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PubMedDate not supplied

Two-peptide bacteriocins produced by lactic acid bacteria.

Bacteriocins from lactic acid bacteria are ribosomally produced peptides (usually 30-60 amino acids) that display potent antimicrobial activity against certain other Gram-positive organisms. They function by disruption of the membrane of their targets, mediated in at least some cases by interaction of the peptide with a chiral receptor molecule (e.g., lipid II or sugar PTS proteins). Some bacteriocins are unmodified (except for disulfide bridges), whereas others (i.e. lantibiotics) possess extensive post-translational modifications which include multiple monosulfide (lanthionine) bridges and dehydro amino acids as well as possible keto amide residues at the N-terminus. Most known bacteriocins are biologically active as single peptides. However, there is a growing class of two peptide systems, both unmodified and lantibiotic, which are fully active only when both partners are present (usually 1:1). In some cases, neither peptide has activity by itself, whereas in others, the activity of one is enhanced by the other. This review discusses the classification, structure, production, regulation, biological activity, and potential applications of such two-peptide bacteriocins.

Amino Acid Sequence↗
PubMed1999

Synthesis and properties of poly(lactic acid).

Poly(D,L lactic acid) was prepared by bulk polymerization of D,L lactide, both under atmospheric pressure and in vacuum. The obtained polymeric products were characterized in terms of molecular weight, Mw, melting point, calorimetric response and swelling behaviour. All products were amorphous. Their molecular weights were determined by viscosimetry and ranged from 2x10(3) to 9x10(4). Similarly, the melting points ranged from 90 to 210 degrees C. Swelling experiments, with specimens immersed in buffer solutions, showed that hydrolytic degradation started in a few days for the low Mw material, whereas for the higher molecular weight products it took much longer and probably followed a two-stage mechanism. This study suggests that the high molecular weight material could be an interesting carrier for the preparation of controlled release products, in cases where prolonged delivery is necessary.

Journal Article↗
PubMed1993

Levels of lactic acid in normal Indians & its relation to food, glucose, cholesterol, raised blood urea.

1. The level of lactic acid was found to be between 5mg 25mg percent in 95 percent in 186 normal Indias. There was no difference due to sex and age. 2. Level of lactic acid was estimated in blood of normal persons and diabetes type II patients to observe the effects of food and glucose. The effect of food and and glucose was to take the levels of lactic acid to higher level than normal in about 25 percent of persons examined. 3. Hyperglycemia of over 300 mg raised the blood lactic acid in 25 percent of patients. 4. Lactic acid was not affected by hypercholereteremia but was raised in 60 percent of cases with high blood urea.

Adolescent↗
PubMedDate not supplied

Blood lactic acid levels after artificial heart implantation.

The aim of this study is to investigate blood lactic acid levels after the placement of the AbioCor implantable replacement heart to determine whether circulatory support with the AbioCor device results in adequate tissue perfusion. Tissue perfusion may not be adequate during cardiac surgery, especially with the use of cardiopulmonary bypass (CPB). Inadequate perfusion is usually associated with anaerobic metabolism, metabolic acidosis, and lactate accumulation. Ten calves had implantation of the AbioCor by means of a right thoracotomy. Standard cardiopulmonary bypass was performed during surgery. Lactic acid levels and blood gas analyses were measured. All animals were monitored for pressures in the aorta, pulmonary artery, and left and right atria. The output of the AbioCor was calculated based on beat rate and stroke volume. All animals were rapidly weaned off cardiopulmonary bypass to full AbioCor support and had normal hemodynamics with normal filling pressures. The lactic acid levels were elevated after surgery, peaked at 8 to 12 hours, and then gradually decreased to the normal range 24 hours after surgery. There was a positive relationship between lactate levels, oxygen consumption, and extraction rate, that is, the lactic acid levels were higher in the presence of increased oxygen consumption and increased oxygen extraction rate. There was a negative relationship between lactate levels and oxygen delivery, and arterial and venous oxygen content, that is, the lactic acid levels were higher when oxygen delivery and arterial and venous oxygen contents were low. The pathophysiology of lactic acidosis is uncertain, but is most likely due to inadequate perfusion during cardiopulmonary bypass, and lactate washout after adequate perfusion has been established. The return to aerobic metabolism with clearance of lactate demonstrates that the AbioCor is able to provide complete circulatory support with normal tissue perfusion.

