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PubMed2003

Identification of lactic acid bacteria from spoilage associations of cooked and brined shrimps stored under modified atmosphere between 0 degrees C and 25 degrees C.

AIMS: To evaluate spoilage and identify lactic acid bacteria (LAB) from spoilage associations of cooked and brined shrimps stored under modified atmosphere packaging (MAP) at 0, 5, 8, 15 and 25 degrees C. METHODS AND RESULTS: Bacterial isolates (102) from spoilage associations of cooked and brined MAP shrimps were characterized by phenotypic tests and identified as lactic acid bacteria (78 isolates), other Gram-positive bacteria (13 isolates) and Gram-negative bacteria (11 isolates). A selection of 48 LAB isolates were further characterized and identified by phenotypic tests and SDS-PAGE electrophoresis of whole cell proteins. Selected clusters of LAB isolates were analysed by plasmid profiling, pulsed field gel electrophoresis and 16S rRNA gene sequencing. Enterococcus faecalis was identified in spoilage associations at 15 degrees C and 25 degrees C, and its metabolic activity corresponded to chemical changes in spoiled products. Carnobacterium divergens, a non-motile Carnobacterium sp. nov. and Lactobacillus curvatus were the LAB species observed in spoilage associations of products stored at 0 degrees C, 5 degrees C and 8 degrees C. CONCLUSIONS: Enterococcus spp. and Carnobacterium spp. were the dominant parts of spoilage associations of cooked and brined MAP shrimps stored at high and low temperatures, respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: The SDS-PAGE technique and simple biochemical keys allowed the majority of LAB isolates from spoilage associations of cooked and brined MAP shrimps to be identified at the species level.

Animals↗
PubMed1996

Influence of processing conditions on the release of sodium fluoride from oligomeric L-lactic acid matrices.

Matrices were prepared in the shape of rods with a diameter of 4 mm and a length of 10 mm. They were composed of oligomers of L-lactic acid (Mw 2550-11730 Daltons) and micronized sodium fluoride particles. Sodium fluoride concentration was kept in the range 5-60%. Matrices were prepared by melting the mixture of L-lactic acid oligomer and sodium fluoride. Two types of products according to the applied cooling rate were prepared and evaluated for release characteristics in vitro. Sink conditions of isotonic phosphate buffer solution pH = 7.4 at 37 degrees C were maintained throughout the experiment. The concentration of dissolved sodium fluoride was determined by ion-selective electrode. It was documented that the release rate of sodium fluoride is strongly dependent on the molecular weight of oligomer. The effects of sodium fluoride concentration and cooling rate of melted mixture were evaluated by ANOVA, separately for each oligomer. The effect of sodium fluoride concentration was significant at each oligomer studied, while the influence of cooling rate was significant with higher molecular weight oligomers. Moreover, this effect is ambiguous and dependent on the capability of oligomers to form crystalline phases and on the form and geometric arrangement of this phase.

Biocompatible Materials↗
PubMed1996

NAD-specific 6-phosphogluconate dehydrogenase in lactic acid bacteria.

6-Phosphogluconate dehydrogenase was screened in for cell-free extracts from seventeen strains of lactic acid bacteria. Three types of the enzyme could be classified according to the coenzyme specificity: NAD-specific, NADP-specific, and non-specific types. The two strains that had a heterofermentative pathways had an NAD-specific 6-phosphogluconate dehydrogenase. This type had higher enzyme activity per proteins in the cell-free extracts, and more specificity to NAD compared to the other types of the enzyme in the lactic acid bacteria studied.

Cell-Free System↗
PubMedDate not supplied

Acquired antibiotic resistance in lactic acid bacteria from food.

Acquired antibiotic resistance, i.e. resistance genes located on conjugative or mobilizable plasmids and transposons can be found in species living in habitats (e.g. human and animal intestines) which are regularly challenged with antibiotics. Most data are available for enterococci and enteric lactobacilli. Raw material from animals (milk and meat) which are inadvertantly contaminated with fecal matters during production will carry antibiotic resistant lactic acid bacteria into the final fermented products such as raw milk cheeses and raw sausages. The discovered conjugative genetic elements of LAB isolated from animals and food are very similar to elements studied previously in pathogenic streptococci and enterococci, e.g. theta-type replicating plasmids of the pAMbeta1, pIP501-family, and transposons of the Tn916-type. Observed resistance genes include known genes like tetM, ermAM, cat, sat and vanA. A composite 29,871 bp resistance plasmid detected in Lactococcus lactis subsp. lactis isolated from a raw milk soft cheese contains tetS previously described in Listeria monocytogenes, cat and str from Staphylococcus aureus. Three out of five IS elements on the plasmid are almost or completely identical to IS1216 present in the vanA resistance transposon Tn1546. These data support the view that in antibiotic challenged habitats lactic acid bacteria like other bacteria participate in the communication systems which transfer resistance traits over species and genus borders. The prevalence of such bacteria with acquired resistances like enterococci is high in animals (and humans) which are regularly treated with antibiotics. The transfer of antibiotic resistant bacteria from animals into fermented and other food can be avoided if the raw substrate milk or meat is pasteurized or heat treated. Antibiotic resistance traits as selectable markers in genetic modification of lactic acid bacteria for different purposes are presently being replaced, e.g. by metabolic traits to generate food-grade vectors.

