid tolerance, lysozyme resistance, and simulated gastric juice tolerance characteristics. Furthermore, the protease activity increased by adding nipple fruit to skim milk. According to the results, nipple fruit may improve the characteristics of L. casei in cultured dairy by-products.

Selection of a Potential Synbiotic against Cronobacter sakazakii

Cronobacter sakazakii is an opportunistic foodborne pathogen that can be fatal to infants; it is commonly associated with powdered infant formula due to contamination during manufacturing processes or during preparation in hospitals or homes. This project aimed to select a potential synbiotic, a combination of probiotic strains with a prebiotic product, to inhibit the growth of C. sakazakii in an in vitro dynamic infant gut model (Simulator of the Human Intestinal Microbial Ecosystem). A total of 16 lactic acid bacteria (LAB) were tested for their inhibitory properties against four different C. sakazakii strains by a zone of inhibition test. Lactobacillus and Pediococcus species were able to inhibit the growth (>15-mm inhibition zones) of all C. sakazakii strains tested, and only one strain from the two genera exhibited atypical resistance to tetracycline. All C. sakazakii strains and the selected LAB strains, which inhibited C. sakazakii and did not exhibit atypical antibiotic resistance, were grown in Luria-Bertani or de Man Rogosa Sharpe broth, respectively, containing 1% dextrose or 1% commercial prebiotic (w/v) to compare their ability to metabolize the prebiotic product. Overall, based on the growth inhibition of C. sakazakii, antibiotic susceptibility, and prebiotic metabolism, 6 of the 16 LAB were chosen to be part of a potential synbiotic. This study has provided valuable information that will help with the development of a synbiotic that can be used in powdered infant formula to reduce the potential for C. sakazakii-related illnesses in infants.

Polysaccharides of Weissella cibaria Act as a Prebiotic to Enhance the Probiotic Potential of Lactobacillus rhamnosus.

This work aimed to investigate the effect of EPS (extracellular polysaccharide) of Weissella cibaria as a prebiotic to promote the growth and antibacterial properties of Lactobacillus rhamnosus. The morphological, growth behavior, and antibacterial properties of L. rhamnosus were determined in MRSB(de Man Rogosa Sharpe broth) supplemented with different concentrations of EPS (0.1-2%). The results revealed that the incorporation of the EPS (2%) in MRSA improved the bacterial growth in terms of colony-forming unit (CFU, 0.7 × 105CFU/mL) compared to L. rhamnosusgrown inbare MRSA. The SEM observation revealed that EPS incorporation in the MRSBculture media does not affect the morphological properties of L. rhamnosus. Moreover, it was confirmed that the extract of probiotics cultured in MRSA supplementedwith EPS (2%) wasexhibited strong antibacterial and antibiofilm activity against targeted pathogens. ThisL. rhamnosus extract was found to bebiocompatible evidanced by erythrocyte hemolysis assay. These results confirmed that EPS regulates the growth of probiotics, resists pathogen infection, and biocompatibility.

Laktobasillerden elde edilen hücresiz süzüntülerin metisiline dirençli Staphylococcus aureus, vankomisine dirençli Enterococcus ve karbapeneme dirençli Klebsiella suşlarını inhibisyonu

