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PubMedDate not supplied

Structural study of poly(L-lactic acid) spherulites.

Spherulites of poly(L-lactic acid) (PLLA) and of its blends with atactic poly(3-hydroxybutyrate) (a-PHB, from 10 to 75 wt %) were investigated by microfocus X-ray diffraction using synchrotron radiation. Radial scans in 5 microm steps with 3 microm beam diameter were performed. In PLLA, tens of identical diffraction images were collected. The unit cell a-axis was radially oriented, and the other axes lacked any specific orientation. In contrast, all PLLA/a-PHB blends showed a periodic change of diffraction pattern with increasing distance from the spherulite center. In all cases, the a-axis lay along the radius, while the b- and c-axes rotated about a with a defined periodicity. The unit cell twisting frequency increased with a-PHB content and closely matched the band spacing observed by polarized optical microscopy, which changed from 250 to 60 microm when the amount of a-PHB increased from 10 to 75 wt %. Concomitantly, a gradual broadening of all X-ray reflections was observed.

Crystallization↗
PubMed1991

Bohr shift by lactic acid and the supply of O2 to skeletal muscle.

Conditions simulating changes during physical exercise were induced in erythrocytes to determine the resulting Bohr effect. Lactic acid was added to red cell suspensions and whole blood with initial 25 and 60% SO2, at 42 Torr PCO2, and temperatures of 20 and 37 degrees C. Changes in pH, PO2 and SO2 were measured. CO2 liberation from buffering lactic acid in the extracellular fluid and its diffusion into erythrocytes resulted in an exaggerated Bohr shift, if the gas could not escape from the liquid phase (closed system, 'muscle' conditions). PO2 at constant SO2 increased by up to 11.7%.mmol-1.L lactic acid. After reequilibration to initial PCO2 values (open system, 'lung' conditions) the Bohr shift decreased (remaining PO2 increase 0.7-1.4%.mmol-1.L) mainly caused by the reduced acidification. In addition, the Bohr coefficients (BC) under closed conditions were larger (-0.36 to -0.50) than after reequilibration (-0.20 to -0.38). This difference is attributed to a larger CO2 BC than fixed acid BC. These effects might be enhanced in vivo by temperature differences between muscle and lung, lowered nonbicarbonate buffering of blood and counter-current blood flow in muscle.

Adult↗
PubMed2002

Degradation of and drug release from a novel 2,2-bis(2-oxazoline) linked poly(lactic acid) polymer.

The degradation rate of poly(lactic acid) (PLA) is typically modified by copolymerization of the glycolide with lactide. In the present study, the degradation rate of PDLLA was modified by a novel linking of PLA with 2,2'-bis(2-oxazoline). This modification resulted in formation of a more rapidly degrading poly(ester amide) (PEA) for controlled drug release. The hydrolytic degradation of PDLLA and PEA films was studied in PBS (pH 7.4, USP XXIV, 37 degrees C); the resulting decrease in molecular weight was determined by size exclusion chromatography and the weight loss of films was measured. Drug releases of guaifenesin (mw 198.2), timolol (mw 332.4), sodium salicylate (mw 160.1) and FITC-dextran (mw 4400) from PDLLA and PEA films and microspheres were examined in PBS (pH 7.4, 37 degrees C). The degradation rate of PEA was substantially greater than that of PDLLA. The release profiles of all small model drugs (mw <332.4) from PDLLA films were biphasic or triphasic, while the release profiles of small model drugs from PEA films varied extensively. Due to the faster weight loss of PEA, FITC-dextran (mw 4400) was released substantially more rapidly from PEA microspheres than from PDLLA microspheres. In conclusion, all model drugs, except guaifenesin, were released faster from PEA preparations than from PDLLA preparations.

Biocompatible Materials↗
PubMed1986

Bicarbonate buffering of lactic acid generated during exercise.

