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PubMed2000

Influence of lactic acid on the solubilization of protein during corn steeping.

The role of lactic acid (LA) in corn wet-mill steeping is not well understood. Because LA is known to improve wet-milling starch yields and steepwater contains a large amount of proteinaceous material, one of the effects of LA in steeping may be to help break down the endosperm protein matrix. Protein solubilization was studied for four different steeping solutions containing LA, sulfur dioxide (SO(2)), a combination of LA and SO(2), or no added chemicals at temperatures between 44 and 60 degrees C with steep times of up to 48 h. The accumulation of proteinaceous material in steepwater with time was sigmoidal regardless of the steeping chemicals or temperature. The initial slow rate of solubilization appeared to be due to incomplete kernel hydration. Significantly greater amounts of protein were released in the presence of LA than in its absence, with the greatest amounts found when steeping was performed with both LA and SO(2). The increase of proteinaceous material in steepwater containing LA was not due to low pH, because steeping solutions containing other organic and inorganic acids did not increase steepwater protein. The effect of LA concentration was also studied. In the absence of SO(2), higher concentrations of LA resulted in higher steepwater protein concentrations. The opposite trend was observed in the presence of SO(2). Similar steepwater protein concentrations were obtained with DL-lactic acid and L-lactic acid, indicating that the additional protein release was not sensitive to isomeric effects.

Food Handling↗
PubMed1994

[Quantitative and qualitative determination of lactic acid in fecal filtrate in children].

The authors describe qualitative and quantitative methods for lactic acid assessment in children's feces. A total of 102 children with mainly lactose intolerance were examined. Benedict's test with feces filtrate, lactose tolerance test, and measurements of fecal carbohydrates were used in the diagnostic investigations. Mean lactic acid levels made up (mean +/- m) 33.3 +/- 3.6 mmol/l (6.3 +/- 1.0 in healthy infants on breast feeding and 6.0 +/- 1.3 mmol/l in those on mixed and formula feeding). Fecal carbohydrate levels were normal (below 5 g/l) in 12 infants, but lactic acid levels made up 67.8 +/- 6.1 mmol/l. Qualitative reaction to lactic acid in feces, starting from 44.4 mmol/l, was detected in 27% of infants. Differences in the values of healthy children and those with lactic carbohydrate intolerance were found significant (p < 0.001).

Child↗
PubMed1987

Cerebral lactic acid delivery and uptake during and after ischemia in the piglet.

To determine whether lactic acid is a cerebral substrate during and after partial ischemia in piglets, cerebral blood flow and arteriovenous differences of O2 and substrates were measured during control, after hemorrhagic hypotension, and 10 and 90 minutes after reperfusion with blood. During and following ischemia, alterations in cerebral O2 and glucose uptake indicated disturbed oxidative metabolism. Cerebral lactic acid uptake was similar at control, hypotension, and 90 minutes postreperfusion, but rose 10 minutes postreperfusion. Absent cerebral production of lactic acid during and net uptake following ischemia do not support lactic acid as a substrate since insufficient O2 was available for oxidation.

Animals↗
PubMed2002

Barley bread containing lactic acid improves glucose tolerance at a subsequent meal in healthy men and women.

In the present study, we evaluated whether a low glycemic index (GI) breakfast with lactic acid bread had an effect on glucose tolerance and insulinemia at a subsequent high GI lunch meal. A barley bread containing lactic acid and a reference barley bread were consumed in the morning after an overnight fast in random order by 10 healthy men and women. Four hours after the breakfasts, the subjects ate a standardized high GI lunch, and the blood glucose and insulin responses were measured for the next 3 h. Significant lowerings of the incremental glycemic area (-23%, P = 0.033) and of the glucose response at 95 min were found after the lunch meal when the barley bread with lactic acid was given as a breakfast. At 45 min after the lunch meal, the insulin level was significantly lower (-21%, P = 0.045) after the lactic acid bread breakfast, compared with the barley bread breakfast without lactic acid. We concluded that barley bread containing lactic acid eaten at breakfast has the potential to improve second-meal glucose tolerance at a high GI lunch meal 4 h later.

Adult↗
PubMed2003

L-Lactic acid production from raw cassava starch in a circulating loop bioreactor with cells immobilized in loofa (Luffa cylindrica).

