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Four strains of lactic acid bacteria were investigated to determine if a relationship exists between accumulation of compatible solutes and the ability of cells to survive drying. Betaine was the major solute found in these lactic acid bacteria subjected to salt stress. Survival of cultures subjected to drying was considerably enhanced when this solute was accumulated by cells.
A customized stirred-tank biofilm reactor was designed for plastic-composite supports (PCS). In repeated-batch studies, the PCS-biofilm reactors outperformed the suspended-cell reactors by demonstrating higher lactic acid productivities (2.45 g l(-1) h(-1) vs 1.75 g l(-1) h(-1)) and greater glucose consumption rates (3.27 g l(-1) h(-1) vs 2.09 g l(-1) h(-1)). In the repeated fed-batch studies, reactors were spiked periodically with concentrated glucose (75%) to maintain a concentration of approximately 80 g of glucose l(-1) in the bioreactor. In suspended-cell fermentations with 10 g of yeast extract (YE) l(-1) and zero, one, two, and three glucose spikes, the lactic acid productivities were 2.64, 1.58, 0.80, and 0.62 g l(-1) h(-1), respectively. In comparison, biofilm reactors with 7 g of YE l(-1) and zero, one, two, and three glucose spikes achieved lactic acid productivities of 4.20, 2.78, 0.66, and 0.94 g l(-1) h(-1), respectively. The use of nystatin (30 U ml(-1)) subdued the contaminating yeast population with no effect on the lactic acid productivity of the biofilm reactors, but it did affect productivity in the suspended-cell bioreactor. Overall, in repeated fed-batch fermentations, the biofilm reactors consistently outperformed the suspended-cell bioreactors, required less YE, and produced up to 146 g of lactic acid l(-1) with 7 g of YE l(-1), whereas the suspended-cell reactor produced 132 g l(-1) with 10 g of YE l(-1).
The bacterial populations of the surface layer and the centre of 15 spoiled vacuum-packed cooked ring sausages were characterized. About 95% of the total bacterial population in the surface layer and 55% at the centre were lactic acid bacteria. Another large bacterial group at the centre consisted of Bacillus spp. The lactic acid bacteria on the surface and at the centre were quite similar. Atypical streptobacteria, i.e. homofermentative psychrotrophic lactobacilli, were a major group of lactic acid bacteria in the surface layer of the spoiled sausages. Three main homofermentative groups could be observed on the basis of different carbohydrate patterns. Heterofermentative lactic acid bacteria belonged mainly to genus Leuconostoc. The proportion of leuconostocs in the spoiled sausages was also quite large. They could be divided into three main groups on the basis of different carbohydrate fermentation patterns. The lactic acid bacteria population of spoiled cooked ring sausages thus seemed to be heterogeneous. The strains isolated resembled strains observed by other workers in meat and meat products.
Interactions among lactic acid starter and probiotic bacteria were investigated to establish adequate combinations of strains to manufacture probiotic dairy products. For this aim, a total of 48 strains of Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactococcus lactis, Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium spp. (eight of each) were used. The detection of bacterial interactions was carried out using the well-diffusion agar assay, and the interactions found were further characterized by growth kinetics. A variety of interactions was demonstrated. Lb. delbrueckii subsp. bulgaricus was found to be able to inhibit S. thermophilus strains. Among probiotic cultures, Lb. acidophilus was the sole species that was inhibited by the others (Lb. casei and Bifidobacterium). In general, probiotic bacteria proved to be more inhibitory towards lactic acid bacteria than vice versa since the latter did not exert any effect on the growth of the former, with some exceptions. The study of interactions by growth kinetics allowed the setting of four different kinds of behaviors between species of lactic acid starter and probiotic bacteria (stimulation, delay, complete inhibition of growth, and no effects among them). The possible interactions among the strains selected to manufacture a probiotic fermented dairy product should be taken into account when choosing the best combination/s to optimize their performance in the process and their survival in the products during cold storage.
Poly(lactic acid) microcapsules of pilocarpine hydrochloride were prepared and evaluated by measuring a miotic effect in rabbits. The microcapsule suspension showed prolongation of miosis and an improved bioavailability when compared with a standard eye dosage form.