The pattern of decrease in arterial bicarbonate concentration ([HCO3-]) during progressive incremental exercise was compared with that of the rise in arterial lactate ([La-]) to determine the degree of buffering of lactic acid by bicarbonate. A mathematical model was derived for the change in [HCO3-] beyond the lactate threshold. This was based on a log-log transformation of the data, a model previously found to provide a very good fit to the [La-]-O2 consumption (VO2) relationship. The results of the analysis of incremental exercise data from 10 subjects show that the decrease in [HCO3-] very nearly matches the increase in [La-]. However, it was found by comparing regression models that the correspondence between [HCO3-] and [La-] could be improved by assuming that the [HCO3-] decrease was delayed until the arterial lactate level had increased by approximately 0.4 meq/l. This result is compatible with the existence of buffering mechanisms in the cell which buffer the initial increase of lactic acid. Beyond this initial buffering, lactic acid appears to be buffered almost entirely by the bicarbonate buffer system.

Adult↗
PubMedDate not supplied

Uniaxial drawing and mechanical properties of poly[(R)-3-hydroxybutyrate]/poly(L-lactic acid) blends.

Blends of poly(L-lactic acid) (PLLA) with two kinds of poly[(R)-3-hydroxybutyrate] (PHB) having different molecular weights, commercial-grade bacterial PHB (bacterial-PHB) and ultrahigh molecular weight PHB (UHMW-PHB), were prepared by the solvent-casting method and uniaxially drawn at two drawing temperatures, around PHB's T(g) (2 degrees C) for PHB-rich blends and around PLLA's T(g) (60 degrees C) for PLLA-rich blends. Differential scanning calorimetry analysis showed that this system was immiscible over the entire composition range. Mechanical properties of all of the samples were improved in proportion to the draw ratio. Although PLLA domains in bacterial-PHB-rich blends remained almost unstretched during cold drawing, a good interfacial adhesion between two polymers and the reinforcing role of PLLA components led to enhanced mechanical properties proportionally to the PLLA content at the same draw ratio. On the contrary, in the case of UHMW-PHB-rich blends, the minor component PLLA was found to be also oriented by cold drawing in ice water due to an increase in the interfacial entanglements caused by the very long chain length of the matrix polymer. As a result, their mechanical properties were considerably improved with increasing PLLA content compared with the bacterial-PHB system. Scanning electron microscopy observations on the surface and cross-section revealed that a layered structure with uniformly oriented microporous in the interior was obtained by selectively removal of PLLA component after simple alkaline treatment.

Calorimetry, Differential Scanning↗
PubMed2005

Curcumin impregnation improves the mechanical properties and reduces the inflammatory response associated with poly(L-lactic acid) fiber.

We investigated poly(L-lactic acid) (PLLA) fibers and coils, simulating stents and the influence of impregnation with curcumin, a non-steroidal anti-inflammatory drug, intended to reduce the pro-inflammatory property of these implants. Fibers obtained by melt extrusion of 137 kDa PLLA resin containing 10% curcumin (C-PLLA) exhibited a stable curcumin release rate for periods up to 36 days. Curcumin increased the fiber tensile strength at break and decreased embrittlement vs. controls in 36 day 37 degrees C saline incubation. A mouse peritoneal phagocyte model was employed to test the anti-inflammatory properties of C-PLLA fibers in vitro. Myeloperoxidase and non-specific esterase activity assays were performed for adherent cells (polymorphonuclear leukocytes (PMN) and macrophages (MPhi), respectively). PMN and MPhi adhesion to C-PLLA fibers were significantly reduced compared to control PLLA fibers (2.6 +/- 0.91) x 10(5) vs. (5.6 +/- 0.67) x 10(5) PMN/cm2 and (3.9 +/- 0.23) x 10(3) vs. (9.1 +/- 0.7) x 10(3) MPhi/cm2 (P < 0.05), respectively. In addition, superoxide release in the phagocyte pool contacting C-PLLA fibers was 97% less than that for PLLA controls. A fresh human whole blood recirculation system was employed to analyze cell adhesion under flow conditions, employing scanning electron microscopy (SEM). Reduced adhesion of cells on C-PLLA fiber coils vs. controls was observed. These in vitro studies demonstrate that bulk curcumin impregnation can reduce the inflammatory response to bioresorbable PLLA fibers, whilst improving mechanical properties, thereby suggesting curcumin loading may benefit PLLA-based implants.