Acidosis, Lactic↗
PubMed1976

Comparison of self-selected recovery methods on lactic acid removal rates.

The purpose of this study was to compare lactic acid removal rates during three modes of recovery from a standardized exercise bout. Each subject (N = 6) completed a 1 mile run (92.2 +/- 3.7% Vo2max). Thereafter, lactic acid removal rates were compared in the runners at each of three different modes of recovery: a) rest; b) a self-selected, continuous jogging pace (free-jogging); and c) completely uncontrolled recovery (free-intermittent) normally practiced by athletes. Venous blood samples were taken immediately after the mile run and every 5 min thereafter for 20 min. Data were expressed relative to the initial post-exercise blood sample (100%). Lactic acid removal was significantly faster during the free-jogging recovery than during the free-intermittent and the resting recoveries (P less than 0.001). Removal rates during the free-intermittent recovery were significantly faster than during the resting recovery (P less than 0.001). The results indicated that nearly optimal lactic acid removal rates were attained during the free-jogging recovery.

Adolescent↗
PubMed1992

The influence of the fullness of milk in the breasts on the concentration of lactic acid in postexercise breast milk.

The purpose of this study was to observe the influence of the fullness of breast milk in the breasts prior to exercise on the concentration of lactic acid in breast milk following exercise. Twenty-three lactating women were randomly assigned to Group E (n = 11), which nursed and/or collected as much of the breast milk as possible prior to maximal exercise, and Group F (n = 12), which did not nurse or collect milk at least two hours prior to maximal exercise. Milk was collected at rest preexercise and 10, 30, 60 and 90 minutes postexercise and was analyzed for concentrations of lactic acid. ANOVA demonstrated 1) a significant increase in lactic acid in the milk at all postexercise collections for both groups and 2) a significant group vs postexercise time interaction for lactic acid concentration in milk. These differences represented differences in 1) time to peak lactic acid concentrations in milk (Group F = 10 min; Group E = 30 min) and 2) time for postexercise decreases in lactic acid concentrations in milk. Thus, the state of fullness of milk in the breasts is a factor which affects the concentration of lactic acid in breast milk following maximal exercise.

Adult↗
PubMed1996

Genomic organization of lactic acid bacteria.

Current knowledge of the genomes of the lactic acid bacteria, Lactococcus lactis and Streptococcus thermophilus, and members of the genera Lactobacillus, Leuconostoc, Pediococcus and Carnobacterium, is reviewed. The genomes contain a chromosome within the size range of 1.8 to 3.4 Mbp. Plasmids are common in Lactococcus lactis (most strains carry 4-7 different plasmids), some of the lactobacilli and pediococci, but they are not frequently present in S. thermophilus, Lactobacillus delbrueckii subsp. bulgaricus or the intestinal lactobacilli. Five IS elements have been found in L. lactis and most strains carry multiple copies of at least two of them; some strains also carry a 68-kbp conjugative transposon. IS elements have been found in the genera Lactobacillus and Leuconostoc, but not in S. thermophilus. Prophages are also a normal component of the L. lactis genome and lysogeny is common in the lactobacilli, however it appears to be rare in S. thermophilus. Physical and genetic maps for two L. lactis subsp. lactis strains, two L. lactis subsp. cremoris strains and S. thermophilus A054 have been constructed and each reveals the presence of six rrn operons clustered in less than 40% of the chromosome. The L. lactis subsp. cremoris MG1363 map contains 115 genetic loci and the S. thermophilus map has 35. The maps indicate significant plasticity in the L. lactis subsp. cremoris chromosome in the form of a number of inversions and translocations. The cause(s) of these rearrangements is (are) not known. A number of potentially powerful genetic tools designed to analyse the L. lactis genome have been constructed in recent years. These tools enable gene inactivation, gene replacement and gene recovery experiments to be readily carried out with this organism, and potentially with other lactic acid bacteria and Gram-positive bacteria. Integration vectors based on temperate phage attB sites and the random insertion of IS elements have also been developed for L. lactis and the intestinal lactobacilli. In addition, a L. lactis sex factor that mobilizes the chromosome in a manner reminiscent to that seen with Escherichia coli Hfr strains has been discovered and characterized. With the availability of this new technology, research into the genome of the lactic acid bacteria is poised to undertake a period of extremely rapid information accrual.