Aim: Antibiotic resistance is a major health problem. Recently, probiotics are used in the field of alternative/supportive medicine. Thus, in this study, we aimed to evaluate the in vitro inhibitory effects of four different cell-free supernatants (CFSs) of lactobacilli species (L. fermentum, L. plantarum, L. acidophilus and L. rhamnosus) on clinically isolated Methicilin-resistant Staphylococcus aureus (MRSA) strains, Vancomycin-resistant Enterococcus (VRE) strains, and Carbapenem-resistant Klebsiella (CRK) strains. Materials and Methods: Lactobacillus strains were grown in de Man Rogosa Sharpe broth; after filtration, CFSs were diluted to obtain 25, 50, and 100% concentrations. Pathogen bacteria were grown in tryptic soy broth with and without CFSs in a micro-plate. The bacterial growths were measured using spectrophotometric method after four hours of incubation at 37°C. One-way ANOVA followed by Dunnett’s multiple comparisons and Kruskal-Wallis test were used for statistical analyses. Results: All tested CFSs at all concentrations were found to inhibit growth of MRSA, VRE, CRK strains; the results were found statistically significant (p<0.0001). At 50% concentrations, all CFSs were found to be most effective on MRSA growth. The CFSs of L.fermentum, L.acidophilus and L.plantarum were found to be most inhibitory at 50% concentration on VRE growth. 50% diluted CFSs of L.fermentum and L.plantarum were found to be effective on growth of CRK. All results were found statistically significant (p<0.0001). Conclusion: In our study, our results support that CFSs of lactobacilli strains inhibit growth of multi-drug resistant bacteria. Their inhibitory effects were dependent on microorganisms and CFS concentrations.

The effect of red passion fruit (Passiflora edulis Sims.) fermentation time on its activity against Extended Strain Methicillin-Resistant (ESBL) Escherichia coli and Methicillin-Resistant Staphylococcus aureus (MRSA).

The purpose of this study is to determine the effect of fermentation techniques on the inhibitory activity of red passion fruit (Passiflora edulis Sims.) fermentation filtrate in De Man Rogosa Sharpe-broth (MRS-B) media against Extended Strain Methicillin-Resistant (ESBL) Escherichia coli and Methicillin-Resistant Staphylococcus aureus (MRSA). The fruit pulp was wrapped in banana leaves before compared to direct fermentation processes. This study was divided into three treatment groups. Group 1 was the fruit pulp (5g) fermented in 45mL of MRS-B medium for 24h. Group 2 was the fruit pulp wrapped in banana leaves for 3days before fermented in MRS-B for 24h. Group 3 was the fruit pulp wrapped in banana leaves for 3days before fermentation in MRS-B for 48h. Fermentation broth of each condition was taken and then filtered using millipore (0.2µm). As many as 50µL of filtrates was tested for its inhibitory activity against E.coli ESBL and MRSA using the Kirby Bauer method. Group 2 showed the best antibacterial activity against E.coli ESBL and MRSA with the average zone of inhibition of 38.3and 37.6mm respectively. These values were higher than the first and group 3s activities. The inhibitory activity of group 1s against ESBL and MRSA is categorized as a moderate potency with a diameter of growth inhibition zone of 16-20mm, whereas the other groups are categorized as strong potency with a diameter higher than 20mm.

Inhibitory activity of fermentation filtrate of red passion fruit pulp (Passiflora edulis sims.) against Escherichia coli extended-spectrum beta-lactamase (ESBL) and methicillin resistant Staphylococcus aureus (MRSA)

This study aims to determine the minimum inhibitory concentration (MIC) and bactericidal concentration (MBC) of the fermentation filtrate (FF) on red passion fruit pulp (Passiflora edulis Sims.) against Escherichia coli Extended Spectrum Beta Lactamase (ESBL) and Methicillin Resistant Staphylococcus aureus (MRSA). The method used was the fermentation of red passion fruit pulp for 24 h using De Man Rogosa Sharpe Broth (MRS-broth) media, and the result showed that the FF of red passion fruit pulp made a dilution series concentration of 50 percent, 25 percent, 12.5 percent, 6.25 percent. Considering this result, the MIC FF of red passion fruit cells against ESBL and MRSA has a 25 percent dilution concentration, while MBC has a 50 percent dilution concentration. This shows that red passion fruit has the potential to be developed as antibacterial material, especially to fight bacteria that are already resistant.

