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PubMed2002

Competitive inhibition of Listeria monocytogenes in ready-to-eat meat products by lactic acid bacteria.

Forty-nine strains of lactic acid bacteria (LAB), isolated from commercially available ready-to-eat (RTE) meat products, were screened for their ability to inhibit the growth of Listeria monocytogenes at refrigeration (5 degrees C) temperatures on agar spot tests. The three most inhibitory strains were identified as Pediococcus acidilactici, Lactobacillus casei, and Lactobacillus paracasei by 16S rDNA sequence analysis. Their antilisterial activity was quantified in associative cultures in deMan Rogosa Sharpe (MRS) broth at 5 degrees C for 28 days, resulting in a pathogen reduction of 3.5 log10 cycles compared to its initial level. A combined culture of these strains was added to frankfurters and cooked ham coinoculated with L. monocytogenes, vacuum packaged, and stored at 5 degrees C for 28 days. Bacteriostatic activity was observed in cooked ham, whereas bactericidal activity was observed in frankfurters. Numbers of L. monocytogenes were 4.2 to 4.7 log10 and 2.6 log10 cycles lower than controls in frankfurters and cooked ham, respectively, after the 28-day refrigerated storage. In all cases, numbers of LAB increased by only 1 log10 cycle. The strain identified as P. acidilactici was possibly a bacteriocin producer, whereas the antilisterial activity of the other two strains was due to the production of organic acids. There was no significant difference (P > 0.05) in the antilisterial activity detected in frankfurters whether the LAB strains were used individually or as combined cultures. Further studies over a 56-day period indicated no impact on the quality of the product. This method represents a potential antilisterial intervention in RTE meats, because it inhibited the growth of the pathogen at refrigeration temperatures without causing sensory changes.

Animals↗
PubMed1995

[Do objects have history? A meeting between Pasteur and Whitehead in a lactic-acid bath].

Did Pasteur discover, construct, invent lactic acid? This Gordian knot in social studies of the sciences is happily cut when the scene played out at Lille in 1857 is peopled with Whiteheadean conceptual characters. The Nature addressed by Pasteur does not speak the language of scientific utterances but neither is it mute; it is imbued with propositions. Insofar as Pasteur plays the character of a scientist, he is 'acted on' by a singular proposition -- "a tale that perhaps might be told," as Whitehead would say, but that will only be true or false if Pasteur manages to make a real world correspond to this proposition, a world capable of providing logical subjects, and thus offering proof to "whomever judges with impartiality." A hybrid-mediator-translator of Pasteurian and microorganismic propositions, the experimental environment "makes the event," in an encounter from which a new Pasteur and a new yeast emerge, partners of a new history.

Acids↗
PubMed1987

Effects of lactic acid on astrocytes in primary culture.

Excessive tissue lactic acidosis is considered to be detrimental to the central nervous system (CNS) and may adversely affect recovery from anoxia, ischemia, trauma and epilepsy. Since astrocytes are believed to play a role in pH regulation in the CNS, we studied the effect of this acid on primary astrocyte cultures. Cells exposed to lactic acid showed chromatin clumping, an increase of lipid and dense bodies, a loss of polyribosomal clusters, slightly increased cytoplasmic lucency, swollen mitochondria and tangled intermediate filaments. These alterations progressed with lower pH and longer exposure. Irreversible changes occurred one to two hours after exposure at pH 6; after 30 to 60 minutes (min) at pH 5.5 and after ten to 30 min at pH 5. Comparable results were obtained with the use of other weak acids indicating that the observed changes were due to increased hydrogen ion concentration rather than secondary to lactate per se. Additionally, various concentrations of lactic acid adjusted to identical pH produced similar morphologic alterations. Thus, while lactic acid caused marked and at times irreversible alterations in astrocytes, severe and prolonged acidosis was required to produce such injurious effects. This relative resistance of astrocytes to acidosis is in keeping with their potential role in pH regulation in brain.

Animals↗
PubMedDate not supplied

[The efficacy of the use of lactic acid lactobacterin enriched with zinc in the treatment of patients with celiac disease].