Animals↗
PubMed2001

Behavior of osteoblasts on a type I atelocollagen grafted ozone oxidized poly L-lactic acid membrane.

With oxidizing poly-L-lactic acid (PLLA) surface by ozone, peroxide groups are easily generated on the surface. Those peroxides are broken down by redox-coupling reaction, and provide active species that initiate grafting by reaction with the collagen molecules. The surface density of generated peroxide on a PLLA surface was determined by an iodide method. The maximum concentration of peroxide was about 2.87 x 10(-8) mol/cm2 when ozone oxidation was performed at 60 V for 60 min. After the surface oxidation, type I atelocollagen was grafted onto PLLA surface. All physical measurements on the collagen-grafted surface indicated that the PLLA surface was effectively grafted with type I atelocollagen. Behavior of rat calvaria osteoblasts on type I atelocollagen grafted PLLA (PLLA + COL) surface was observed. Initial attachment of osteoblasts on the surface was significantly enhanced, and it is assumed that the atelocollagen matrix supported the initial attachment and growth of cells. Collagenous protein synthesis of osteoblasts was maintained at relatively low level in the early stage of proliferation due to the primarily existing grafted type I atelocollagen, and then increased in 7 days as the osteoblast differentiated. After 7 days, collagenous protein synthesis in osteoblasts was activated. Alkaline phosphatase (ALPase) activity and mineralization by osteoblasts were promoted on PLLA + COL surface. In comparison with PLLA + COL, non-treated PLLA and tissue culture plate (TCPS) did not show any feature expressed in osteoblasts' maturation up to 9 days in this experiment. The grafted type I atelocollagen provided a favorable matrix for cell migration in relation with collagenase expression. Ozone oxidation might be a favorable method for surface modification of PLLA membranes by collagen grafting, and cell behavior could be modulated by the grafted collagen.

Animals↗
PubMed2000

Characterization and determination of origin of lactic acid bacteria from a sorghum-based fermented weaning food by analysis of soluble proteins and amplified fragment length polymorphism fingerprinting.

The group that includes the lactic acid bacteria is one of the most diverse groups of bacteria known, and these organisms have been characterized extensively by using different techniques. In this study, 180 lactic acid bacterial strains isolated from sorghum powder (44 strains) and from corresponding fermented (93 strains) and cooked fermented (43 strains) porridge samples that were prepared in 15 households were characterized by using biochemical and physiological methods, as well as by analyzing the electrophoretic profiles of total soluble proteins. A total of 58 of the 180 strains were Lactobacillus plantarum strains, 47 were Leuconostoc mesenteroides strains, 25 were Lactobacillus sake-Lactobacillus curvatus strains, 17 were Pediococcus pentosaceus strains, 13 were Pediococcus acidilactici strains, and 7 were Lactococcus lactis strains. L. plantarum and L. mesenteroides strains were the dominant strains during the fermentation process and were recovered from 87 and 73% of the households, respectively. The potential origins of these groups of lactic acid bacteria were assessed by amplified fragment length polymorphism fingerprint analysis.

Bacterial Proteins↗
PubMed1997

Ingredient selection for plastic composite supports for L-(+)-lactic acid biofilm fermentation by Lactobacillus casei subsp. rhamnosus.