Animals↗
PubMed1996

Predictive models of the effect of temperature, pH and acetic and lactic acids on the growth of Listeria monocytogenes.

The combined effect of temperature (1-20 degrees C), pH (4.5-7.2) and acetic acid (0-10,000 mg/l; model 1) or lactic acid (0-20,000 mg/l; model 2) on growth of Listeria monocytogenes in laboratory media was studied. Growth curves at various combinations of temperature, pH and acid concentration were fitted by the model of Baranyi and Roberts (1994), and specific growth rates derived from the curve fit were modelled. Predictions of growth from the models were compared with data in the literature, and this showed the models to be suitable for use in predicting growth of L. monocytogenes in a range of foods including meat, poultry, fish, egg and milk and dairy products. The two models are compatible, i.e. they give similar predictions for cases when no acid is present.

Acetic Acid↗
PubMed1993

Antigenotoxic properties of lactic acid bacteria in vivo in the gastrointestinal tract of rats.

In view of the high incidence of dietary-related tumors, one important research goal is to identify the participating genotoxic carcinogens and the nutritional factors that may counteract their activities. We therefore have further developed a method to assess DNA damage in tumor target tissues of the gastrointestinal tract. Subsequently the prevention of this inducible DNA damage by lactic acid bacteria and by milk products fermented with probiotics was studied as well. The microgel electrophoresis technique was applied to cells of the esophageal, gastric, duodenal, and colonic mucosa. Cells were grouped according to their degree of DNA damage, the simplest measure of which is to discriminate between those with damage (comets) and those without damage. When these cells were isolated from animals treated with a genotoxic carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and exposed to MNNG for 1-24 hours, it was possible to follow the course of genotoxicity throughout the gastrointestinal tract. After the animals were treated with the lactic acid bacteria under study, it was possible to detect antigenotoxic properties as well. The gavage of 10(10) viable Lactobacillus casei cells in 10 ml of 0.9% NaCl per kilogram body weight immediately before the oral administration of MNNG (5 mg/kg body wt) resulted in a reduction of induced DNA damage in gastric and colonic mucosa cells. A sequential treatment schedule was even more effective: when the animals were treated orally with lactic acid bacteria or yogurt (10 ml/kg body wt) in the morning followed by MNNG (7.5 mg/kg body wt) eight hours later and the colon cells were isolated 16 hours later, the percentages of cells remaining intact were distinctly higher in the combination groups (68 +/- 10 and 68 +/- 19 for L. casei and a "Bio" yogurt, respectively) than in the group receiving only MNNG (45 +/- 17). The effect of heating L. casei was studied and was found to yield less clear-cut effects in preventing genotoxicity. The method is an efficient tool to elucidate antigenotoxic properties of food components in vivo in those target tissues actually afflicted by dietary-related tumors.

Animals↗
PubMed2002

Thermophilic production of lactic acid using integrated membrane bioreactor systems coupled with monopolar electrodialysis.

The thermophilic Bacillus strain BS119 was selected for this study to demonstrate the long term performance of lactic acid production and simultaneous pre-purification. Integrated continuous cell recycle cultivation using ultra-filtration membrane bioreactor (MBR) systems was investigated. The permeate from the MBR was routed to an on-line electrodialysis (ED) to recover, pre-purify and concentrate lactate. The cultivation and ED was operated at 60 degrees C for more than 1,000 h at a pH of 6.5. At lower dilution rate (0.02 h(-1)), lactate concentration reached a maximum of 55 g l(-1) with clearly lower residual glucose levels. At 0.04 h(-1), lactate concentration was significantly lower at 35 g l(-1). Maximal volumetric productivities of 1.38 g l(-1) h(-1) were achieved. Under stable conditions, lactic acid yield on consumed glucose appeared stable at around 80%. It could be demonstrated that the addition of supplements like yeast extract and peptone severely influences product formation. Integration of mono-polar ED with the MBR systems yields lactate solutions with concentrations of up to 115 g l(-1). Because of the low substrate feed concentrations (less than 50 g l(-1)), lactate flux was rather poor, reaching a low maximum of 140 g m(-2) h(-1); nevertheless, stack energy consumption was positive with an average of 0.49 kWh kg(-1) lactate.

