Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LACTIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,639 records · Page 91Linked to original sources
PubMed1999

Effective use of nisin to control lactic acid bacterial spoilage in vacuum-packed bologna-type sausage.

Lactic acid bacteria (LAB) commonly cause spoilage in minimal heat-treated vacuum-packed cured delicatessen meats. Predominant species are Lactobacillus sake and L. curvatus. LAB strains isolated from spoiled products of this type (liver sausage, ham and bologna sausage) were found to be sensitive to low nisin concentrations (maximum of 1.25 microg g(-1)). Addition of 25 microg g(-1) nisin (as Nisaplin) inhibited the growth of LAB spoilage organisms inoculated into vacuum-packed pasteurized bologna-type sausages stored at 8 degrees C. Control sausages became spoiled (>10(8) LAB CFU g(-1)) by day 7, whereas sausages containing nisin remained unspoiled for >50 days. The effect of three types of phosphates (used as emulsifiers) on nisin activity in the sausages was compared. LAB growth rate was fastest in samples containing orthophosphate, and slowest in sausages containing diphosphate. The shelf life was also greatly extended in the latter. Fat content also affected nisin activity. Nisin activity (as indicated by LAB inhibition) was greatest in samples containing 15% > 25% > 37% (wt/wt) fat. In a sausage formulation containing 37% fat and incorporating diphosphate as emulsifier, levels of nisin as low as 2.5 microg g(-1) showed antibacterial effects. A nisin level of 6.25 microg g(-1) totally inhibited LAB growth for over 4 weeks and 25 microg g(-1) for 5 weeks. Spoilage control was achieved in the same sausage formulation but with 25% (wt/wt) fat; 12.5 microg g(-1) nisin prevented LAB growth for 5 weeks.

Animals↗
PubMed2001

The effects of cultivating lactic starter cultures with bacteriocin-producing lactic acid bacteria.

The effects of bacteriocins produced by six strains of lactic acid bacteria on 9 mesophilic and 11 thermophilic commercial starter cultures were investigated in mixed cultures of commercial starters with bacteriocin-producing strains in milk. The bacteriocins produced by the test organisms were nisin A, nisin Z, lacticin 481, enterocin AS-48, a novel enterocin, and a novel plantaricin. Mesophilic commercial starters were in most cases tolerant of bacteriocins, with only two of the starters being partially inhibited, one by four and the other by two bacteriocins. The aminopeptidase activities of mesophilic starters were generally low, and only one of the combinations of mesophilic starter-bacteriocin producer gave double the aminopeptidase activity of the starter culture without the bacteriocin producer. Thermophilic commercial starters were more sensitive to bacteriocins than mesophilic starters, with six thermophilic starters being partially inhibited by at least one of the bacteriocins. Their aminopeptidase activities were generally higher than those of the mesophilic starters. The aminopeptidase activities of seven thermophilic starters were increased in the presence of bacteriocins, by factors of up to 9.0 as compared with the corresponding starter cultures alone. Bacteriocin-producing strains may be used as adjunct cultures to mesophilic starters for the inhibition of pathogens in soft and semihard cheeses, because mesophilic starters are rather tolerant of bacteriocins. Bacteriocin producers may also be used as adjunct cultures to thermophilic starters of high aminopeptidase activity, more sensitive to lysis by bacteriocins than mesophilic starters, for the acceleration of ripening in semihard and hard cheeses.

Aminopeptidases↗
PubMed1991

Salt formation of lactic acid oligomers as matrix for sustained release of drugs.

The calcium and sodium salts of L- and D,L-lactic acid oligomers were obtained by immersion of the oligomer powders (weight average mol. wt 3000-10,000) in aqueous solutions of CaCl2 and NaCl, respectively, at room temperature (22 degrees C). The salt formation was analysed by atomic absorption measurement. The thermal properties, including glass transition temperature, melting temperature, and softening temperature, were altered by conversion of the terminal free acid of the oligomer to its salt. An in-vitro release test of an anti-cancer drug from the oligomer beads showed that the drug was released more rapidly from the beads prepared from the non-converted oligomers than those prepared from the salts when the release test was carried out in media containing no calcium and no sodium ions.