Characterization and Growth under Different Storage Temperatures of Ropy Slime–Producing Leuconostoc mesenteroides Isolated from Cooked Meat Products

The presence of lactic acid bacteria can be detrimental when the abundant growth of slime-producing strains (Lactobacillus spp. and Leuconostoc spp.) causes spoilage of meat products. Two strains of lactic acid bacteria were isolated from vacuum-packed cooked hams that had been withdrawn from the market for the so-called ropy slime defect and identified as Leuconostoc mesenteroides. In an attempt to define the behavior of ropy slime-producing bacteria, two strains of L. mesenteroides were incubated in de Man Rogosa Sharpe broth at different storage temperatures and conditions of thermal abuse (4, 12, 20, 30, 37, and 44°C). Both strains showed a lack of growth at 44°C, a good level of development at 30 and 37°C, and evident growth ability at low temperatures, with a long stationary phase. In particular, the bacterial concentration at 4°C was >105 CFU mL-1 after more than 120 days of incubation. This study demonstrates that the refrigeration temperature for cooked meat products does not constitute a hurdle for ropy slime producers and their subsequent ability to spoil.

Development and viability of probiotic orange juice supplemented by Pediococcus acidilactici CE51

Several studies demonstrate that dairy products are the main foodstuffs that employ probiotic bacteria in their composition. The main objective of this study was to characterize the CE51 isolate as a potential probiotic strain and also develop and evaluate the viability of probiotic orange juice drink. In total, 152 lactic acid bacteria were isolated from food samples. The bacteriocin-like substance producing isolate was sequenced by 16S rDNA. Probiotic potential was evaluated by survival in de Man Rogosa Sharpe broth in pH 2.0, 2.5, and 3.5 and in the presence of bile salts (0.3, 0.6, and 0.9%) for up to 180 min. Probiotic orange juice was developed at pH4.5 and pH6.5 with an initial inoculum of 106 CFU/ml. The juices were stored at 4 °C and 30 °C for up to 35 days. Only one isolate presented antimicrobial activity against Listeria monocytogenes which was genetically identified as Pediococcus acidilactici CE51. The probiotic potential was confirmed by its resistance to acid pH and bile salts presence. The two probiotic juice formulations presented counts between 7.2 and 8.5 log CFU/ml after 35 days at 4 °C and 30 °C. Therefore, orange juice could act as an ideal food matrix for probiotic beverage of Pediococcus acidilactici CE51.

The efficacy of cell-free supernatants from Lactobacillus plantarum Cs and Lactobacillus acidophilus ATCC 314 for the preservation of home-processed tomato-paste

The unsafety concern associated with the chemical preservatives and the understanding of the preservative potential of lactic acid bacteria on varied food substances led to the present study which was aimed at the evaluation of the bio-preservative potential of L. plantarum Cs and L. acidophilus ATCC 314 on home-processed tomato paste. The test organisms were activated in glucose supplemented deMan Rogosa Sharpe broth under stationary condition at 37 °C for 36 h to produce cell-free supernatants (CFSs) which were concentrated to 50% with 5 M sucrose solution and precipitated with 4 °C acetone respectively. The treated CFSs were first exposed to chemical analysis prior to their antimicrobial sensitivity to the indicator organisms (Staphylococcus aureus, Escherichia coli, Aspergillus niger and Aspergillus flavus). The minimum inhibitory concentration (MIC) of the most active CFS was selected for shelf-life study on home-processed tomato paste at room temperature for 45days. Among the detectable amount of CFS biomolecules, a significant (P>0.05) high amount of lactic acid (6.491±0.017 mg/ml) was recovered from concentrated CFS from L. acidophilus ATCC 314 while precipitated CFS from L. plantarum Cs had the highest significant protein molecules (0.863±0.013 mg/ml). However, the concentrated CFS (cCFS) from both test organisms at 100% demonstrated the strongest antimicrobial activity to all the indicator organisms among the other two CFSs. Their inhibitory effect was greater on Staphylococcus aureus (11.9±0.10–12.85 ± 0.08 mm) than E. coli (7.57 ± 0.06–8.15±0.05 mm) and Aspergillus niger (5.94 ± 0.08–6.98 ± 0.06) than Aspergillus flavus (5.05± 0.04–5.60 ± 0.05). The L. plantarum Cs and L. acidophilus ATCC 314 cCFSs- treated tomato pastes significantly (P>0.05) extended the pastes shelf-life to 25 and 30 days respectively. However, the 5 days’ shelf-life extension of the tomato paste by L. acidophilus ATCC 314 cCFS as compared to that from L. plantarum Cs was insignificant (P>0.05). The increase in shelf-life of the home-processed tomato paste suggests the possible use of L. plantarum Cs and L. acidophilus ATCC 314 CFS as bio-preservatives in tomato processing.

