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Seventy strains of lactic acid bacteria were investigated for nitrite reductase activity. Two types of this activity were detected. Type I was found in Lactobacillus plantarum, L. pentosus and Pediococcus pentosaceus. This activity is heme-dependent with ammonia as the sole product. Type II mechanism is heme-independent and reduces nitrite to NO and N2O.
In the present study, soymilk is fermented with lactic acid bacteria (Streptococcus thermophilus BCRC 14085, Lactobacillus acidophilus BCRC 14079) and bifidobacteria (Bifidobacterium infantis BCRC 14633, B. longum B6) individually, and in combination. The change in the content of various isoflavones (aglycones, glucoside, acetyl- and malonyl-glucosides) and the beta-glucosidase activity in soymilk during fermentation is investigated. It is observed that fermented soymilk contains a lower total isoflavone content (81.94-86.61 microg/ml) than soymilk without fermentation (87.61 microg/ml). Regardless of starter organism employed, fermentation causes a major reduction in the contents of glucoside, malonylglucoside and acetylglucoside isoflavones along with a significant increase of aglycone isoflavones content. The level of change in the content of various isoflavones and beta-glucosidase activity after fermentation varies with the starter organism. Among all the fermented soymilks tested, soymilk fermented with S. thermophilus showed the highest beta-glucosidase activity and the greatest increase in the contents of aglycones. The percentage of daidzein, genistein and glycitein to total isoflavone content in S. thermophilus-fermented soymilk increases from an initial 14.24%, 6.89% and 2.45%, respectively, to 36.20%, 28.80% and 12.44% after 24h of fermentation. Finally, the increase of aglycones and decrease of glucoside isoflavones during fermentation coincides with the increase of beta-glucosidase activity observed in fermented soymilk.
The technological properties of 96 lactic acid bacteria isolated from Lebanese traditional fermented milk "laban" were characterised. They were classified by phenotypic and biochemical analyses as Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, thus indicating that laban is a fermented milk similar to yogurt. Most strains of L. bulgaricus (87.5%) exhibited a high acidification activity, whereas strains of streptococci showed low acidification ability. 33.3% of streptococci strains and 25% of lactobacilli strains displayed similar acidification performances as European strains. Results obtained for syneresis, texture and rheological parameters led us to consider that isolated strains were not low polymer-producing strains. Some of them displayed interesting characteristics such as low syneresis and high values for rheological parameters. The major flavour compounds found in pure cultures were acetaldehyde, acetone, 2-butanone, dimethyl disulfide, acetoin, 2,3-butanedione, 2,3-pentanedione, and acetic, hexanoic and butanoic acids. Acetaldehyde (7.4%) and organic acids (48.3%) were mainly produced by L. bulgaricus strains, whereas streptococci cultures contained high relative levels of 2,3-butanedione and acetoin, which represented around 82% of the total flavour compounds. Finally, strains isolated from laban samples exhibited different technological properties than those used in yogurt production, thus conferring specific characteristics to this product.
In this study, soymilk was first fermented with lactic acid bacteria (Streptococcus thermophilus, Lactobacillus acidophilus) and bifidobacteria (Bifidobacterium infantis, Bifidobacterium longum) both individually and simultaneously. Mutagenicity and the suppression of fermented soymilk against the mutagenesis induced by 4-nitroquinoline-N-oxide (4-NQO), a direct-acting mutagen, and 3,2'-dimethyl-4-amino-biphenyl (DMAB), an indirect-acting mutagen, on Salmonella typhimurium TA 100, was then investigated. It was found that the fermented soymilk shows no mutagenic activity on Sal. typhimurium TA 100. Fermentation, in general, significantly (p<0.05) enhanced the antimutagenicity of soymilk. The levels of increased antimutagenicity of fermented soymilk varied with the starter organism and the type of mutagen tested. Although unfermented soymilk exerted lower antimutagenic activity against DMAB than 4-NQO, the fermented soymilk, generally, showed a higher antimutagenic activity against DMAB than 4-NQO. Among the various fermented soymilk tested, soymilk fermented with both Str. themophilus and B. infantis simultaneously exhibited the highest antimutagenicity of 85.07% and 85.78%, respectively, against 4-NQO and DMAB Further investigation on this fermented soymilk revealed that both the antimutagenic factors formed during fermentation and the cells of the starter organisms contributed to the increased antimutagenic activity against DMAB, while the former led to the increased activity against 4-NQO.