L-Lactic acid was produced from raw cassava starch, by simultaneous enzyme production, starch saccharification and fermentation in a circulating loop bioreactor with Aspergillus awamori and Lactococcus lactis spp. lactis immobilized in loofa sponge. A. awamori was immobilized directly in cylindrical loofa sponge while the L. lactis was immobilized in a loofa sponge alginate gel cube. In the loofa sponge alginate gel cube, the sponge serves as skeletal support for the gel with the cells. The alginate gel formed a hard outer layer covering the soft porous gel inside. By controlling the rate and frequency of broth circulation between the riser and downcomer columns, the riser could be maintained under aerobic condition while the downcomer was under anaerobic condition. Repeated fed-batch L-lactic acid production was performed for more than 400 h and the average lactic acid yield and productivity from raw cassava starch were 0.76 g lactic acid g(-1) starch and 1.6 g lactic acid l(-1) h(-1), respectively.

Aspergillus↗
PubMed1977

Stability of lactic Acid bacteria to freezing as related to their Fatty Acid composition.

The viability of Streptococcus lactis and Lactobacillus sp. A-12 after freezing at -17 degrees C for 48 h was better preserved when the cells were grown in medium supplemented with oleic acid or Tween 80 (polyoxyethylene sorbitan monooleate). A pronounced change in the cellular fatty acid composition was noted when the bacteria were grown in the presence of Tween 80. In S. lactis the ratio of unsaturated to saturated fatty acids increased from 1.18 to 2.55 and in Lactobacillus sp. A-12 it increased from 0.85 to 1.67 when Tween 80 was added to the growth medium. The antibiotic cerulenin markedly inhibited the growth of lactic acid bacteria in tomato juice (TJ) medium but had almost no effect on the growth of the bacteria in TJ medium containing Tween 80 (or oleic acid). The antibiotic inhibited markedly the incorporation of [1-C]acetate but had no inhibitory effect on the incorporation of exogenous [1-C]oleate (or [1-C]palmitate) into the lipid fractions of lactic acid bacteria. Thus, the fatty acid composition of lactic acid bacteria, inhibited by the antibiotic cerulenin, can be modulated by exogenously added oleic acid (or Tween 80) without the concurrent endogenous fatty acid synthesis from acetate. The data obtained suggest that cerulenin inhibits neither cyclopropane fatty acid synthesis nor elongation of fatty acid acyl intermediates. The radioactivity of cells grown in the presence of [1-C]oleate and cerulenin was associated mainly with cyclopropane Delta19:0, 20:0 + 20:1, and 21:0 acids. As a consequence, cerulenin caused a decrease in the ratio of unsaturated to saturated fatty acids in lactic acid bacteria as compared with cells grown in TJ medium plus Tween 80 but without cerulenin. Cerulenin caused a decrease in the viability of S. lactis and Lactobacillus sp. A-12 after freezing at -17 degrees C for 48 h only when Tween 80 was present in the growth medium. We conclude that the sensitivity of lactic acid bacteria to damage from freezing can be correlated with specific alterations in the cellular fatty acids.

Journal Article↗
PubMed2006

Injectable poly-L-lactic acid (Sculptra): technical considerations in soft-tissue contouring.

BACKGROUND: Poly-L-lactic acid gained U.S. Food and Drug Administration approval for use in human immunodeficiency virus-related facial lipoatrophy in August of 2004. Since that time, it has become available for use in the United States for human immunodeficiency virus facial lipoatrophy patients and for off-label uses in other areas for soft-tissue contouring. This article is intended to enumerate reconstitution, injection techniques, management, and avoidance of complications. METHODS: The authors have pooled their experiences to arrive at a consensus opinion for recommendations on treatment protocols for injectable poly-L-lactic acid use. RESULTS: This article prescribes techniques to achieve safer, consistent results while minimizing risks of complications with injectable poly-L-lactic acid. Although the product has been used widely in Europe since 1999, physicians in the United States have only recently begun to explore the uses of Sculptra as a volumizing agent in the face and the body. U.S. physicians have benefited from the European experience with this product, including early problems secondary to overaggressive use, low-volume reconstitution, higher volume injection of product at one session, and inadequate time between injection sessions. CONCLUSIONS: The authors therefore have opted for a more conservative approach in their treatment recommendations. Higher volume dilution (8 to 12 cc), fewer vials used at each session, injections placed in the subcutaneous plane without any product being placed in the dermis, adequate time between injection sessions (at least 6 weeks), and postinjection patient massage should decrease the risks and avoid the potential complications associated with poly-L-lactic acid soft-tissue augmentation.