Inactivation of Lactobacillus Virulent Bacteriophage by Thermal and Chemical Treatments

The uses of thermal and chemical treatments were evaluated with respect to the inactivation of the Lactobacillus virulent bacteriophage P2. Thermal treatments consisted of heating the phage at 63, 72, and 90°C in three broth media: de Man Rogosa Sharpe broth, reconstituted skim milk, and Tris magnesium gelatin buffer. Chemical treatments evaluated were ethanol, isopropanol, sodium hypochlorite, and peracetic acid at various concentrations. Phage P2 was completely inactivated in 20 and 5 min at 72 and 90°C, respectively. Reconstituted skim milk and de Man Rogosa Sharpe broth provided optimum and minimum heat protection, respectively. Only sodium hypochlorite at 400 and 800 ppm completely inactivated the phage in 50 and 30 min, respectively. Treatment with 100% ethanol and isopropanol resulted in only a ca. 5.1-log reduction. Peracetic acid at the highest concentration used (0.45%) resulted in only a 1.40-log reduction of the phage within 60 min. These results provide additional data for establishing effective methods of controlling phage contamination in dairy and laboratory environments.

Analysis of T-2 Toxin Removal Factors in a Lactococcus Fermentation System

The objective of this work was to determine the bacterial strains and factors that most efficiently degrade T-2 toxin in foods or animal feed. To determine the most efficient strain and optimal incubation times for degradation of T-2, the rate of T-2 removal by three lactic acid bacteria strains was quantified by liquid chromatography plus tandem mass spectrometry after incubation in de Man Rogosa Sharpe broth with 50 ng mL-1 T-2 at 37°C for 96 h. Various components of the most efficient degradation strain fermentation systems were extracted, and the ability to remove T-2 was assayed. Lactococcus lactis CAMT22361 was the most efficient degradation strain for removing T-2. Yeast extract powder interfered with L. lactis CAMT22361 in the degradation process. T-2 toxin was removed by various components of the L. lactis CAMT22361 cells in the following order: nonprotein material of the extracellular fraction > protein in the extracellular fraction > whole cell ≈ cell wall > cell intracellular matrix fluid. T-2 removal rates were 54.08% ± 0.79%, 43.65% ± 0.84%, 43.09% ± 0.87%, 41.98% ± 0.8%, and 23.45% ± 0.66%, respectively. The nonprotein fraction in the extracellular fluid was most likely the key component in L. lactis CAMT22361 and hence would be the most desirable cellular component to be used to remove T-2 from food or feed.

Probiotic characterization of lactic acid bacteria isolated from swine intestine.