In the present study, lactic acid bacteria (LAB) from the cecum of chickens bred either under intensive (commercial broilers) or extensive (free-range) conditions were isolated, identified and some of their probiotic characteristics determined. The LAB identified by 16S-23S rRNA PCR-ARDRA were mainly of Lactobacillus species and to a lesser extent of Enterococcus spp. for all animals. Free-range chickens showed a higher presence of Lactobacillus acidophilus while Lactobacillus reuteri and Lactobacillus johnsonii were more frequently recovered from commercial broilers. Lactobacillus crispatus was found only in commercial broilers, Lactobacillus vaginalis and Lactobacillus agilis only in free-range chickens and Lactobacillus salivarius in both types. Enterococcus isolates from ceca of commercial broilers showed a higher resistance to antimicrobial drugs. Lactobacillus isolates from free-range chickens presented a higher frequency of in vitro antagonistic activity against selected pathogens than from commercial broilers. All LAB isolates had predominantly non-hydrophobic surfaces, but with variations depending on age of the chickens and breeding conditions. Animal breeding caused variation on composition, antimicrobial susceptibility, antagonistic activity and surface hydrophobicity of LAB from chicken cecum. LAB isolates from ceca of free-range chickens have potential as probiotic agents, which may be used in the future as replacing the use of antimicrobials as growth promoters.
The physiological responses of the lactic acid bacteria Pediococcus pentosaceus and Tetragenococcus halophila (formely known as P. halophila), subjected to osmotic stress in the presence of molecules known to act as osmoprotectants for other bacteria were studied. In a defined medium, glycine betaine, dimethylsulfonioacetate, choline, proline and L-carnitine were able to relieve inhibition of growth at 0.8 M NaCl. The five compounds were shown to efficiently compete with glycine betaine transport, suggesting the existence of common transporter(s) for these molecules. T. halophila, the most tolerant strain, exhibited a larger spectrum of compatible solutes including dimethylsulfonioacetate, dimethylsulfoniopropionate and ectoine. Preliminary data suggest that restoration of growth by ectoine under osmotic constraint seems specific to the genus Tetragenococcus.
Previous studies have indicated that the lactic acid bacterium Lactobacillus rhamnosus HN001 can enhance immune function in mice, following oral delivery. However, the influence of bacterial cell viability on immunoenhancement, and the optimum dose of HN001 required for this effect, have not been determined. In the present study, both live and heat-killed preparations of L. rhamnosus HN001 were shown to enhance the phagocytic activity of blood and peritoneal leucocytes in mice, at a dose of 109 micro-organisms daily. In contrast, only live HN001 enhanced gut mucosal antibody responses to cholera toxin vaccine. Feeding mice with 107 viable HN001/d for 14 d was shown to enhance the phagocytic capacity of blood leucocytes, with incremental enhancement observed at 109 and 1011 daily doses. In contrast, a minimum dose of 109 viable HN001/d was required to enhance the phagocytic activity of peritoneal leucocytes, and no further increment was observed with 1011 daily. This study demonstrates that L. rhamnosus HN001 exhibits dose-dependent effects on the phagocytic defence system of mice, and suggests that while the innate cellular immune system is responsive to killed forms of food-borne bacteria, specific gut mucosal immunity may only be stimulated by live forms.
AIMS: Screening for lactic acid bacteria (LAB) producing bacteriocins and other antimicrobial compounds is of a great significance for the dairy industry to improve food safety. METHODS AND RESULTS: Six-hundred strains of LAB isolated from 'rigouta', a Tunisian fermented cheese, were tested for antilisterial activity. Eight bacteriocinogenic strains were selected and analysed. Seven of these strains were identified as Lactococcus lactis and produced nisin Z as demonstrated by mass spectrometry analysis of the purified antibacterial compound. Polymerase chain reaction experiments using nisin gene-specific primers confirmed the presence of nisin operon. Plasmid profiles analysis suggests the presence of, at least, three different strains in this group. MMT05, the eighth strain of this antilisterial collection was identified, at molecular level, as Enterococcus faecalis. The purified bacteriocin produced by this strain showed a molecular mass of 10 201.33 +/- 0.85 Da. This new member of class III bacteriocins was termed enterocin MMT05. CONCLUSIONS: Seven lactococcal strains producing nisin Z were selected and could be useful as bio-preservative starter cultures. Additional experiments are needed to evaluate the promising strain MMT05 as bio-preservative as Enterococci could exert detrimental or beneficial role in foods. SIGNIFICANCE AND IMPACT OF THE STUDY: Only a few antibacterial strains isolated from traditional African dairy products were described. The new eight strains described herein contribute to the knowledge of this poorly studied environment and constitute promising strains for fermented food safety.