Adult↗
PubMed1995

Lactic acid inhibition of the growth of spoilage bacteria and cold tolerant pathogens on pork.

The antibacterial effects of a 3% solution of lactic acid at 55 degrees C were assessed, by examining aerobic bacterial growth on artificially-inoculated pork fat and lean tissue. Discs of fat or lean tissues, each of 10 cm2 surface area, were aseptically excised from pork Longissimus dorsi muscle and inoculated with the cold tolerant pathogens Listeria monocytogenes 4b Scott A no. 3, Yersinia enterocolitica 0:4,32 or Aeromonas hydrophila ATCC 7966, or with the wild type spoilage bacteria Pseudomonas fragi or Brochothrix thermosphacta. After inoculation, each meat disc was immersed in water or lactic acid for 15 s and aerobic bacterial growth followed during 15 days of storage at 4 degrees C. P. fragi and B. thermosphacta grew on both fat and lean, but the pathogens grew on fat tissue only and A. hydrophila did not survive on lean. Lactic acid reduced all test bacteria on fat to below detectable levels within 4 days of treatment and no bacteria could be recovered from acid-treated fat surfaces for the remainder of the 15-day storage interval. Bacteria attached to lean were generally more resistant to lactic acid. In some instances the acid was bacteriostatic (P. fragi, L. monocytogenes) while in others the population declined at a greatly reduced rate as compared with a similar population on fat (B. thermosphacta, Y. enterocolitica). A. hydrophila was equally sensitive to lactic acid on lean and fat. Depending upon the tested strain, tissue type and storage time, maximum reductions in the number of bacteria recovered from acid treated pork ranged from 1 to 8 log cycles. The high bactericidal efficacy of lactic acid applied to pork fat was attributable to a low tissue pH, which varied from 3.49 to 4.41 during the 15 days of aerobic storage.

Adipose Tissue↗
PubMed1992

Wound healing and wound contraction after palatal surgery and implantation of poly-(L-lactic) acid membranes in beagle dogs.

The effect of implantation of poly-(L-lactic) acid membranes on wound healing and wound contraction after palatal surgery was investigated macroscopically in beagle dogs. Thirty beagle dogs were randomly assigned to two experimental groups (group L and LM; both n = 12) and a control group (group C; n = 6). At 12 weeks of age, a soft-tissue defect was created in the median region of the palate by excising a standardized elliptical mucoperiosteal flap. This defect was closed according to the Von Langenbeck technique, leaving two areas of denuded bone. Immediately after surgery, poly-(L-lactic) acid membranes were implanted on the denuded bony areas in the animals of the LM group. In the L group, no poly-(L-lactic) acid membrane was used. Tattoo points were placed in the mucoperiosteum on opposite wound margins in all groups to quantify wound contraction. Standardized intraoral photographs were taken at regular intervals. Wound surface areas and weekly increments of the distance between the tattoo points were calculated. Clinical wound healing was significantly retarded in animals of the LM group. Wound contraction was comparable in both experimental groups and was restricted to the first 2 weeks after surgery. Corresponding lateral migration of the tattoo points in the median region of the palate in these groups occurred in the first week after surgery, followed by wound contraction in the second week. Implantation of poly-(L-lactic) acid membranes following palatal wounding in beagle dogs had no beneficial short-term effects on wound healing and contraction.

Analysis of Variance↗
PubMed1993

Fate of bioresorbable poly(lactic acid) microbeads implanted in artificial bone defects for cortical bone augmentation in dog mandible.

The fate was examined of poly(lactic acid) microbeads implanted in large artificial defects created in cortical bone of dog mandibles. Two poly(lactic acid) polymers--poly(L-lactic acid) (PLA 100) and poly(DL-lactic acid) (PLA 50)--were used to make microbeads by solvent evaporation with poly(vinyl alcohol) as surfactant. Histological observation of non-decalcified mandibular bone showed that no real bone regeneration existed in the experimental bone defects 18 months after PLA 100 microbeads implantation. The same observation was made 6 months after implantation of PLA 50 microbeads. PLA 100 and PLA 50 microbeads appeared unable to induce regeneration of cortical bone defects of dog mandible, in contrast to previous observations in man for PLA 50 large implants. The failure is tentatively assigned to the presence of poly(vinyl alcohol) at the surface of microbeads.