Aim:A study was conducted with the objective to isolate probiotic microorganisms from swine intestine.Materials and Methods:In this study 63 isolates (24 caeca, 24 colon mucosal scrapings, and 15 rectal swab samples) were collected from Large White Yorkshire pigs. The isolates were inoculated and grown in de Man Rogosa Sharpe broth at 37°C with 5% CO2 for 48 h and subjected to morphological identification. Colonies having Gram-positive rods were selected for further physiological and biochemical identification tests, which were conducted in triplicate in two runs for each of the selected isolates using a standard protocol. Probiotic properties among the identified species were determined through the implementation of several tests related with pH tolerance, bile tolerance, and antimicrobial activity.Results:Morphological identification revealed that only 23 isolates were Gram-positive rods. Physiological tests performed on these 23 isolates further revealed that four of them did not exhibit any growth, at all conditions studied. The rest 19 isolates were, therefore, selected and subjected to biochemical tests. Six isolates were rejected because they were oxidase and nitrate reduction positive. From the 13 isolates subjected to sugar fermentation tests, speciation of only two isolates could be ascertained, one of the isolates showed characteristics for Lactobacillus acidophilus and the other for Lactobacillus plantarum. These two isolates were assessed for the strain possessing maximum probiotic property, and it was inferred that both – L. plantarum and L. acidophilus could tolerate a wide pH range (2-9), a wide bile concentration (0.05-0.3%) and revealed antimicrobial activity toward Escherichia coli, and Enterobacter spp.Conclusion:L. plantarum and L. acidophilus were isolated from swine intestine and were found to have good probiotic properties.

The γ-aminobutyric acid-producing ability under low pH conditions of lactic acid bacteria isolated from traditional fermented foods of Ishikawa Prefecture, Japan, with a strong ability to produce ACE-inhibitory peptides

Many traditional fermented products are onsumed in Ishikawa Prefecture, Japan, such as kaburazushi, narezushi, konkazuke, and ishiru. Various kinds of lactic acid bacteria (LAB) are associated with their fermentation, however, characterization of LAB has not yet been elucidated in detail. In this study, we evaluated 53 isolates of LAB from various traditional fermented foods by taxonomic classification at the species level by analyzing the 16S ribosomal RNA gene (rDNA) sequences and carbohydrate assimilation abilities. We screened isolates that exhibited high angiotensin-converting enzyme (ACE) inhibitory activities in skim milk or soy protein media and produced high γ-aminobutyric acid (GABA) concentrations in culture supernatants when grown in de Man Rogosa Sharpe broth in the presence of 1% (w/v) glutamic acid. The results revealed that 10 isolates, i.e., Lactobacillus buchneri (2 isolates), Lactobacillus brevis (6 isolates), and Weissella hellenica (2 isolates) had a high GABA-producing ability of>500mg/100ml after 72h of incubation at 35°C. The ACE inhibitory activity of the whey cultured with milk protein by using L. brevis (3 isolates), L. buchneri (2 isolates), and W. hellenica (2 isolates) was stronger than that of all whey cultured with soy protein media, and these IC50 were<1mg protein/ml. Three of 10 isolates had high GABA-producing activities at pH 3, suggesting that they could be powerful candidates for use in the fermentation of food materials having low pH.

Free radical formation by Lactobacillus acidophilus NCFM is enhanced by antioxidants and decreased by catalase

Lactobacillus acidophilus NCFM was found to increase the production of transient radicals during growth in a 1:1 mixture of brain heart infusion broth and de Man–Rogosa–Sharpe broth as detected by electron spin resonance (ESR) spectroscopy using spin trapping. During growth of L. acidophilus NCFM addition of quercetin, rutin or a whey protein hydrolysate, normally all with antioxidant activity, further increased formation of transient radicals. Such increase in the level of radicals in the growth medium did not have an adverse effect on the viability of L. acidophilus NCFM, but may be involved in inhibition of pathogenic bacteria by L. acidophilus. Catalase decreased the production of radicals without effect on the growth of the catalase-negative L. acidophilus NCFM, whereas superoxide dismutase had no effect on radical production, but hampered bacterial growth. The effect of catalase may be explained by non-radical removal of hydrogen peroxide otherwise being a precursor for hydroxyl radicals formed by transition metal catalysis. Metal ion concentrations decreased in the medium during bacterial growth, which may be the result of transport across bacterial membranes of redox active metal ions like iron and copper chelated by the antioxidant competing with reductive cleavage of hydrogen peroxide forming hydroxyl radicals. Antioxidants may accordingly promote probiotic effect of catalase-negative bacteria through increased formation of reactive oxygen species.