Zinc sulfate-enriched lactic acid lactobacterin was used in the combined treatment of 23 children with celiac disease, aged from 1 to 10 years. A group of 23 children with celiac disease who received lactic acid lactobacterin without zinc were used as control. The patients treated with lactobacterin containing zinc showed a higher increase in body mass, total protein and zinc levels in the blood serum and elevated activity of metalloenzymes-ceruloplasmin and cytochrome oxidase.

Bacteriocins↗
PubMed1992

Preparation of neurotensin analogue-containing poly(dl-lactic acid) microspheres formed by oil-in-water solvent evaporation.

This report describes the preparation of injectable microspheres containing a neurotensin analogue (NA), which is a hexapeptide with neurotensin activity. NA, a hydrophilic drug, was successfully entrapped into poly(dl-lactic acid) microspheres prepared by a novel oil-in-water solvent evaporation method. The preparation method was investigated with regard to the partition of NA into the oily phase and the rapid phase separation of the polymer. Successful entrapment was achieved with the following conditions: (1) an alkaline water phase, (2) addition of fatty acid salt in the oily phase, and (3) addition of a water-miscible solvent in the oily phase. Under these conditions, NA was completely entrapped into the microspheres at poly(dl-lactic acid):NA molar ratios of greater than 3.

Amino Acid Sequence↗
PubMed1995

Biodiversity of lactic acid bacteria from food-related ecosystems.

The diversity of lactic acid bacteria within a variety of food-related ecosystems was assessed and the strain as well as environment specific characteristics were investigated. The strains (108 in toto) were isolated from plant material, traditional fermented foods, dried marine algae, sea food, fungi as well as spoiled foods and beverages, and all were characterized to genus level. Lactobacillus strains dominated all ecosystems and contributed to 65% of the isolates while a further 13% consisted of Lactococcus strains, 12% of Leuconostoc strains, 5% of Pediococcus strains, and 5% of unidentified strains. Plant material was the most diverse ecosystem containing representatives from each of the genera as well as the majority of dextran and tyramine producers. Those strains able to grow at 45 degrees C as well as acid tolerant strains were predominantly isolated from traditional fermented beverages while halotolerant strains occurred mainly in sea food. Two bacteriocin producers but no histamine producers were isolated.

Bacteria↗
PubMed1964

EFFECT OF POLYAMINE STRUCTURE ON GROWTH STIMULATION AND SPERMINE AND SPERMIDINE CONTENT OF LACTIC ACID BACTERIA.

Guirard, Beverly M. (University of California, Berkeley), and Esmond E. Snell. Effect of polyamine structure on growth and spermine and spermidine content of lactic acid bacteria. J. Bacteriol. 88:72-80. 1964.-Growth from small inocula of six species of lactobacilli was stimulated by addition of spermine or spermidine to a defined medium; none of four streptococcal species showed this effect. Lactobacillus casei was stimulated to the greatest extent. Several homologues and analogues partially duplicated the growth-promoting effects of spermidine; one inactive homologue, N-(3-aminopropyl)-1,6-hexanediamine, competitively inhibited the growth response to spermidine and spermine, and reduced or eliminated the response to several weakly active compounds. A procedure for separation of spermine and spermidine, and their estimation by bioassay with L. casei, was developed and applied to the estimation of these compounds in bacterial cells. Both compounds are present in lactic acid bacteria in amounts much smaller (1 to 5%) than those found in Escherichia coli. Addition of spermine or spermidine to the growth medium results in large accumulations in the cells, and the two amines show limited interconvertibility. Putrescine does not increase the cell content of either spermine or spermidine. Presence of the inhibitor prevents accumulation of the growth-stimulating amines. The polyamines appear to fill at least two valuable roles in the cell, one relatively nonspecific in its structural requirements, and one filled only by spermine and spermidine or their nearest homologues. N-(3-aminopropyl)-1,6-hexanediamine appears to prevent the latter function by competition for an appropriate cellular receptor.

Amines↗
PubMed1990

The role of transmembrane pH gradients in the lactic acid induced swelling of astrocytes.