Animals↗
PubMed1999

Replacement of a metabolic pathway for large-scale production of lactic acid from engineered yeasts.

Interest in the production of L-(+)-lactic acid is presently growing in relation to its applications in the synthesis of biodegradable polymer materials. With the aim of obtaining efficient production and high productivity, we introduced the bovine L-lactate dehydrogenase gene (LDH) into a wild-type Kluyveromyces lactis yeast strain. The observed lactic acid production was not satisfactory due to the continued coproduction of ethanol. A further restructuring of the cellular metabolism was obtained by introducing the LDH gene into a K. lactis strain in which the unique pyruvate decarboxylase gene had been deleted. With this modified strain, in which lactic fermentation substituted completely for the pathway leading to the production of ethanol, we obtained concentrations, productivities, and yields of lactic acid as high as 109 g liter(-1), 0.91 g liter(-1) h(-1), and 1.19 mol per mole of glucose consumed, respectively. The organic acid was also produced at pH levels lower than those usual for bacterial processes.

Animals↗
PubMed1998

Foreign body gonitis caused by a broken poly-L-lactic acid screw.

Poly-L-lactic acid (PLLA), a biodegradable polymer, is generally considered to be gradually degraded without causing any severe tissue reaction. However, we encountered a patient who developed foreign body gonitis caused by screw breakage after fixation of an intercondylar prominence fracture with PLLA screws. This case suggests that care should be taken when PLLA materials are used to fix intraarticular fractures.

Adult↗
PubMed2005

Direct production of L+-lactic acid from starch and food wastes using Lactobacillus manihotivorans LMG18011.

This study describes several essential factors for direct and effective lactic acid production from food wastes by Lactobacillus manihotivorans LMG18011, and optimum conditions for simultaneous saccharification and fermentation using soluble starch and food wastes as substrates. The productivity was found to be affected by three factors: (1) initial pH, which influenced amylase production for saccharification of starch, (2) culture pH control which influenced selective production of L(+)-lactic acid, and (3) manganese concentration in medium which improved in production rate and yield of lactic acid. The optimum initial pH was 5.0-5.5, and the fermentation pH for the direct and effective fermentation from starchy substrate was 5.0 based on the yield of L(+)-lactic acid. Under these conditions, 19.5 g L(+)-lactic acid was produced from 200 g food wastes by L. manihotivorans LMG18011. Furthermore, the addition of manganese stimulated the direct fermentation significantly, and enabled complete bioconversion within 100 h.

Biodegradation, Environmental↗
PubMed1998

Conditions that promote production of lactic acid by Zymomonas mobilis in batch and continuous culture.

This study documents the similar pH-dependent shift in pyruvate metabolism exhibited by Zymomonas mobilis ATCC 29191 and ATCC 39676 in response to controlled changes in their steady-state growth environments. The usual high degree of ethanol selectivity associated with glucose fermentation by Z. mobilis is associated with conditions that promote rapid and robust growth, with about 95% of the substrate (5% w/v glucose) being converted to ethanol and C)2, and the remaining 5% being used for the synthesis of cell mass. Conditions that promote energetic uncoupling cause the conversion efficiency to increase to 98% as a result of the reduction in growth yield (cell mass production). Under conditions of glucose-limited growth in a chemostat, with the pH controlled at 6.0, the conversion efficiency was observed to decrease from 95% at a specific growth rate of 0.2/h to only 80% at 0.042/h. The decrease in ethanol yield was solely attributable to the pH-dependent shift in pyruvate metabolism, resulting in the production of lactic acid as a fermentation byproduct. At a dilution rate (D) of 0.042/h, decreasing from pH 6.0 to 5.5 resulted in a decrease in lactic acid from 10.8 to 7.5 g/L. Lactic acid synthesis depended on the presence of yeast extract (YE) or tryptone in the 5% (w/v) glucose-mineral salts medium. At D = 0.15/h, reduction in the level of YE from 3 to 1 g/L caused a threefold decrease in the steady-state concentration of lactic acid at pH 6. No lactic acid was produced with the same mineral salts medium, with ammonium chloride as the sole source of assimilable nitrogen. With the defined salts medium, the conversion efficiency was 98% of theoretical maximum. When chemostat cultures were used as seed for pH-stat batch fermentations, the amount of lactic acid produced correlated well with the activity of the chemostat culture; however, the mechanism of this prolonged induction effect is unknown. The levels of lactic acid produced by Z. mobilis in this study have not been previously reported. Zymomonas is Gram-negative, and at no time did microscopic inspection of lactic-acid-producing cultures indicate the presence of Gram-positive organisms. Although these observations are very preliminary in nature, they have implications for the regulation of glycolytic flux in Zymomonas, and demonstrate the possibility of an alternative fate for pyruvate previously presumed not to exits.