Calcium Chloride↗
PubMed1999

Synthesis and characterisation of poly(D,L-lactic acid)-idoxuridine conjugate.

A new polymeric prodrug was prepared coupling 5-iodo-2'-deoxyuridine (IDU) to poly(d,l-lactic acid) (PLA) via a succinic acid spacer. The PLA-IDU conjugate was characterised by thermal analysis, IR and 1H and 13C NMR spectroscopy. The IDU content (0.024 mequiv.g-1 of PLA) was consistent with the carboxylic acid endgroup present in the polymer sample (0.025 mequiv.g-1 of polymer). The PLA-IDU conjugate was susceptible to degradation in biological environments containing esterase, whereas IDU was not detected by chemical hydrolysis in pH 7.4 phosphate buffer. The conjugate should be used to prepare injectable microspheres and nanospheres containing IDU chemically coupled to the polymer carrier.

Animals↗
PubMed1999

High-performance liquid chromatographic assay of (+/-)-lactic acid and its enantiomers in calf serum.

Two high-performance liquid chromatographic methods are described for the determination of lactic acid and its enantiomers in calf serum. A 300x8.0 mm I.D. column packed with sulfonated styrene-divinylbenzene copolymer and a 50x4.6 mm ODS column with N,N-dioctyl-L-alanine were used. UV detection was at 205 and 236 nm for the non-chiral and chiral assays, respectively. Both assays demonstrated excellent linear relationships between peak area ratios and serum concentrations over a range of 0.5 to 20 mM, based on 100 microl bovine serum. Recovery was complete. Inter- and within-batch bias and relative standard deviation were <15%.

Animals↗
PubMed2002

Optimization of the separation lactic acid enantiomers in body fluids by capillary electrophoresis.

The optimization of the separation conditions of the two optical isomers of lactic acid by a factorial design is reported. Initially, different chiral selectors were systematically investigated and then a experimental design with three quantitative factors (cyclodextrin concentration and background buffer pH and concentration) were evaluated. Optimal conditions for obtaining a resolution higher than 1.5 were: phosphate buffer 200 mM at pH=6.0 with 413 mM 2-hydroxypropyl-beta-cyclodextrin added (HP-beta-CD), 20 degrees C, -20 kV of applied potential and polyacrylamide-coated capillary. The method was validated for the measurement in plasma and it was applied to the identification of both isomers in body fluids such as urine, amniotic fluid and cerebrospinal fluid. Samples were centrifuged and diluted (1:4) prior to the analysis.

Body Fluids↗
PubMed1998

Factors influencing the diffusion-controlled release of papaverine from poly (L-lactic acid) matrix.

Effects of drug content and medium pH on the release of papaverine (PAP) from biodegradable poly(l-lactic acid) [P(L)LA] matrix were investigated to reveal the predominant factors affecting the two-stage diffusion-controlled release mechanism. A drug-dissolved cylindrical matrix (rod; 10 mmx1 mm diameter) was prepared by heat compression method. In the case of a PAP content below 10%, pH was found to have a strong effect on the release rate, and drug content was found to have no effect on the release profile. The release profile consisted of two sequential diffusion stages due to P(L)LA transformation from amorphous to the semicrystalline state prior to release. In the first release stage PAP diffused through the swollen matrix. The release accelerated with increasing medium pH due to an increase in water content in the acidic P(L)LA rod. In the second release stage PAP diffused through the water-filled micropores developed as a result of the polymer crystallization. On the assumption that the drug partition between the polymer and the medium in the micropores affects the diffusion and the partition is controlled by pH, we derived a modified diffusion kinetic equation. The observation that the release decelerated with increasing medium pH can be explained by the derived equation as resulting from the increase in the drug partition to the polymer. In the case where the rods contained more than 15% of PAP, the drug precipitated out as crystals during release. Accordingly, these rods showed a slower release.

Chemical Phenomena↗
PubMed1995

An investigation on the role of plasma and serum opsonins on the internalization of biodegradable poly(D,L-lactic acid) nanoparticles by human monocytes.