Lactic acid bacteria are an important group of microorganisms, several of which are used in fermented food processes. Lactococcus lactis is a non-pathogenic, non-invasive and non-colonising gram-positive lactic acid bacterium, the genome sequence of which has been established. A great deal is known about the genetics, vectors, gene expression systems and protein secretion apparatus of this bacterium. Recently, recombinant strains of L. lactis have been developed that might provide in vivo delivery of cytokines and specific antigens across mucosal surfaces to the immune system of animals.
Nine yeast and four lactic acid bacterial strains, previously isolated from Zimbabwean traditionally fermented milk, were inoculated into ultra-high temperature treated (UHT) milk in both single and yeast-lactic acid bacteria co-culture. The lactic acid bacteria (LAB) strains consisted of Lactococcus lactis subsp. lactis biovar. diacetylactis C1, L. lactis subsp. lactis Lc39, L. lactis subsp. lactis Lc261 and Lactobacillus paracasei subsp. paracasei Lb11. The yeast strains used were Candida kefyr 23, C. lipolytica 57, C. lusitaniae 63, C. lusitaniae 68, C. tropicalis 78, Saccharomyces cerevisiae 71, S. dairenensis 32, C. colliculosa 41 and Dekkera bruxellensis 43. After 48-h fermentation at 25 degrees C, the samples were analysed for pH, viable yeast and bacterial counts, organic acids, volatile organic compounds (VOC) and carbon dioxide. The Lactococcus strains reduced the pH from about 6.6 to between 4.0 and 4.2, while Lb. paracasei subsp. paracasei Lb11 reduced the pH to about 5.4. Most of the yeasts, however, did not affect the final pH of the milk except for C. kefyr 23, which reduced the pH from 6.6 to 5.8. All the Lactococcus strains grew two log cycles during the 48-h fermentation period, while Lb. paracasei subsp. paracasei Lb11 grew about one log cycle. S. cerevisiae 71, C. colliculosa 41 and D. bruxellensis 43 showed poor growth in the milk in both single and co-culture. The other species of yeast grew about two log cycles. Candida colliculosa 41, S. dairenensis 32 and D. bruxellensis 43 showed reduced viability when in co-culture with Lb. paracasei subsp. paracasei Lb11. The samples in which C. kefyr 23 was used were distinct and characterised by large amounts of acetaldehyde, carbon dioxide and ethanol. However, in the samples where S. dairenensis, C. colliculosa, D. bruxellensis, C. lusitaniae, C. tropicalis, C. lipolytica and S. cerevisiae were used in co-culture, the final pH and metabolite content were mainly determined by the correspondin
The biodegradability of lactic acid based polymers was studied under controlled composting conditions (CEN prEN 14046), and the quality of the compost was evaluated. Poly(lactic acids), poly(ester-urethanes), and poly(ester-amide) were synthesized and the effects of different structure units were investigated. The ecotoxicological impact of compost samples was evaluated by biotests, i.e., by the Flash test, measuring the inhibition of light production of Vibrio fischeri, and by plant growth tests with cress, radish, and barley. All the polymers biodegraded to over 90% of the positive control in 6 months, which is the limit set by the CEN standard. Toxicity was detected in poly(ester-urethane) samples where chain linking of lactic acid oligomers had been carried out with 1,6-hexamethylene diisocyanate (HMDI). Both the Flash test and the plant growth tests indicated equal response to initial HMDI concentration in the polymer. All other polymers, including poly(ester-urethane) chain linked with 1,4-butane diisocyanate, showed no toxicological effect.
Molecular genetics of thermophilic lactic acid bacteria has advanced in several directions: exploitation of the milk proteins and sugars; primary and secondary metabolism; stress response; and molecular ecology of bacteria and their phages. These have singularly contributed to open new avenues of scientific interest in the field: comparative phage genomics; horizontal gene transfer events in bacterial or phage populations; and genetics of external polysaccharide production.