The rate of lactic acid (LA) permeation from brain tissue to venous blood and utilization in brain tissue was investigated in 13 isolated dog brains before and after an ischemic period of 3 min. LA concentration in the brain, cerebral blood flow, as well as the arteriovenous differneces of LA, glucose, and O2 were determined. LA concentration in cerebral tissue increased from a control value of 254 +/- 42 to 1,606 +/- 177 mumol/100 g brain tissue in the 2nd min after ischemia (mean values +/- SE). Before ischemia no release of LA was found, whereas in the 2nd min after ischemia LA permeation rate had increased to 25.1 +/- 8.5 mumol/100 g brain tissue per minute (P less than 0.005). Up to the 4th min after ischemia no net LA utilization was observed. Thereafter LA utilization increased rapidly and exceeded the LA permeation rate by a ratio of maximally 10:1 between the 12th and 21st min after ischemia. The O2 equivalent of the cerebral metabolic rate for lactate maximally amounted to 2.82 +/- 0.42 mumol-min-1-g-1 or 181 +/- 28%. LA output may be limited by passage of LA across the brain cell and the blood-brain barrier.
Intracellular acidosis due mainly to lactic acid accumulation has been regarded as the most important cause of skeletal muscle fatigue. Recent studies on mammalian muscle, however, show little direct effect of acidosis on muscle function at physiological temperatures. Instead, inorganic phosphate, which increases during fatigue due to breakdown of creatine phosphate, appears to be a major cause of muscle fatigue.
Lactic acid bacteria (LAB) consist of many genera, Gram-positive, and nonspore-forming micro-organisms; some members being used as probiotics while some others have negative effects on pig health. Bacterial species in the gastrointestinal tract can produce antibacterial substances, reduce serum cholesterol in their host, or can be responsible for growth reduction, diarrhea, and intestinal epithelial damage. It is therefore important for the pig industry to evaluate the impact of food and farm management on the presence of "good" or "bad" bacteria and the risk for consumers. This articles focuses on the molecular identification of gut microflora species following different diets given to pigs in UK and correlating the data on growth, health, and welfare. First of all, pig feces were individually collected from sows before and after farrowing and also from piglets before and after weaning over several months. Bacteria colonies were grown on MRS agar plates from feces and DNA was extracted (QIAamp DNA stool kit) and amplified using 16S rDNA (27f and 519r) primers. DNA sequencing and sequence alignment allowed us to identify species-specific zones, which were used as probes in a macroarray system also known as reverse line blot hybridization. Some probes were found to be species specific for the following species: Lactobacillus acidophilus, L. animalis, L. gallinarum, L. kitasanotis, L salivarius, Streptococcus alactolyticus, S. hyointestinalis, and Sarcina ventriculi. Actual studies are now focusing on the impact of diets of the microflora in different gut parts and at different stages of the animal's life.
Twenty-six out of 46 representative lactic acid bacteria (LAB) that we isolated from 36 dogs in a previous study were agglutinated by concanavalin A (ConA) at a concentration of 0.1563 mg/ml, while isolates did not agglutinate without the addition of ConA. Amongst the isolates, L. reuteri, L. mucosae, and E. canintestini agglutinated strongly, while L. gallinarum, L. kitasatonis, L. acidophilus, L. saerimneri, B. animalis ssp. animalis, P. acidilactici, and E. hirae did not agglutinate. ConA-agglutination of LAB was specifically inhibited by D-glucose, D-galactose, and D-mannose at a concentration of 1.563 mg/ml. Among the sugars, ConA-agglutination was strongly inhibited by D-mannose, while the inhibition level by D-glucose and D-galactose were lower than that of D-mannose. ConA- agglutination of all the LAB isolates was inhibited by D-mannose, except for L. reuteri (one species) and L. mucosae (two species). ConA-agglutination of Bifidobacterium spp. was inhibited by only D-mannose. Based on our results, ConA-agglutination of LAB seems to be strain-specific, but not species-specific.