Plastic composite supports containing 50% agricultural products (oat hulls, soybean hulls, yeast extract, soybean flour, dried bovine erythrocytes, bovine albumin, and/or mineral salts) and 50% (wt/wt) polypropylene were produced by high-temperature twin-screw extrusion. The research employed two half sets of a five-factorial fractional design (2(5 - 1)) to evaluate the effects of different agricultural components on the properties of the plastic composite supports and to select the best plastic composite support formulation for lactic acid fermentation. The biofilm population was affected by the contact angle and relative hydrophobicity of the supports (r = 0.79 to 0.82). Lactic acid was produced by the suspended cells (r = 0.96) and the biofilm on the plastic composite support discs (r = 0.85). Incorporation of yeast extract into plastic composite supports enhanced growth of free and attached cells in minimal medium (P < 0.0001). The presence of soybean hulls, yeast extract, or mineral salts in plastic composite supports produced less hydrophobic supports (P < 0.0001) and enhanced cell attachment (P < 0.03). Under all conditions, suspended-cell and polypropylene disc controls gave negligible lactic acid production and cell density. Plastic composite supports containing soybean hulls, yeast extract, soybean flour, bovine albumin, and mineral salts gave the highest biofilm population (2.3 x 10(9) CFU/g of support), cell density (absorbance of 1.8 at 620 nm), and lactic acid concentration (7.6 g/liter) in minimal medium.

Animals↗
PubMed2006

Lactic acid, pyruvic acid and lactate/pyruvate ratio in the Anoplocephalid tapeworm Stilesia globipunctata infecting sheep (Ovis aries).

Lactic acid content was found to vary among the different proglottid types of the parasite. This higher amount of lactic acid might be considered as the end product of anaerobic metabolism. The pyruvic acid level of the parasitic proglottides remained lower than lactate level. The intermediary carbohydrate metabolites, viz. lactate, pyruvate and the lactate/pyruvate ratio being indicators of high rate metabolism, their levels may notably infer the metabolic status of the parasite and also the interaction between the parasite species Stilesia globipunctata and the sheep host.

Anaerobiosis↗
PubMed2001

Lactic acid bacterial diversity in the traditional mexican fermented dough pozol as determined by 16S rDNA sequence analysis.

The lactic acid bacteria diversity of pozol, a Mexican fermented maize dough, was studied using a total DNA extraction and purification procedure and PCR amplification of 16S rDNA for gram-positive and related bacterial groups. Thirty-six clones were obtained and sequenced to 650 nucleotides. These partial sequences were identified by submission to the non-redundant nucleotide database of NCBI. The identified sequences were aligned with reference sequences of the closest related organisms. This analysis indicated that only 14 sequences were unique clones and these were identified as Lactococcus lactis, Streptococcus suis, Lactobacillus plantarum, Lact. casei, Lact. alimentarium, and Lact. delbruekii and Clostridium sp. Two non-ribosomal sequences were also detected. Unlike other environments analyzed with this molecular approach where many unidentified microorganisms are found, the identity of most sequences could be established as lactic acid bacteria, indicating that this is the main group among the gram-positive bacteria in pozol. Use of this molecular method permitted detection of lactic acid bacteria different from those previously isolated and identified by culture techniques

Clostridium↗
PubMed1967

Occurrence of an inhibitor of lactic Acid bacteria in green olives.

Green olives were found to contain an inhibitor(s) of several species of lactic acid bacteria usually associated with the Spanish-type brined olive fermentation. The inhibitor was demonstrated by the presence of inhibition zones surrounding tissue which had been cut from frozen olives and implanted in a seeded nutritive agar medium. Relative potencies of aqueous extracts of frozen olives were determined by a paper disc assay method. The Mission variety of olive contained the most inhibitor, and the Manzanillo and Ascolano, about 50 and 40% as much as the Mission variety, respectively. Sevillano and Barouni varieties contained comparatively little inhibitor. Effects of the inhibitor on growth rates of lactic acid bacteria were determined by adding various amounts of a concentrated aqueous extract of olives to a nutritive broth medium contained in screw-capped tubes. Of the four species of lactic acid bacteria tested, Leuconostoc mesenteroides was the most sensitive, and Lactobacillus plantarum was the least sensitive; Pediococcus cerevisiae and Lactobacillus brevis were intermediate in sensitivity. Extracts possessed a bactericidal property, as evidenced by their effect on L. mesenteroides. Sodium chloride, especially at concentrations of about 5% and higher, greatly increased the effectiveness of the inhibitor. The inhibitor was ethyl alcohol-soluble and was stable when heated at 100 C in aqueous solution. Potencies of extracts were reduced greatly by adjustment to pH 10, but no appreciable effect was noted by adjustment to pH 0.8.