Carbon Dioxide↗
PubMed1992

Comparative acid tolerances and inhibitor sensitivities of isolated F-ATPases of oral lactic acid bacteria.

pH activity profiles and inhibitor sensitivities were compared for membrane ATPases isolated from three oral lactic acid bacteria, Lactobacillus casei ATCC 4646, Streptococcus mutans GS-5, and Streptococcus sanguis NCTC 10904, with, respectively, high, moderate, and low levels of acid tolerance. Membranes containing F1F0 ATPases were isolated by means of salt lysis of cells treated with muralytic enzymes. Membrane-free F1F0 complexes were then isolated from membranes by detergent extraction with Triton X-100 or octylglucoside. Finally, F1 complexes free of the proton-conducting F0 sector were obtained by washing membranes with buffers of low ionic strength. The pH activity profiles of the membrane-associated enzymes reflected the general acid tolerances of the organisms from which they were isolated; for example, pH optima were approximately 5.5, 6.0, and 7.0, respectively, for enzymes from L. casei, S. mutans, and S. sanguis. Roughly similar profiles were found for membrane-free F1F0 complexes, which were stabilized by phospholipids against loss of activity during storage. However, profiles for F1 enzymes were distinctly narrower, indicating that association with F0 and possibly other membrane components enhanced tolerance to both acid and alkaline media. All of the enzymes were found to have similar sensitivities to Al-F complexes, but only F1F0 enzymes were highly sensitive to dicyclohexylcarbodiimide. The procedures described for isolation of membrane-free F1F0 forms of the enzymes from oral lactic acid bacteria will be of use in future studies of the characteristics of the enzymes, especially in studies with liposomes.

Dental Plaque↗
PubMed2003

Rhizopus arrhizus--a producer for simultaneous saccharification and fermentation of starch waste materials to L(+)-lactic acid.

Rhizopus arrhizus, strain DAR 36017, produced L(+)-lactic acid in a simultaneous saccharification and fermentation process using starch waste effluents. Lactic acid at 19.5-44.3 g l(-1) with a yield of 0.85-0.96 g g(-1) was produced in 40 h using 20-60 g starch l(-1). Supplementation of nitrogen source may be unnecessary if potato or corn starch waste effluent was used as a production medium.

Agriculture↗
PubMed1994

Zinc phosphate cements: an evaluation of some factors influencing the lactic acid jet test erosion.

The lactic acid jet test was used to measure erosion rates of eight commercial zinc phosphate cements at 23 and 37 degrees C after 24 h and 2 months. Rates exceeded the ISO 9917 published limit of 0.1 mm/h when tested according to this specification (23 degrees C, 24 h), suggesting the limit should be increased. Erosion was measured by both weight loss and depth change. At 24 h erosion decreased as temperature increased, whereas after 2 months temperature had no significant effect. No trend was seen with increasing specimen maturity. Stannous fluoride may increase erosion resistance.

Hot Temperature↗
PubMed2005

Multidrug transporters in lactic acid bacteria.

Gram-positive lactic acid bacteria possess several Multi-Drug Resistance systems (MDRs) that excrete out of the cell a wide variety of mainly cationic lipophilic cytotoxic compounds as well as many clinically relevant antibiotics. These MDRs are either proton/drug antiporters belonging to the major facilitator superfamily of secondary transporters or ATP-dependent primary transporters belonging to the ATP-binding cassette superfamily of transport proteins. Here we summarize the existing data on these MDRs and discuss recent observations that suggest the use of new strategies in the ongoing battle against drug-resistant microbial pathogens.

ATP-Binding Cassette Transporters↗