Bacteriophages↗
PubMed1983

Proteolytic systems in lactic acid bacteria.

The proteolytic systems of lactic acid bacteria are important as a means of making protein and peptide N available for growth and as part of the curing or maturation processes which give foods their characteristic rheological and organoleptic properties. The proteolytic systems of lactic acid bacteria are described in relation to their growth and their functions in protein-rich foods. Their role in the manufacture of milk products is discussed.

Amino Acids↗
PubMed1988

Lactic acid inhibition of gap junctional intercellular communication in in vitro astrocytes as measured by fluorescence recovery after laser photobleaching.

Lactic acid can permeate plasma membranes, causing intracellular acidosis. Gap junctions are sensitive to pHi and can be reversibly uncoupled by weak acids. In this study, dye coupling between in vitro astrocytes, presumably mediated by gap junctions, was measured in the absence and presence of lactic acid. Fluorescence recovery after laser photobleaching (gap-FRAP analysis) was used to measure dye coupling. Astrocytes bathed in Eagle's minimum essential medium (EMEM) with lactic acid, pHo 5.5-6, showed no difference in their dye coupling (mean recovery of fluorescence 30%) when compared to control astrocytes (mean recovery of fluorescence 26%). However, 24 mM lactic acid in EMEM, pHo 4.5, decreased dye coupling (mean recovery of fluorescence 2.0%). This effect occurred within 5 min of treatment. When lactic acid-EMEM, pH 4.5, was removed from astrocytes after 30 min and the cells were incubated in EMEM for 24 hr, decreased coupling was not reversed (mean recovery 4.0%). When lactic acid-treated astrocytes were incubated in EMEM for 48 hr, the mean recovery of fluorescence increased to 15% (i.e., 42% of the recovery seen in controls). These observations suggest that brief exposure to high concentrations of lactic acid can have immediate and long-lasting effects on glial gap junctional communication. Under pathological circumstances, such a sequence could be initiated, and this might impair astrocytic control of the central nervous system microenvironment mediated by spatial buffering.

Animals↗
PubMed1993

Antimicrobial activity of ethanol, glycerol monolaurate or lactic acid against Listeria monocytogenes.

Minimal inhibitory concentrations (MIC) and antimicrobial effects of glycerol monolaurate (monolaurin), ethanol and lactic acid, either alone or in combination, against Listeria monocytogenes in tryptic soy broth were determined. Ethanol at concentrations up to 1.25% did not inhibit growth, but growth was strongly inhibited in the presence of 5% ethanol. MIC values of monolaurin and ethanol alone were 10 micrograms/ml (0.001%) and 50,000 micrograms/ml (5%), respectively. However, MIC values were not changed when monolaurin was combined with ethanol. When 5 micrograms/ml monolaurin was combined with 5% ethanol, the inhibitory effect of the combination was similar to the most active compound alone after 24 h incubation. These data indicate little interaction between monolaurin and ethanol against L. monocytogenes. MIC value of lactic acid alone was 5000 micrograms/ml (0.5%), but was lower when 1.25% ethanol was combined with 0.25% lactic acid. When 2.5% ethanol was combined with 0.25% lactic acid, the combination did not increase the inhibitory effect of the most active single compound alone. This result also indicates that there was little interaction between ethanol and lactic acid.

Culture Media↗
PubMed2004

Changes in galactose and lactic acid content of sweet whey during storage.