We demonstrate here that polyethylene glycol (PEG) 6,000 protects biodegradable poly(D,L-lactic acid) nanoparticles (PLA NP) from extensive uptake by monocytes in plasma. These results are in agreement with those previously obtained with PEG 20,000 which reduced the uptake of PLA NP by human monocytes in phosphate buffered saline and plasma, and prolonged the NP circulation time in vivo. The coating efficiency of PEG 6,000 and 20,000 was substantially decreased in serum. The difference between the uptake of plain and coated NP clearly reappeared for PEG 20,000-coated NP in heat inactivated serum and in IgG-depleted serum. We suggest that typical plasma proteins, heat labile serum proteins (e.g. complement components) and IgG are involved in the opsonization of plain and coated PLA NP. Other proteins previously found to adsorb onto these NP, namely albumin and apolipoprotein E, did not appear to directly influence the uptake process.

Biodegradation, Environmental↗
PubMed2004

Nucleation and growth rates of poly(L-lactic acid) microparticles during precipitation with a compressed-fluid antisolvent.

We measured nucleation and growth rates of poly(L-lactic acid) (PLLA) microparticles produced during precipitation with a compressed-fluid antisolvent (PCA). The injector/precipitator used in this study satisfied the constraints and assumptions incorporated in the development of the mixed-suspension, mixed-product-removal population balance theory. A semicontinuous operation mode with batch product filtering was developed, and results from product particle size distributions allowed nucleation and growth rates to be determined through the use of population balances. Kinetic data, obtained by operating the precipitator under various degrees of supersaturation and suspension density, were used to generate a nucleation rate model for PLLA. Model results indicate a relative kinetic order of 1 and a linear dependence of the nucleation rate on the suspension density. First-order dependence of the nucleation rate on suspension density suggests secondary nucleation mechanism(s) are operative within this PCA flow system and may explain the relative insensitivity of particle size distributions to changes in PCA operating conditions.

Carbon Dioxide↗
PubMed1996

Attachment of lactic acid bacteria to beef-muscle surfaces.

The effect of immersion time and cell concentration in the attachment of several lactic acid bacteria with antibacterial activity to beef-muscle surface was studied. The number of firmly attached bacteria increased with immersion time in the case of Pediococcus acidilacti, Lactobacillus sake, Lactococcus cremoris (two strains) and Pediococcus acidilacti. Pediococcus pentosaceus, Lactococcus lactis and Lactobacillus curvatus reached maximum adhesion after 15-30 min. The highest strength of attachment (Sr values) were observed after 15-30 min of contact time except for P. pentosaceus. For all strains, the number of bacteria adhering to meat increased with increasing cell concentration in the adhesion medium. The highest strength of attachment was observed at a cell concentration of 10(5)/mL mainly for L. sake, L. lactis and L. cremoris. Due to their attachment characteristics, L. sake, L. lactis and L. cremoris are proposed as potential biocontrol agents because they could grow on meat surface and limit the potential attachment of pathogenic microorganisms.

Animals↗
PubMed2004

Physical characterization of coupled poly(lactic acid)/starch/maleic anhydride blends plasticized by acetyl triethyl citrate.

Acetyl triethyl citrate (ATC) was used as a plasticizer for poly(lactic acid) (PLA)/starch blends coupled with maleic anhydride and an initiator of 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (L101). Elongation of the blend at break was markedly increased when the ATC content was above the 8% loading level, which is referred to as the percolation threshold. The extended elongation was achieved at the expense of tensile strength and elastic modulus. Thermal transitions of the blend, including the glass transition temperature (T(g)), cold crystallization temperature (T(c)) and melting temperature (T(m)), decreased with ATC content. Thermally induced ATC migration affected the thermal behavior of the plasticized blends and reduced elongation and tensile strength, whereas the elasticity modulus increased. ATC migration increased with ambient temperature, which was controlled by the activation energy of the blend system. Leaching of ATC was slow at room temperature in distilled water, but significant in boiling water. Additionally, the leaching rate was also directly proportional to the ATC content of the blend. Glass transition temperatures of PLA/starch/MA/L101 blends with various acetryl triethyl citrate contents.

Citrates↗
PubMed1998

Peroral administration of 14C-poly(D,L-lactic acid) nanoparticles coated with human serum albumin or polyvinyl alcohol to guinea pigs.