Bacillus↗
PubMed1999

[Observation of the biodegradation of domestic poly-DL-lactic acid plates in vivo]

OBJECTIVE:To analyze the degradation and related factors of domestic poly-DL-lactic acid(PDLLA) plates in vivo. METHODS: The artifical transverse fractures in mandibular bodies of dogs were created and internal fixed with domestic PDLLA plates as experimental group,the implanted PDLLA plates in femurs as control.A certain time after the operation,the plates in fractured and implanted regions were collected and undertaken macroscopy and scanning electromicroscopy(SEM),meanwhile the fracture-healing status was evaluated. RESULTS: With time going on,the surface of domestic PDLLA plates y and density of micro-holes among poly-DL-lactic acid molecules in the PDLLA plates increased gradually.16-20 weeks Domestic PDLLA plates can be gradually biodegradation in vivo,in which it is correspondent with and accelerative the fracture-healing process.

Journal Article↗
PubMedDate not supplied

[Adhesion of lactic acid bacteria to epithelium of different cavities of the human organism].

During investigation of adhesive properties of lactic acid bacteria it was found out that 11 strains adhered to buccal intestinal and vaginal epithelium of human. The highest adhesive activity was detected in enterococci (adhesive index 7.75-14.26), lower one--in streptococci (6.40-9.16). In lactobacilli adhesive properties manifested in different ways: Lactobacillus acidophilus strains adhered more often to buccal epithelium (2.58-4.60) and rarely--to intestinal and vaginal. L. plantarum manifested high adhesive activity (8.03 -9.69) to buccal epithelium and lower one--to the rest of epithelium types. Monosaccharide composition of glycocalix of 6 strains of lactic acid bacteria was studied to understand the adhesion mechanism. It was shown that surface structures of this microorganism interact with plant lectins, specific to certain monosaccharides.

Bacterial Adhesion↗
PubMed1993

Low molecular weight proteins as carriers for renal drug targeting: naproxen coupled to lysozyme via the spacer L-lactic acid.

Low molecular weight proteins (LMWPs) are potential carriers for targeting drugs to the kidney. To test whether ester bonds are suitable for the reversible drug conjugation, the antiinflammatory drug naproxen (Nap) was conjugated to the LMWP lysozyme (LYSO) via an ester bond using an L-lactic acid spacer (Nap-lact-LYSO, 1:1:1). The distribution and degradation of the conjugate in rats were compared to those of an equimolar mixture of free drug and LMWP and of a directly coupled conjugate without spacer (Nap-LYSO). The plasma clearance of Nap-lact-LYSO closely resembled that of Nap-LYSO and LYSO itself. Its major accumulation site appeared to be the kidney as demonstrated by extracorporal gamma-camera counting of the LMWP. Renally released naproxen was excreted in the urine as 6-desmethyl-naproxen-sulfate (6-DMN-S). Apparently the kidneys represent the main sites of demethylation and sulfation after administration of the LMWP-coupled drug. In addition, the renal excretion of naproxen (including its metabolites) was significantly delayed and sustained as compared to that after injection of uncoupled naproxen. Using the L-lactic acid spacer LMWP conjugation, the renal selectivity of Nap was increased 5.6 +/- 0.41-fold. Additional in vitro studies with Nap-lact-LYSO revealed that renal generation of the parent drug coincided with formation of low molecular weight catabolites, mainly as naproxen-L-lactic acid-lysine (Nap-lact-Lys). This indicated that in vitro the rate of cleavage of the ester bond is significantly slower than digestion of the carrier backbone itself.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1977

Regulation of cyclic AMP level and lactic acid production in Ehrlich ascites tumor cells.