Utilisation of steviol glycosides from Stevia rebaudiana (Bertoni) by lactobacilli and bifidobacteria in in vitro conditions

In the current study, eight strains of bifidobacteria and seven strains of lactobacilli were tested for their ability to grow in the presence of rebaudioside A and steviol glycosides from the sweetener Natusweet M001 originating from herb Stevia rebaudiana (Bertoni). Stevia is gaining popularity as a natural, non-caloric sugar substitute, and recently, it was allowed as a food additive by European Union too. Utilisation of steviol glycosides by intestinal microbiota suggests that they might have potential prebiotic effect. Based on the evaluation of bacterial density and pH values in our in vitro study, it was found that lactobacilli and bifidobacteria tested were able to utilise steviol glycosides as a carbon source only to a very limited extent. All strains tested showed significantly lower change in the absorbance A540 (P < 0.05) and pH decrease of the growth media as compared with the positive controls (medium containing glucose as a carbon source and de Man Rogosa Sharpe broth). We concluded that a suggested prebiotic effect was not confirmed either in the case of rebaudioside A or in the case of the sweetener Natusweet M001 containing a mixture of steviol glycosides.

Production of Tyramine by Enterococcus faecalis Strains in Water-Boiled Salted Duck

AbstractThe potential to produce biogenic amines was investigated with 15 Lactococcus lactis and 15 Enterococcus faecalis strains isolated from water-boiled salted duck. The production of biogenic amines from the isolated strains grown in de Man Rogosa Sharpe broth containing precursor amino acids was determined by thin-layer chromatography and high-performance liquid chromatography. None of the L. lactis strains produced any biogenic amines, whereas 12 strains of E. faecalis produced tyramine and β-phenylethylamine. PCR assays were used to detect the presence of tyrosine decarboxylase genes in all of the isolated strains. Only the 12 biogenic amine--producing Enterococcus strains had a 924-bp fragment characteristic for the tyrosine decarboxylase gene. The comparison of the amplified partial tyrDC gene sequences of the 12 positive Enterococcus strains revealed 99% similarity within the same species. The tyramine production of the sterilized water-boiled salted duck inoculated with E. faecalis R612Z1 increased significantly during storage. This study reveals that the isolated E. faecalis strains can produce tyramine and β-phenylethylamine in the medium; however, they can only produce tyramine in water-boiled salted duck.

Influence of NaCl reduction and replacement on the growth of Lactobacillus sakei in broth, cooked ham and white sauce

The growth inhibiting effects of NaCl and selected simple salt replacers (CaCl 2, MgCl 2, KCl and MgSO 4) on the growth of Lactobacillus sakei were studied in de Man Rogosa Sharpe broth at 7 °C over a water phase concentration of 0 to 6.4%. The divalent chloride salts (CaCl 2 in particular) generally had the largest antimicrobial activities at equivalent water phase concentrations, molalities or water activity ( a w) values. MgSO 4 had not only the least antimicrobial activity but also the smallest a w depressing capacity. The results also showed that the antimicrobial effects of CaCl 2 were not fully accounted for by its a w depressing effects. Challenge tests performed on cooked ham and white sauce showed that reduction of NaCl levels by 28 and 33%, respectively, had no influence on the microbial stability of these products to L. sakei. Ultimately the study concluded that the microbiological consequences of the full or partial replacement of NaCl on the growth of L. sakei largely depend on the initial level of NaCl, the level of replacement and the nature of the salt replacer used. Altered stability to L. sakei is most likely given a high initial NaCl level, combined with a large level of partial replacement with either CaCl 2 (increased stability) or MgSO 4 (reduced stability) as the replacer.