Journal Article↗
PubMed1995

Kinetics of interactions of lactic acid, pH and atmosphere on the growth and survival of Yersinia enterocolitica IP 383 O:9 at 4 degrees C.

The influence of different lactic acid concentrations (0.1, 0.3, 0.5, 0.7, 0.9, 1.1% v/v), within pH range of 3.9 to 5.8 on the aerobic and anaerobic growth and survival kinetics of the virulent strain of Y. enterocolitica IP 383 O:9, was determined in Tryptone Soy Broth at 4 degrees C. Growth and survival data were analyzed and fitted by a modification of the Whiting and Cygnarowicz-Provost model, using the Minpack software library. Initial generation times, initial specific growth rates, lag times and death rates were subsequently calculated from the model parameters. The stability of the virulence plasmid in growing and surviving cells was examined using crystal violet binding, low-calcium response and congo red uptake. The results demonstrate the dependancy of the growth and survival kinetics on the interaction between the three variables. The effect of lactic acid on Y. enterocolitica is greater under anaerobic than aerobic conditions. Nevertheless, the organism was found to be more tolerant of low pH conditions under anaerobic atmosphere than under an aerobic atmosphere in the absence of lactic acid. The interaction between the variables did not lead to loss of the virulence plasmid in growing or non-growing cells.

Aerobiosis↗
PubMed2004

Diversity of lactic acid bacteria isolated from AOC Salers cheese.

The objective of this work was to describe the diversity of lactic acid bacteria in traditional raw milk Salers cheeses at the species and strain levels. The characterization of 381 strains isolated during ripening and various strain collections was investigated using physiological analysis and molecular techniques: Rep-PCR, species and genus specific amplifications and the sequence analysis of 16S rDNA for strain typing and taxonomic identification. The strains belonged to Lactobacillus plantarum, Lactobacillus paracasei, Lactococcus lactis, Lactococcus garviae, Enterococcus faecalis, Enterococcus faecium, Leuconostoc mesenteroides, Leuconostoc pseudomesenteroides, Streptococcus salivarius, Streptococcus millieri, Streptococcus macedonicus and Pediococcus pentosaceus. A wide phenotypic and genomic heterogeneity was observed within the different species (Lactobacillus plantarum, Lactobacillus paracasei and Leuconostoc mesenteroides) according to the origin and the time of ripening. The natural microflora was different from strain collection and each method must be combined to identify and characterize natural microflora. This study revealed the low selectivity of selective media used for the isolation of different groups of lactic acid bacteria except the Facultatively Heterofermentative lactobacilli medium selecting mesophile lactobacilli and SB medium selective for Enterococcus. The study reveals, for the first time, the microbial lactic acid bacteria community of Salers cheese and its diversity. A better knowledge of microbial flora will be useful to improve understanding of sensory quality of cheeses.

Cheese↗
PubMed1980

Inhibition of the adipose conversion of BALB/c 3T3 cells by 12-O-tetradecanoylphorbol-13-acetate: dependence on pH reduction via lactic acid production.

The effect of modifying culture pH on the adipose conversion of BALB/c 3T3 cells was studied. We have previously shown that the tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA) stimulates cellular lactic acid production, lowers the pH of the culture medium, and inhibits differentiation in this system. We now report that addition or organic acids such as D- or L-lactic acid or acetic acid to the culture medium mimicked the effect of TPA by lowering pH, stimulating cellular lactic acid production, and inhibiting the adipose conversion. Lowering the pH by changing the NaHCO3 concentration also inhibited differentiation. A comparison of Dulbecco's modified minimal essential medium (DMEM) vs minimal essential medium (MEM) indicated that in the former media, the rate and extent of differentiation was greater than in the MEM, and TPA neither inhibited differentiation nor stimulated lactate production. Our standard MEM medium could be made similar to DMEM with respect to the cells' response to TPA simply by raising the NaHCO3 concentration, hence, the buffering capacity, of MEM to that present in DMEM, suggesting that TPA can only inhibit differentiation in this system if it can lower culture pH via lactate production.