Biodegradable 14C-poly(D,L-lactic acid) (PLA50) nanoparticles coated either with a readily digestible protein albumin or with a non-digestible coating agent, polyvinyl alcohol (PVA), were prepared by the solvent evaporation technique. The nanoparticles were administered perorally to guinea pigs to evaluate the gastro-intestinal degradation of their PLA50 matrix. In the case of PLA50 nanoparticles coated with digestible albumin, substantial gastro-intestinal degradation of the PLA50 matrix occurred, leading to the passage of considerable amount (> or =45%) of water-soluble products across the gastrointestinal barrier. When a non-digestible coating agent like PVA was used, the degradation of the PLA50 matrix in the gastro-intestinal tract was at least two times lower (> or =19%). The results show that it is possible to control the in vivo degradation of PLA50 nanoparticles using appropriate coating agents. The present investigations showed a good correlation between previously observed in vitro results and the in vivo findings.

Animals↗
PubMed1993

Two Uptake Systems for Fructose in Lactococcus lactis subsp. cremoris FD1 Produce Glycolytic and Gluconeogenic Fructose Phosphates and Induce Oscillations in Growth and Lactic Acid Formation.

Fructose transport in lactococci is mediated by two phosphotransferase systems (PTS). The constitutive mannose PTS has a broad specificity and may be used for uptake of fructose with a fructose saturation constant (K(Fru)) of 0.89 mM, giving intracellular fructose 6-phosphate. The inducible fructose PTS has a very small saturation constant (K(Fru), <17 muM), and the fructose 1-phosphate produced enters the Embden-Meyerhof-Parnas (EMP) pathway as fructose 1,6-diphosphate. Growth in batch cultures of Lactococcus lactis subsp. cremoris FD1 in a yeast extract medium with fructose as the only sugar is poor both with respect to specific growth rate and biomass yield, whereas the specific lactic acid production rate is higher than those in similar fermentations on other sugars metabolized via the EMP pathway, e.g., glucose. In fructose-limited chemostat cultures, the biomass concentration exhibits a strong correlation with the dilution rate, and starting a continuous culture at the end of a batch fermentation leads to large and persistent oscillations in the biomass concentration and specific lactic acid production rate. Two proposed mechanisms underlying this strange growth pattern follow. (i) Fructose transported via the fructose PTS cannot be converted into essential biomass precursors (glucose 6-phosphate or fructose 6-phosphate), because L. lactis subsp. cremoris FD1 is devoid of fructose 1,6-diphosphatase activity. (ii) The fructose PTS apparently produces a metabolite (presumably fructose 1-phosphate) which exerts catabolite repression of both mannose PTS and lactose PTS. Since the repressed mannose PTS and lactose PTS are shown to have identical maximum molar transport rates, the results indicate that it is the general PTS proteins which are repressed.

Journal Article↗
PubMed1999

Lactic acid production by immobilized Lactobacillus casei in recycle batch reactor: a step towards optimization.

Different nutritional and process parameters influencing lactic acid production by Lactobacillus casei, adsorbed to Poraver beads in a recycle batch reactor system, were studied in an attempt to set up a system having a long operational lifetime and permitting use of high substrate concentrations for maximal conversion to the product. The presence of lactose, even as a minor fraction of the total sugar amount, was necessary for complete utilization by the organism for growth and conversion to lactate. Hydrolysed whey protein constituted a richer source of nitrogen compared to yeast extract. Addition of lactate to the medium at the start of the process resulted in severe inhibition compared with the normal process. For a homofermentative process, pH 6.0 was found to be optimal. The overall productivity of the recycle system was higher under all conditions studied in comparison with the batch process using free cells. Enhancement in productivity in the recycle batch reactor was also accompanied by an increase in density of suspended cells. However, the contribution of the suspended cells to the overall reactor productivity was not noticeable. The bead size of the matrix was found to be important for operational stability of the reactor.

Hydrogen-Ion Concentration↗
PubMed2005

Antibacterial activity of lactic acid bacteria included in inoculants for silage and in silages treated with these inoculants.