1. In anaesthetized and artificially ventilated dogs, a gracilis muscle was vascularly isolated and perfused at a constant flow rate of 11.9 +/- 2.2 ml min-1 100 g-1 (mean +/- S.E.M., n = 16; equivalent to 170.2 +/- 21.3% of its resting free flow). 2. Stimulation (3 Hz) of the obturator nerve produced twitch contractions of the gracilis muscle, reduced venous pH from 7.366 +/- 0.027 to 7.250 +/- 0.031 (n = 5), increased oxygen consumption from 0.62 +/- 0.24 to 2.76 +/- 0.46 ml min-1 100 g-1 (n = 5) and increased adenosine release from -0.40 +/- 0.14 (net uptake) to 1.36 +/- 0.50 nmol min-1 100 g-1 (n = 8). 3. Infusion of lactic acid (4.2 mM) into the artery reduced venous pH to 7.281 +/- 0.026 (n = 5) and increased adenosine release to 0.96 +/- 0.40 nmol min-1 100 g-1 (n = 8), but did not significantly alter oxygen consumption (0.80 +/- 0.19 ml min-1 100 g-1; n = 5). Stimulation (3 Hz) in the presence of lactic acid infusion produced no further significant changes in venous pH or adenosine release, but increased oxygen consumption to 2.53 +/- 0.37 ml min-1 100 g-1 (n = 5). 4. Infusion of a range of lactic acid concentrations (> or = 1.83 mM) produced dose-dependent increases in adenosine release. The maximum lactic acid concentration tested (5.95 mM) reduced venous pH to 7.249 +/- 0.023 (n = 5) and increased adenosine release to 2.64 +/- 1.26 nmol min-1 100 g-1 (n = 6). 5. A strong correlation existed between the adenosine release and the venous pH (r = -0.92); points obtained during muscle stimulation and/or lactic acid infusion fell on a single correlation line. 6. The vasoactivity of adenosine administered by close-arterial injection was unaltered by infusion of either lactic acid (7.2 mM) or saline. 7. These results suggest that the release of adenosine from skeletal muscle can be induced by a decrease in pH (probably at an intracellular site), and that this mechanism may contribute to the release of adenosine during muscle contractions.
A number of soft tissue filling agents are available in the U.S. and Europe. In Europe, poly-L-lactic acid was approved for soft tissue augmentation and correction of wrinkles in 1999. The clinical results from this synthetic implant may last up to two years. In this article, we report our experience using poly-L-lactic acid for correction of facial lipoatrophy and wrinkles in 300 patients since 1999. Poly-L-lactic acid is an ideal, resorbable filler material for soft tissue augmentation, especially in the lower one-half of the face. The aesthetic results are excellent and long-lasting. Clinical results and side effects are generally technique-dependent. The clinical results using poly-L-lactic acid for soft tissue augmentation are comparable to autologous fat grafting. However, surgical fat harvesting is not necessary, and treatment can be extended to elderly individuals and patients with infectious diseases who have little body fat.
The complexity of the coupled NADH oxidase-NADH peroxidase enzyme system in lactic acid bacteria makes it difficult to simultaneously determine the individual levels of both these enzymes spectrophotometrically. This study describes an improved assay to accurately determine low concentrations of NADH oxidase from enzyme suspensions containing NADH oxidase and NADH peroxidase. For the standardisation of the assay, pure NADH oxidase and NADH peroxidase were mixed in various proportions and the percentage recovery was estimated by both the currently available assay as well as by the improved assay reported in this study. The recovery of NADH oxidase using the currently available assay ranged from as low as -200% to as high as +102% as against 90-102% in the improved assay. The recovery percentage of NADH peroxidase ranged from 91% to 112% in both assays. The slopes of NADH oxidation by cell-free extracts of six lactic acid bacteria were also measured by both assays for the estimation of NADH oxidase and NADH peroxidase levels. The improved assay can further distinguish between NADH-H(2)O oxidase and NADH-H(2)O(2) oxidase and was successfully applied to identify the type of NADH oxidase in the lactic acid bacteria tested.