Adipose Tissue↗
PubMed2006

Poly(D,L-lactic acid)-block-(ligand-tethered poly(ethylene glycol)) copolymers as surface additives for promoting chondrocyte attachment and growth.

The poly(D,L-lactic acid)-block-(ligand-tethered poly(ethylene glycol)) copolymer was explored to engineer poly(D,L-lactic acid) (PLA) material to promote chondrocyte attachment and growth. The poly(D,L-lactic acid)-block-poly(ethylene glycol) copolymer (PLE) was synthesized by a coupling reaction between PLA and poly(ethylene glycol) (PEG) (M(n) 1000, 2000, and 4000 respectively), with the use of 4,4'-methylenediphenyl diisocyanate (MDI). Then the PLE was activated by methyl sulfonyl chloride and the amino acids or arginine-glycine-aspartic acid tripeptide (RGD) was attached, which was verified by the ninhydrin-UV method. The modified PLA films were simply prepared by blending PLA with PLE derivatives. ATR-FTIR, XPS, contact angle, and AFM results clearly showed that the PEG chain stably enriched on the surface of PLE-modified PLA films. The chondrocyte cytocompatibility test showed the modified PLA films could significantly improve chondrocyte attachment and proliferation.

Cell Adhesion↗
PubMed2006

Isolation and characterization of acid-tolerant, thermophilic bacteria for effective fermentation of biomass-derived sugars to lactic acid.

Biomass-derived sugars, such as glucose, xylose, and other minor sugars, can be readily fermented to fuel ethanol and commodity chemicals by the appropriate microbes. Due to the differences in the optimum conditions for the activity of the fungal cellulases that are required for depolymerization of cellulose to fermentable sugars and the growth and fermentation characteristics of the current industrial microbes, simultaneous saccharification and fermentation (SSF) of cellulose is envisioned at conditions that are not optimal for the fungal cellulase activity, leading to a higher-than-required cost of cellulase in SSF. We have isolated bacterial strains that grew and fermented both glucose and xylose, major components of cellulose and hemicellulose, respectively, to l(+)-lactic acid at 50 degrees C and pH 5.0, conditions that are also optimal for fungal cellulase activity. Xylose was metabolized by these new isolates through the pentose-phosphate pathway. As expected for the metabolism of xylose by the pentose-phosphate pathway, [(13)C]lactate accounted for more than 90% of the total (13)C-labeled products from [(13)C]xylose. Based on fatty acid profile and 16S rRNA sequence, these isolates cluster with Bacillus coagulans, although the B. coagulans type strain, ATCC 7050, failed to utilize xylose as a carbon source. These new B. coagulans isolates have the potential to reduce the cost of SSF by minimizing the amount of fungal cellulases, a significant cost component in the use of biomass as a renewable resource, for the production of fuels and chemicals.

Bacillus↗
PubMed1984

A numerical taxonomic study of lactic acid bacteria from vacuum-packed beef, pork, lamb and bacon.

A numerical taxonomic study using 79 unit characters has been performed on 100 isolates of lactic acid bacteria from refrigerated vacuum-packed beef, pork, lamb and bacon. Three clusters were observed at 78% S which contained all the strains apart from three unidentifiable streptobacteria, one Leuconostoc, and one strain of Pediococcus pentosaceus. One cluster (III) consisted of only one strain of Leuc. paramesenteroides and six unidentifiable Leuconostoc strains. The two largest clusters (I and II) were both composed entirely of streptobacteria. Cluster I contained 31 strains (G + C content 33.2-36.9 moles%) which were not identifiable with any described species. Cluster II contained 57 strains (G + C content 40.7-43.7 moles %) which were provisionally identified with Lactobacillus sake or Lact. bavaricus according to the lactic acid isomer produced. The division of nearly all the streptobacteria into two clearly defined clusters has resolved problems which have existed in the classification of lactic acid bacteria from vacuum-packed meat.

Animals↗