1. Quercetin (3.3',4',5,7-pentahydroxy flavone) at the concentration of 10(-4) M, as well as 2-10(-2) M theophylline and 1.5 - 10(-4) M prostaglandin E2 caused maximal rise of cyclic AMP in Ehrlich ascites tumor cells. 2. No additional increase of cyclic AMP level in these cells was found when both quercetin (10(-4) M) and theophylline (2-10(-2) M) were present in the incubation medium, while combination of quercetin (10(-4) M) and prostaglandin E2 (1.5 - 10(-4) M) has a synergistic effect on the level of cyclic AMP. 3. Degradation of cyclic AMP by homogenate of Ehrlich ascites tumor cells was inhibited by both quercetin and theophylline. 4. Quercetin, and to a smaller but significant extent theophylline, inhibited the lactic acid production in Ehrlich ascites tumor cells while prostaglandin E2 did not change the glycolytic rate in these cells. No synergistic inhibitory effect on lactic acid production was found when combinations of quercetin and prostaglandin E2, quercetin and theophylline or prostaglandin E2 and theophylline were tested. 5. Treatment of Ehrlich ascites tumor cells with dextran sulfate abolished the inhibitory effect of quercetin on lactic acid production, while the effect of the bioflavonoid on cyclic AMP levels was not altered.

Animals↗
PubMed1992

Transfer of lactic acid bacterial strains from the feed to the sow, the environment, and the piglets.

The spread of lactic acid bacterial strains to the environment and to newborn piglets was investigated after feeding of such strains to sows. Rifampicin resistant bacterial strains were fed to sows, 10(10) c.f.u. per day, during the period from 1 week before expected farrowing until 1 week after farrowing. Fecal samples from the sows and samples of litter were collected for bacteriological examination together with swabs from the pens, the skin of the sows, and from the rectum of the piglets. The test strains were only excreted in relatively low amounts in the feces of the sows, approximately 10(3)-10(6) c.f.u. per gram. They were not able to displace the normal lactic acid bacterial flora in the sows nor were they transmitted to the intestinal tract of the piglets to any significant extent. After the last administration the test strains disappeared from both feces, skin, and environment, indicating that no permanent colonization had taken place, although considerable differences in duration of persistence were noticed between test strains.

Animal Feed↗
PubMed2006

Searching for bacteriocin-producing lactic acid bacteria in soil.

A survey was conducted on the isolation and characterization of bacteriocin-producing lactic acid bacteria in soil. Forty-two acid-producing bacterial strains were isolated from 55 soil samples collected in Yamanashi prefecture, Japan. Investigation of antibacterial activities of isolates revealed that three isolates, Lactobacillus animalis C060203, Enterococcus durans C102901 and Leuconostoc mesenteroides subsp. mesenteroides C060204, showed antibacterial activities against the indicator strain of Lactobacillus sakei JCM 1157T. Bacteriocin from Enterococcus durans C102901 showed different characteristics from the known durancin L28-1A, produced by Enterococcus durans L28-1. Furthermore, this is the first report of a bacteriocin being produced by Lactobacillus animalis. Viewing from the species, bacteriocins from strains C102901 and C060203 showed high possibilities for the novel substances. These significant findings suggest that soil may be a common source for the isolation of novel bacteriocin-producing lactic acid bacteria.

Anti-Bacterial Agents↗
PubMed1997

Erosion of biodegradable block copolymers made of poly(D,L-lactic acid) and poly(ethylene glycol).

Biodegradable block copolymers made of poly(ethylene glycol) monomethylether (Me.PEG) and poly(D,L-lactic acid) (PLA) were investigated for their erosion properties. Wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) investigations prior to erosion revealed that despite the low content of crystallizable Me.PEG of 10%, Me.PEG5-PLA45 is a partially crystalline polymer. The erosion of the polymer was investigated using cylindrical polymer matrix discs with a diameter of 8 mm and a height of 1.5 mm. WAXD and DSC spectra obtained from eroded polymer matrix discs suggest that both polymer blocks separate completely during erosion. The crystallinity of Me.PEG5-PLA45 was found to increase during erosion, which is probably due to the improved mobility of Me.PEG inside the polymer with a progressive degree of degradation. The erosion kinetics were found to be similar to that of PLA or poly(lactic-co-glycolic acid). During erosion the polymer matrix weight of dried samples remains constant for 11 weeks after which erosion sets in rapidly. From this observation one can conclude that the impact of the relatively small Me.PEG chains on Me.PEG5-PLA45 erosion is not pronounced. This is beneficial for all those applications that require the stability of the polymer matrix and in which the Me.PEG chain is intended to bring about other effects such as the modification of the surface properties of PLA polymers.

Biocompatible Materials↗
PubMed1973

Effect of selected lactic acid bacteria on growth of Staphylococcus aureus and production of enterotoxin.