AIMS: The aim of the study was to characterize isolates of lactic acid bacteria from Beyaz cheese and to study some of their technologically important properties. METHODS AND RESULTS: Seventy-seven lactic acid bacteria isolated from Beyaz, a Turkish white-brined cheese made from raw ewes' milk without any starter, were classified by phenotypic criteria and sodium dodecyl sulphate-polyacrylamide gel electrophoresis of whole-cell proteins. Whole cells of Lactococcus lactis subsp. lactis and enterococci showed lipolytic and proteolytic activities. Strains were found that differed in terms of their acidifying and caseinolytic activity. Most of the enterococci isolates showed tyrosine decarboxylase activity; moreover, lactobacilli exhibited weak antibacterial activities against foodborne pathogens. CONCLUSIONS: Strains of lactic acid bacteria with interesting biotechnologically important properties may be found in Beyaz cheese. SIGNIFICANCE AND IMPACT OF THE STUDY: Lactic acid bacteria isolates with interesting biotechnological profiles may influence the quality and variety of dairy products, if they are used as starters, and their cheese-making characteristics seem promising.
Seven sportsmen, 100 meters and 400 meters runners are submitted to an effort test of 30 seconds. The subjects are on average 23.7 +/-2 years old. The purpose of our work is to study on the one hand the evlution of the anaerobic power. the heart rate and the lactic acid in blood during and after a bicycle test. and their relation, and on the other hand. to know the suitable pratical importance of the heart rate and the lactic acid in blood in connection with the intermittent efforts recovery aiming the anaerobic power developpement. These physiological parameters have been measured by a Monark bicycle 864, a sport-tester PE 3000 and a spectrophotometer JASCO 7800 UV/VIS. The power and the heart rate increase quickly in the 5 first seconds. Our subjects reach their average maximal anaerobic power at the 10th second, and then this power decreases progressively, while the heart rate continues to increase, without being maximal at the end of te test. Five minutes later it decreases in a half, while the lactic acid level calculated at the 30th second is continuing significantly. We have not found a significant relation between the measured parameters at the test stopping and during the recovery period (except between the lactic acid and the recovery index of the heart rate at the 25th minute). The lactic acid in blood would inform better about a good recovery during an interval training effort.
The separation of lactic acid from complex fermentation broth was examined. Liquid-liquid extraction using reversible chemical complexation for reactive extraction was chosen to be the separation method. Over 50% yield of lactic acid was obtained from fermented broth in a single extraction step, when using the tertiary amine as the extractant, 1-dekanol as the diluent and trimethylamine (TMA) as the stripping solution. The effect of complex media on the extraction behaviour has hardly been examined previously.
Sugar beet pulp and poly(lactic acid) (PLA) composites were prepared by compression-heating. The resultant thermoplastics had a lower density, but they had tensile strength similar to that of pure PLA specimens as well as the same geometric properties. Tensile properties depended on the initial water content of sugar beet pulp and the process by which composites were manufactured. In comparison with sugar beet pulp, the composite showed improved water resistance. This can be attributed to the hydrophobic character of PLA and pulp-matrix interactions. The composite thermoplastics showed suitable properties for potential use as lightweight construction materials.
The diversity of lactic acid bacteria occurring in the crop and intestinal content of ducks of different ages (5 to 34 days) was evaluated using the RAPD-PCR technique and comparative sequence analysis of 16S rRNA. Cluster analysis derived from isolates grown on Rogosa agar used for the enrichment of lactic acid bacteria, revealed at least twenty six different groups of organisms representing species, subspecies and strains belonging to Streptococcus, Enterococcus, Pediococcus, Weissella and Lactobacillus. Homofermentative and heterofermentative lactobacilli were identified, belonging to the phylogenetically defined Lb. acidophilus, Lb. salivarius and Lb. reuteri groups.
Five Acetobacter isolates from lactic acid fermented meat food for pets were characterized by 177 morphological, physiological and biochemical traits. Four isolates were identified as A. pasteurianus, one as A. aceti. It is emphasized that access of such bacteria to lactic acid fermented foods should be avoided.