Oral administration ofLactobacillus acidophilusinduces IL-12 production in spleen cell culture of BALB/c mice bearing transplanted breast tumour

Lactic acid bacteria can affect the maturation of immune cells and their products not only in the gut but also on the systemic immune organs such as lymph nodes and spleen. In the present work, we studied the effects of oral administration of Lactobacillus acidophilus on the immune responses of BALB/c mice bearing transplanted breast tumour. Two groups of female inbred BALB/c mice, each containing nine mice as test and control, were used. The L. acidophilus ATCC4356 strain was inoculated in DeMan-Rogosa-Sharpe broth and cultivated for 24 h at 37 degrees C. Then, it was collected by centrifugation, and was washed and suspended in PBS. Afterwards, 0.5 ml/d of this suspension, which contained 2.7 x 108 colony forming units/ml of bacteria, was orally administered to the mice by gavage, 14 d before tumour transplantation and 30 d after that with 3-d intervals. Similar to the test mice, the control mice received an equal volume of PBS. The results showed that oral administration of L. acidophilus increased the production of IL-12 (P < 0.05) and decreased the level of transforming growth factor beta (P = 0.05) in the splenocyte culture. Moreover, the growth rate of tumour in the test mice decreased (P < 0.01), and the results of delayed-type hypersensitivity assay after 48 h were risen (P < 0.05) in comparison with the controls. Results suggest that daily consumption of L. acidophilus can improve the production of immunomodulatory cytokine IL-12 in the splenocyte culture, which was stimulated by tumour antigen in BALB/c mice bearing transplanted breast tumour. But further studies are needed to find out some other possible mechanisms of this effect.

Thermal, chemical, and photocatalytic inactivation of Lactobacillus plantarum bacteriophages.

The effect of several biocides, thermal treatments, and photocatalysis on the viability of four Lactobacillus plantarum phages was investigated. Times to achieve 99% inactivation (T99) of phages at 63, 72, and 90 degrees C were evaluated in four suspension media: deMan Rogosa Sharpe broth, reconstituted skim milk, a commercial EM-glucose medium, and Tris magnesium gelatin buffer. The four phages studied were highly resistant to 63 degrees C (T99 > 45 min); however, counts < 10 PFU/ml were achieved by heating at 90 degrees C for 5 min. Higher thermal resistance at 72 degrees C was observed when reconstituted skim milk and EM-glucose medium were assayed. Peracetic acid (0.15%, vol/vol) was an effective biocide for the complete inactivation of all phages studied within 5 min of exposure. Sodium hypochlorite (800 ppm) inactivated the phages completely within 30 min. Ethanol (100%) did not destroy phage particles even after 45 min. Isopropanol did not have any effect on phage viability. Phage counts < 50 PFU/ml were obtained within 180 min of photocatalytic treatment. The results obtained in this work are important for establishing adequate methods for inactivating phages in industrial plants and laboratory environments.

Individual Effects of Sodium, Potassium, Calcium, and Magnesium Chloride Salts on Lactobacillus pentosus and Saccharomyces cerevisiae Growth

A quantitative investigation on the individual effects of sodium (NaCl), potassium (KCl), calcium (CaCl2), and magnesium (MgCl2) chloride salts against Lactobacillus pentosus and Saccharomyces cerevisiae, two representative microorganisms of table olives and other fermented vegetables, was carried out. In order to assess their potential activities, both the kinetic growth parameters and dose-response profiles in synthetic media (deMan Rogosa Sharpe broth medium and yeast-malt-peptone-glucose broth medium, respectively) were obtained and analyzed. Microbial growth was monitored via optical density measurements as a function of contact time in the presence of progressive chloride salt concentrations. Relative maximum specific growth rate and lag-phase period were modeled as a function of the chloride salt concentrations. Moreover, for each salt and micro-organism tested, the noninhibitory concentrations and the MICs were estimated and compared. All chloride salts exerted a significant antimicrobial effect on the growth cycle; particularly, CaCl2 showed a similar effect to NaCl, while KCl and MgCl2 were progressively less inhibitory. Microbial susceptibility and resistance were found to be nonlinearly dose related.