AIMS: To determine antibacterial activity in lactic acid bacteria (LAB) silage inoculants and in wheat and corn silages which were treated with these inoculants. METHODS AND RESULTS: Wheat and two corn silages were prepared in 0.25 l sealed glass jars. Inoculant treatments were prepared for each type of silage with each of 10 LAB silage inoculants at inoculation rate of 10(6) CFU g(-1). Untreated silages served as controls. Antibacterial activity was determined in the inoculants and in their respective silages with Micrococcus luteus and Pseudomonas aeruginosa. Antibacterial activity was detected in nine of the 10 inoculants whereas such activity in the silages varied. Control silages did not have antibacterial activity. CONCLUSIONS: Many LAB silage inoculants have antibacterial activity and in some cases this activity is imparted on inoculated silages. SIGNIFICANCE AND IMPACT OF THE STUDY: This study was conducted as part of a broader research objective, which is to find out how LAB silage inoculants enhance ruminant performance. The results of this study indicate that LAB silage inoculants produce antibacterial activity, and therefore, have a potential to inhibit detrimental micro-organisms in the silage or in the rumen.

Agriculture↗
PubMed1985

Influence of tissue lactic acid and ATP levels on postischemic recovery in rabbit skeletal muscle.

The effect of energy substrate depletion and of high lactic acid (LA) load on the development of irreversible cell injury was evaluated in the lateral gastrocnemius muscle of rabbits subjected to 4 hr of tourniquet hindlimb ischemia. Three groups of animals were studied. Group I, high ATP-ischemia, these animals were subjected to 4 hr of ischemia; group II, low ATP--low LA ischemia, in this group the gastrocnemius muscle was electrically stimulated for 5 min during ischemic conditions to reduce the glycogen store, a short reperfusion period was allowed after the stimulation in order to wash out the built up LA, and the muscle was then subjected to 4 hr of ischemia; group III, low ATP--high LA ischemia, in this group glycogen was depleted as in group II, but no reperfusion period was allowed before the 4 hr period of ischemia. In group I, ATP levels were well preserved during the ischemic period, whereas in the substrate-deprived groups (II and III) a rapid depletion of ATP and phosphocreatine (CP) occurred. The LA was twice as high in the "high LA" group (III) as in the "low LA" group (II) during the ischemic period. The extent of injury was evaluated after 24 hr of reperfusion by measuring ATP and CP content, and contractile force and by light microscopy. No or minor cell damage was found in group I. In group III--high LA--no recovery was obtained in any of the variables used for evaluation. In group II--Low LA--there was a certain recovery. ATP and CP increased to about 35% and contractile force to 25% of control. Morphologically about 20% of the muscle cells appeared to be unaffected by the ischemic insult. It is concluded that reduction of the glycogen available for ATP resynthesis during the ischemic period drastically reduces the ability of skeletal muscle to withstand prolonged ischemia. A high LA load seems to amplify the deleterious effects of a low initial substrate level.

Adenosine Triphosphate↗
PubMed2005

Yeast and lactic acid flora of tej, an indigenous Ethiopian honey wine: variations within and between production units.

A total of 200 samples of tej, an indigenous Ethiopian honey wine, were collected from ten production units at different production times. The samples were analysed for their microbial flora. Mean counts of aerobic mesophilic bacteria and aerobic spores for the different production units were <3 log cfu/ml. Coliforms and other members of Enterobacteriaceae were below detectable levels basically due to the low pH of the samples (<4.0). Yeasts were among the dominant micro-organisms in all samples with mean counts of 6 log cfu/ml for all production units. Over 25% of the yeast isolates belonged to Saccharomyces cerevisiae followed by Kluyvermyces bulgaricus (16%), Debaromyces phaffi (14%) and K. veronae (10%). Yeast counts showed significant variation within samples of a production unit (CV>10%) and difference in counts among all samples was also significant (P<0.01). The lactic acid bacteria had counts of 6 log cfu/ml with a significant variation within samples of a production unit (CV>10%) or among all samples (P<0.01). In most production units, the heterolactics had higher counts than the homolactics. The lactic flora consisted of Lactobacillus, Streptococcus, Leuconostoc and Pediococcus species. The lactobacilli were, however, the most frequently encountered groups. In most of the samples, the lactic flora was dominated by two (49.5%) or three (46%) groups of lactic acid bacteria.

Colony Count, Microbial↗