The swelling of astrocytes is an important component of the morbidity and mortality associated with ischemic brain trauma. In the ischemic brain, lactic acid levels rise dramatically with a concomitant acidification of the extracellular fluid. In this study we have measured the effects of elevated extracellular lactate and reduced extracellular pH (pHo) on astrocyte volume using the human astrocyte-derived cell line UC-11MG. Neither elevated lactate nor reduced pHo alone increased cell volume, but swelling of about 25% was measured when the cells were exposed simultaneously to 20 mM lactic acid and a reduced pHo of 6. The swelling was correlated with an approximately 4-fold increase in intracellular lactate as pHo was decreased from 8.0 to 6.0. As pHo was decreased intracellular pH also decreased, but much more slowly so that at acidic extracellular pH there was an inwardly directed proton gradient. The measured intracellular lactate concentrations closely followed the theoretical levels predicted by a model in which lactate transport is coupled to the inwardly directed proton gradient. Kinetic studies indicated that lactate transport is saturable with a Km of 3.8 mM, consistent with the model for facilitated cotransport of lactate with a proton or exchange of lactate for a hydroxyl ion. These data suggest that an important mechanism of postischemic astrocytic swelling is a proton driven, active accumulation of lactate to levels that result in a significant osmotic gradient of lactate at acidic pH.

Alanine↗
PubMed2003

Poly(D,L-lactic acid)-poly(ethylene glycol)-monomethyl ether diblock copolymers control adhesion and osteoblastic differentiation of marrow stromal cells.

Biodegradable polymers, such as poly(lactic acid) (PLA) and poly(lactic-coglycolic acid) (PLGA), are attractive materials for tissue engineering because of their degradative and mechanical properties, which permit scaffolds to be tailored to the individual requirements of different tissues. Although these materials support tissue development, their chemical properties offer no control of cell adhesion or function because their surfaces become immediately masked by adsorbing serum proteins when the materials come into contact with body fluids. Furthermore, adhesion proteins undergo conformational changes and a decrease in bioactivity when adsorbed to hydrophobic materials, such as PLA. To overcome these limitations, we modified the properties of PLA by synthesizing a diblock copolymer with poly(ethylene glycol) (PEG), which is known to reduce the amount of adsorbed proteins and to modify their conformation. By altering the PEG content of these diblock copolymers we were able to control the adsorption of adhesion proteins and, because cell adhesion takes place only in the presence of serum proteins, to control cell adhesion and cell shape. Marrow stromal cell differentiation to the osteoblastic phenotype was strongly improved on PEG-PLA compared with PLA, PLGA and tissue culture polystyrene and led to a 2-fold increase in alkaline phosphatase activity and mineralization.

Animals↗
PubMedDate not supplied

Simplex lattice design for the optimization of the microencapsulation of a water soluble drug using poly(lactic acid) and poly(lactide co-glycolide) copolymer.

An emulsion solvent evaporation technique was applied to prepare microspheres of nicotinic acid as a water soluble vitamin. Poly(lactic acid) of two molecular weights, 2000 and 100,000 and poly(lactide-co-glycolide) (50:50) of molecular weight 18,000 were used. A simplex lattice design with the aid of a computer program was applied to study the effect of the previously mentioned polymers on different characteristics of the prepared microcapsules. The studied characteristics included the yield, the percentage drug loading and the particle size of microcapsules. Microcapsules were examined by light microscope for particle size determination and by electron scanning microscope for surface morphology characterization. The release pattern of the drug from the microcapsules was evaluated on the basis of the burst effect, the rate of release and the extent of release after 24 h. A model equation was developed to be the best representation of the relationship between the above polymers and the measured characteristics. The goodness of fit of the developed equations was checked, both statistically and experimentally. The release of the drug from microcapsules mainly followed the Higuchi diffusion model. Polylactic acid of a molecular weight 100,000 had the most pronounced delaying effect on the release rate of the drug. However, polylactic acid of a molecular weight 2,000 showed the highest improvement effect on the yield and the drug loading characteristics of the microcapsules. Poly(lactide-co-glycolide) copolymer exhibited the lowest burst effect and the most steady drug release pattern.