Whey is often stored or transported for a period of time prior to processing. During this time period, galactose and lactic acid concentrations may accumulate, reducing the quality of spray-dried whey powders in regard to stickiness and agglomeration. This study surveyed industry samples of Cheddar and mozzarella cheese whey streams to determine how galactose and lactic acid concentrations changed with storage at appropriate (4 degrees C) and abuse (37.8 degrees C) temperatures. Samples stored at 4 degrees C did not exhibit significant increases in levels of lactic acid or galactose. Mozzarella whey accumulated the greatest amount of galactose and lactic acid with storage at 37.8 degrees C. Whey samples derived from cheese made from single strains of starter culture were also evaluated to determine each culture's contribution to galactose and lactic acid production. Starter cultures evaluated included Streptococcus salivarius ssp. thermophilus. Lactobacillus helveticus, Lactobacillus delbrueckii ssp. bulgaricus, Lactococcus lactis ssp. cremoris, and Lactococcus lactis ssp. lactis. Whey derived from L. helveticus accumulated a significantly greater amount of lactic acid upon storage at 37.8 degrees C as compared with the other cultures. Galactose accumulation was significantly decreased in whey from L. lactis ssp. lactis stored at 37.8 degrees C in comparison with the other cultures. Results from this study indicate that proper storage conditions (4 degrees C) for whey prevent accumulation of galactose and lactic acid while the extent of accumulation during storage at 37.8 degrees C varies depending on the culture(s) used in cheese production.

Cheese↗
PubMed1988

Bacteriological quality of broiler carcasses as affected by in-plant lactic acid decontamination.

In an attempt to improve the bacteriological quality of broiler carcasses the bactericidal effect of treatments with 1% and 2% lactic acid was investigated. Bacterial colonisation was determined immediately after treatment, after the carcasses had been chilled and during storage at 0 degrees C. Examination included numbers of mesophilic aerobic and psychrotrophic aerobic colony-forming units (CFU), CFU of Enterobacteriaceae at 37 degrees C and CFU of Staphylococcus aureus. Immediately after treatment colonisation per gram skin was generally reduced by about 1 log. Initially 2% lactic acid was not found significantly more effective in reducing colony counts than 1%. However, treatment with 2% lactic acid suppressed post-decontamination colonisation with Enterobacteriaceae more effectively than 1% lactic acid, as determined after 15-18 days storage at about 0 degrees C. Lactic acid treatment was most effective when applied shortly before chilling. Successive treatment at three different stages during slaughtering did not increase reduction of colony counts. It is concluded that decontamination with 1-2% lactic acid at pH 2, when applied shortly before chilling, will markedly improve the bacterial safety and increase the refrigerated shelf life of broiler carcasses.

Animals↗
PubMed2001

In-Plant evaluation of a lactic acid treatment for reduction of bacteria on chilled beef carcasses..

The effectiveness of a lactic acid treatment consisting of spraying a 4% L-lactic acid solution (55 degrees C at source) on chilled beef carcasses to reduce bacterial populations was tested in a commercial slaughter environment. All carcasses had been treated with a proprietary decontamination treatment composed of a hot water spray followed by a lactic acid spray prior to chilling. Bacterial groups used to indicate reductions included aerobic plate count (APC), total coliform count, and Escherichia coli count, and samples were examined from the brisket, the clod, and the neck regions of 40 untreated and 40 treated carcass sides. Depending on the carcass surface region, APCs were reduced by 3.0 to 3.3 log cycles. Log coliform and E. coli counts were consistently reduced to undetectable levels. The small reductions observed for coliforms are attributable to counts on untreated carcasses already being near the lower detection limit of the counting method. The percentage of samples with detectable numbers of coliforms (positive samples) on untreated carcasses ranged from 52.5 to 92.5%, while 0.0% of the samples collected from treated carcasses contained detectable coliforms. Percent E. coli-positive samples ranged from 7.5 to 30.0% on untreated carcasses and 0.0% after treatment of carcass sides. These results indicate that a hot lactic acid spray with increased concentration and time of application may be effectively implemented for an additional decontamination treatment of chilled beef carcasses prior to fabrication.

Abattoirs↗
PubMed1996

A pilot study of lactic acid as an enamel and dentin conditioner for dentin-bonding agent development.