Effects of the administration of heat treated cells of intestinal lactic acid bacteria were examined in rats fed a deoxycholic acid (DCA) diet. Male Wistar rats were given a 0.25% DCA diet with or without the heat treated cells of Enterococcus faecalis AD 1001 (EFH-1) or Lactobacillus reuteri AD 0002 (LRH-2) for 4 weeks. Abnormal increases in serum GOT, GPT, UN and lipoproteins were observed in the rats fed the DCA diet. Furthermore, severe lesions in the kidney as well as in the liver were found in these rats. On the contrary, the increases in serum GOT, UN, VLDL and LDL were significantly suppressed, and markedly fewer lesions in the liver and the kidney were observed in the rats fed the DCA diet plus EFH-1 or LRH-2.
Forty-seven salt-tolerant lactic acid bacteria, which had been isolated from different places and grown in 15% NaCl, were examined to assess their taxonomic heterogeneity. Among the isolates, 42 were isolated from shoyu mash during the acid fermentation phase, 2 were from miso and 3 were from anchovy pickles. All isolates were identified as Tetragenococcus halophilus on the basis of DNA relatedness values. We further examined 102 phenotypic characteristics of them. The isolates exhibited differences in only 16, supporting the conclusion obtained from the DNA relatedness analysis.
A method has been developed to identify phage containing mesophilous lactic acid streptococci. The method is based on the chloroform treatment of young cultures. The isolated moderate phages P4St and P6St are morphologically identical and serologically related to one another and to virulent phages P1Sv, P2Sv, P3Sv, P12Sv, P13Sv that can be isolated in industrial phagolysis.
We sought to determine the longitudinal distribution of pulmonary vascular resistance (PVR) in acute lactic acidosis utilizing pulmonary artery and vein balloon occlusion techniques (Holloway et al. J. Appl. Physiol. 54: 840-851, 1983). In anesthetized dogs, both a systemic vein (I-V) infusion and systemic artery (I-A) infusion of L-lactic acid were studied to control for potential effects of factors other than pH on PVR. During progressive I-A infusion (n = 9) to a pH of 6.94 +/- 0.06 there was no significant change in PVR or its distribution. In contrast, I-V infusion (n = 9) to a pH of 7.08 +/- 0.09 increased median PVR from 3.6 to 21.7 mmHg.1(-1).min (P less than 0.001), due to an increase in middle segment resistance (0.0-15.4 mmHg.1(-1).min, P less than 0.02). Examination by light and electron microscopy demonstrated pulmonary capillary obstruction with hemolyzed erythrocyte (RBC) membranes with I-V infusion, but representative I-A animals did not demonstrate these findings. Conceivably, the systemic vascular bed filtered the fragmented RBC membranes in the I-A model, but this microvascular obstruction with altered RBCs and RBC fragments caused the pulmonary hypertension observed in the I-V infusion. We conclude that lactic acidosis does not increase pulmonary vascular tone in dogs, a finding compatible with most previous studies in which observed increases in PVR may be attributed to other effects from I-V acid infusion on circulating blood elements.
Molecular orientation distributions in the crystalline and amorphous regions of a biaxially oriented poly(L-lactic acid) film were analyzed fully by polarized Raman spectroscopy. Raman bands at 926 and 875 cm(-1) were chosen for the determination of the most probable molecular orientation distribution functions for the crystalline and amorphous regions in the film. It was revealed that the PLLA molecules were oriented biaxially in both the crystalline and amorphous regions. The orientation distribution normal to the film surface was found to be broader in the amorphous regions than in the crystalline regions. Furthermore, a predominant unidirectional molecular orientation was observed in the crystalline regions, whereas the molecular orientation distribution in the amorphous regions was isotropic in the plane parallel to the film surface. The different behavior of the crystalline and amorphous regions suggests that each region underwent different deformation mechanisms during the film formation.
Biodegradable intravitreal rod-shaped implants containing dexamethasone sodium m-sulfobenzoate (DMSB) were prepared from blends of poly(DL-lactic acid) (PLA) with number-average molecular weight 2000 (PLA2000) and 4000 (PLA4000). The effect of the fraction of PLA2000 on the release of DMSB from the implant was investigated after implantation in the vitreous body of rabbit eyes. After the initial burst, the drug was released slowly from the blended PLA implants with a PLA2000 fraction of below 30 wt% in normal eyes within a period of 28 d. For the implants with a higher PLA2000 fraction of over 50 wt%, the drug was released following approximately first order kinetics. In the vitrectomized eyes, the release of DMSB from the PLA2000/PLA4000 (5/5) implant was 2.5 times more rapid than in normal eyes, and the clearance of drug was also appreciably accelerated as compared with that in normal eyes.