Drug Compounding↗
PubMed2006

Pilibacter termitis gen. nov., sp. nov., a lactic acid bacterium from the hindgut of the Formosan subterranean termite (Coptotermes formosanus).

A previously undescribed anaerobic, heterofermentative, non-spore-forming, Gram-positive rod was isolated from the hindgut of the Formosan subterranean termite Coptotermes formosanus Shiraki. The DNA G+C content of this bacterium was 37.8 mol%. Sequence analysis of the 16S rRNA gene revealed that this organism is related to, but distinct from, several genera of lactic acid bacteria, principally several species of the genus Enterococcus. Phenotypic traits that serve to separate this organism from related genera include high levels of the cellular fatty acid C18 : 1omega9c and the production of ethanol along with lactic acid as fermentation products. Based on the collected phylogenetic and phenotypic evidence, it is proposed that the unknown organism represents a novel species in a new genus, Pilibacter termitis gen. nov., sp. nov. The type strain is TI-1T (= ATCC BAA-1030T = CCUG 49613T).

Animals↗
PubMedDate not supplied

[Free amino acids in milk containing different amounts of dry substances after its fermentation by lactic acid Streptococci].

The content of free amino acids in milk containing different amounts of dry substances (11.2, 16, 18%) was measured. An increase in the content of dry substances reduced the capacity of lactic acid streptococci to accumulate threonine, proline, alanine, tyrosine and elevated their capacity to accumulate serine, cystine, norleucine, phenylalanine. The content of free amino acids was much higher during continuous cultivation than at the end of the stationary phase.

Amino Acids↗
PubMed2005

Effect of fiber diameter on spreading, proliferation, and differentiation of osteoblastic cells on electrospun poly(lactic acid) substrates.

Electrospinning is a promising method to construct fused-fiber biomaterial scaffolds for tissue engineering applications, but the efficacy of this approach depends on how substrate topography affects cell function. Previously, it has been shown that linear, parallel raised features with length scales of 0.5-2 microm direct cell orientation through the phenomenon of contact guidance, and enhance phenotypic markers of osteoblastic differentiation. To determine how the linear, random raised features produced by electrospinning affect proliferation and differentiation of osteoprogenitor cells, poly(lactic acid) and poly(ethylene glycol)-poly(lactic acid) diblock copolymers were electrospun with mean fiber diameters of 0.14-2.1 microm onto rigid supports. MC3T3-E1 osteoprogenitor cells cultured on fiber surfaces in the absence of osteogenic factors exhibited a lower cell density after 7 and 14 days of culture than cells cultured on spin-coated surfaces, but cell density increased with fiber diameter. However, in the presence of osteogenic factors (2 mM beta-glycerophosphate, 0.13 mM L-ascorbate-2-phosphate), cell density after 7 and 14 days of culture on fiber surfaces was comparable to or exceeded spin-coated controls, and alkaline phosphatase activity after 14 days was comparable. Examination of cell morphology revealed that cells grown on fibers had smaller projected areas than those on planar surfaces. However, cells attached to electrospun substrates of 2.1 microm diameter fibers exhibited a higher cell aspect ratio than cells on smooth surfaces. These studies show that topographical factors designed into biomaterial scaffolds can regulate spreading, orientation, and proliferation of osteoblastic cells.

3T3 Cells↗
PubMedDate not supplied

Influence of the metabolism pathway on lactic acid production from hemicellulosic trimming vine shoots hydrolyzates using Lactobacillus pentosus.

Hemicellulosic hydrolyzates from trimming wastes of vine shoots were proposed as a carbon source for lactic acid production by Lactobacillus pentosus CECT-4023T (ATCC-8041). These hydrolyzates are composed mainly of glucose (12.0 g/L), xylose (17.5 g/L) and arabinose (4.3 g/L). Acetic acid, the main subproduct, started to be produced after all of the glucose was completely depleted, showing that the acetic acid coproduction came only from the xylose and arabinose consumption. In the absence of glucose, the L. pentosus pathway shifts from homo to heterofermentative. Thus, L. pentosus can be considered a facultative heterofermentative organism, degrading hexoses (glucose) via the Embden-Meyerhoff-Parnas pathway and pentoses (xylose and arabinose) via the phosphoketolase pathway. Hydrolyzates were vacuum evaporated to increase the initial sugars concentration up to 35.4 g/L of glucose, 52.3 g/L of xylose, and 13.0 g/L of arabinose. Under these conditions the lactic acid concentration reached 46.0 g/L (Q(P) = 0.933 g/L.h, Y(P/S) = 0.78 g/g; Y(P/S) theoretical = 91.7%) and a clear product inhibition was observed. Additional experiments with synthetic sugars, in the absence of inhibitory compounds, indicate that this inhibition must be attributed to the metabolic pathway but not to the inhibitory compounds present in the fermentation broth.