The purpose of this pilot study was to determine how lactic acid solution at various concentrations and etching times affected prepared human enamel and dentin surfaces and to assess whether it could be used in place of phosphoric or maleic acid as an etchant. The occlusal surfaces of extracted molar teeth were ground wet with 600-grit silicon carbide paper and treated with various aqueous solutions of lactic acid. Random samples were prepared for observation by scanning electron microscopy. The rest were used to determine shear bond strength of bonded dental composite cylinders. The micrographs revealed that lactic acid dissolved the smear layer with various degrees of etching and demineralization. The degree of smear layer and matrix removal was proportional to the concentration of the acid and the length of application time. A 20% lactic acid concentration applied for 10 seconds produced a clearly etched surface with minimal demineralization. A 30% concentration not only removed the smear layer and enlarged the dentin tubule orifices but also appeared to affect the collagen matrix. The shear bond strength to enamel treated with 50% lactic acid (17.5 +/- 1.5 MPa) and All-Bond 2 etchant (18.9 +/- 1.3 MPa) were not significantly different (p > 0.05). However, mean dentin bond strengths for all groups of lactic acid etchant and All-Etch etchant (10% phosphoric acid) were statistically similar.

Acid Etching, Dental↗
PubMed2000

Characterization of lactic acid formation and adenosine triphosphate consumption in calcium-loaded erythrocytes of broiler chickens.

The formation of lactic acid and consumption of adenosine triphosphate (ATP) were measured in erythrocytes from broiler and White Leghorn chickens with the goal of providing further evidence that lactic acid, a metabolite from glycolysis, is an etiological factor for sudden death syndrome (SDS) in broiler chickens. When loaded with Ca2+, erythrocytes exhibited increased lactic acid concentrations. The effect of Ca2+ loading was significantly faster in broiler erythrocytes. In the absence of adenosine used as an energy-yielding substrate, Ca2+ loading was followed by a reduction in ATP concentrations. The effect was also significantly faster in broiler erythrocytes. Intravenous injection of a 20% lactate solution at 0.1 mL/kg produced SDS-like death of broilers but not White Leghorns. The results obtained in erythrocytes indicate that, in broilers, a greater amount of energy is required for regulation of intracellular Ca2+ concentrations, and, thereby, formation of lactic acid is more accelerated. In addition to the result that intravenous lactate injection caused death in broilers, an elevation of lactic acid concentrations in blood, arising from operation of Ca2+ regulation mechanisms, may predispose broilers to incidence of SDS.

Adenosine Triphosphate↗
PubMed1984

Effect of aflatoxin B-1 on the proteolytic activity of some lactic-acid bacteria.

The proteolytic activity of five (ATCC) strains of lactic acid bacteria were investigated in the presence of different concentrations of aflatoxin B-1. The presented data revealed that aflatoxin in milk can affect the lactic acid bacteria which are used in the manufacture of dairy products. Such effect depends on toxin concentration and the species of lactic acid bacteria. This investigation is of practical value because it may explain the effect which occurs during cheese manufacture. This defect can be characterized by off flavour which can be very undesirable for a ripened cheese.

Aflatoxin B1↗
PubMed2004

Production of optically pure D-lactic acid by Nannochlorum sp. 26A4.

Microalgae were screened from seawater for greenhouse gas CO2 fixation and D-lactic acid production by self-fermentation and tested for their growth rate, starch content, and conversion rate from starch into D-lactic acid. More than 300 strains were isolated, and some of them were found to have suitable properties for this purpose. One of the best strains, Nannochlorum sp. 26A4, which was isolated from Sakito Island, had a starch content of 40% (dry weight), and a conversion rate from consumed starch into D-lactic acid of 70% in the dark under anaerobic conditions. The produced D-lactic acid showed a high optical purity compared with the conventional one. The proposed new D-lactic acid production system using Nannochlorum sp. 26A4 should also be an effective technology for greenhouse gas CO2 fixation and/or conversion into industrial raw materials.

Eukaryota↗
PubMed1958

A test for myocardial infarction; the present status of the use of serum lactic acid dehydrogenase.

Determination of the amount of lactic acid dehydrogenase in the blood has been demonstrated as a useful aid in the diagnosis of myocardial necrosis. The reliability of the test and the time element of the appearance and disappearance of the enzyme in the blood give it advantages over transminase determinations. In addition there appears to be a correlation of lactic acid dehydrogenase content with metastatic carcinoma. The levels of the substance correlate with the presence or absence of metastatic lesions and also with the extent of the metastasis. Few other clinical states are associated with increased levels of this enzyme, and in most instances the few that are can be excluded by other reliable criteria.

Carcinoma↗