Representative strains of 15 species of lactic acid bacteria were examined for their ability to influence growth of Staphylococcus aureus and production of enterotoxin in associative culture. Among the organisms used as effectors the streptococci were most inhibitory, followed by Pediococcus cerevisiae. The lactobacilli and Leuconostoc citrovorum were not inhibitory to growth and only slightly inhibitory to production of enterotoxin. Enterotoxin was detected in all cultures in which the population of S. aureus reached 8 x 10(7) per ml. At lower S. aureus populations no enterotoxin was detected after incubation for 48 h. Mechanisms of inhibition of growth and enterotoxin production by S. aureus strain 243 grown in association with Streptococcus lactis A64 or P. cerevisiae 10791 in APT broth were investigated. Competition for vital nutrients, especially niacin and biotin, and probably production of hydrogen peroxide contribute to inhibition. Production of lactic acid appears to inhibit growth of S. aureus in the early but not the late stages of incubation.

Bacteriological Techniques↗
PubMed2002

A food-grade cloning vector for lactic acid bacteria based on the nisin immunity gene nisI.

A new food-grade cloning vector for lactic acid bacteria was constructed using the nisin immunity gene nisI as a selection marker. The food-grade plasmid, pLEB 590, was constructed entirely of lactococcal DNA: the pSH 71 replicon, the nisI gene, and the constitutive promoter P45 for nisI expression. Electroporation into Lactococcus lactis MG 1614 with 60 international units (IU) nisin/ml selection yielded approximately 10(5) transformants/ micro g DNA. MG 1614 carrying pLEB 590 was shown to be able to grow in medium containing a maximum of 250 IU nisin/ml. Plasmid pLEB 590 was successfully transformed into an industrial L. lactis cheese starter carrying multiple cryptic plasmids. Suitability for molecular cloning was confirmed by cloning and expressing the proline iminopeptidase gene pepI from Lactobacillus helveticus in L. lactis and Lb. plantarum. These results show that the food-grade expression system reported in this paper has potential for expression of foreign genes in lactic acid bacteria in order to construct improved starter bacteria for food applications.

Aminopeptidases↗
PubMed2006

Antimicrobial activity of lysostaphin and a Listeria monocytogenes bacteriophage endolysin produced and secreted by lactic acid bacteria.

The expression and secretion signals of the Sep protein from Lactobacillus fermentum BR11 were used to direct export of two peptidoglycan hydrolases by Lb. fermentum BR11, Lactobacillus rhamnosus GG, Lactobacillus plantarum ATCC 14917 and Lactococcus lactis MG1363. The production levels, hydrolytic and bacteriocidal activities of the Listeria monocytogenes bacteriophage N-acetylmuramoyl-l-alanine amidase endolysin Ply511 and the glycylglycine endopeptidase lysostaphin were examined. Buffering of the growth media to a neutral pH allowed detection of Ply511 and lysostaphin peptidoglycan hydrolytic activity from all lactic acid bacteria. It was found that purified Ply511 has a pH activity range similar to that of lysostaphin with both enzymes functioning optimally under alkaline conditions. Supernatants from lactobacilli expressing lysostaphin reduced viability of methicillin resistant Staphylococcus aureus (MRSA) by approximately 8 log(10) CFU/ml compared to controls. However, supernatants containing Ply511 were unable to control L. monocytogenes growth. In coculture experiments, both Lb. plantarum and Lb. fermentum synthesizing lysostaphin were able to effectively reduce MRSA cell numbers by >7.4 and 1.7 log(10)CFU/ml, respectively, while lactic acid bacteria secreting Ply511 were unable to significantly inhibit the growth of L. monocytogenes. Our results demonstrate that lysostaphin and Ply511 can be expressed in an active form from different lactic acid bacteria and lysostaphin showed superior killing activity. Lactobacilli producing lysostaphin may have potential for in situ biopreservation in foodstuffs or for prevention of S. aureus infections.

Anti-Bacterial Agents↗
PubMed1997

Lactic acid bacteria: hydrophobicity and strength of attachment to meat surfaces.

The hydrophobicity and strength of attachment of several lactic acid bacteria with antimicrobial activity were studied. Hydrophobicity was determined by bacterial adherence to hydrocarbons (BATH; octane or xylene), adhesion to nitrocellulose filters (NCF), salt aggregation test (SAT) and adherence to phenyl-Sepharose beads (PSB). The relative hydrophobicity of lactic acid bacteria depended markedly on the method used. No correlation between either SAT or BATH (octane) and strength of attachment (Sr value) existed. However, a significant relationship between strength of attachment and BATH (xylene), NCF and PSB, respectively, was observed, showing the highest correlation coefficient (r = 0.778) for BATH (xylene).

Ammonium Sulfate↗