Carbohydrate Metabolism↗
PubMed2004

Potential of selected lactic acid bacteria to produce food compatible antifungal metabolites.

The aim of this study was to assess the potential of lactic acid bacteria to inhibit the outgrowth of some common food-spoiling fungi. Culture supernatants of 17 Lactic acid bacterial strains as well as of three commercial probiotic cultures were evaluated for antifungal activity using an agar-diffusion method. The method parameters were chosen in order to reveal compounds for potential use in food (bio)preservation. Thirteen strains showed antifungal activity of which five strains were very promising: Lactobacillus acidophilus LMG 9433, L. amylovorus DSM 20532, L. brevis LMG 6906, L. coryniformis subsp. coryniformis LMG 9196 and L. plantarum LMG 6907. Four of these five strains were further examined; it was found that the produced antifungal metabolites were pH-dependent. The exact chemical nature of these substances has not been revealed yet.

Antibiosis↗
PubMed2003

Performance evaluation of a model describing the effects of temperature, water activity, pH and lactic acid concentration on the growth of Escherichia coli.

A square root-type model for Escherichia coli growth in response to temperature, water activity, pH and lactic acid was developed by Ross et al. [Int. J. Food Microbiol. (2002).]. Predicted generation times from the model were compared to the literature data using bias and accuracy factors, graphical comparisons and plots of residuals for data obtained from both liquid growth media and foods. The model predicted well for 1025 growth rate estimates reported in the literature after poor quality or unrepresentative data (n=215) was excluded, with a bias factor of 0.92, and an accuracy factor of 1.29. In a detailed comparison to two other predictive modes for E. coli growth, Pathogen Modeling Program (PMP) and Food MicroModel (FMM), the new model generally performed better. The new model consistently gave better predictions than the other models at generation times </=5 h. Inclusion of the lactic acid term in the model is proposed to account for the consistently good performance of the model for comparisons to growth in meat, a parameter that is not explicitly included in the other models considered in the comparisons.

Cell Division↗
PubMed1999

Classification and characterization of lactic acid bacteria isolated from the intestines of common carp and freshwater prawns.

Fifty-four isolates of lactic acid bacteria were obtained from the intestines of the common carp (Cyprinus carpio) and freshwater prawns (Macrobrachium rosenbergii) in Nakorn-Pathom Province, Thailand. All isolates were Gram-positive and catalase-negative cocci that did not produce gas from glucose and formed dl or L(+) lactic acid only. Most isolates were able to grow in broth at pH 9.6, in 6.5% NaCl (w/v) and 40% (w/v) bile. These isolates were divided into six groups (A-F) by sugar fermentation patterns. Strains in the groups A, B, C, and D showed intergroup DNA homology values of above 73.8%, indicating that these groups were composed of a single species. Following phylogenetic analysis, strains E 1, E 7, and E 26 from groups A, E, and F were placed in the clusters of the genera Lactococcus, Pediococcus, and Enterococcus, respectively. The type strains of Lactococcus garvieae, Pediococcus acidilactici, and Enterococcus faecium were the most closely related species with E 1, E 7, and E 26 in the phylogenetic tree, respectively. The DNA-DNA hybridization results indicated that strains in groups A (including groups B, C, and D), E, and F could be identified as belonging to the species Lactococcus garvieae, Pediococcus acidilactici, and Enterococcus faecium, respectively. Lactococcus garvieae was the dominant member of the population, accounting for 90.7% of the isolates.

Journal Article↗