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Lactate eaters have an oral LD50 greater than 2000 mg/kg and the inhalation LC50 is generally above 5000 mg/m3 and they may be potential eye and skin irritants, but not skin sensitizers. No evidence of teratogenicity or maternal toxicity was observed in an inhalation (2-ethylhexyl-L-lactate) or dermal study (ethyl-L-lactate). Subacute inhalation studies have been conducted at concentration up to 600 mg/m3 or higher on four lactate esters (ethyl, n-butyl, isobutyl, and 2-ethylhexyl-L-lactate). Degenerative and regenerative changes in the nasal cavity were noted in all studies. The NOAEL in ethyl, n-butyl, and isobutyl-L-lactate vapor studies was 200 mg/m3. For aerosol exposure, 2-ethylhexyl-L-lactate, the most toxic of the lactates, minimal damage to the nasal epithelium was noted at 75 mg/m3 with vapor being slightly less toxic than the aerosol. Lactates do not appear to cause systemic toxicity, except at very high concentrations (1800 mg/m3 or higher). These systemic effects may be secondary to severe irritation seen at high doses. Sensory irritation tests suggest that a vapor exposure limit of 75 mg/m3 (~15 ppm) should prevent irritation in humans and therefore an occupational exposure level for vapor of 75 mg/m3 is recommended. However, aerosol exposure should be kept as low as possible. The low vapor pressure of the higher molecular weight esters would tend to keep vapor exposure low and the odor of lactate esters serves as a warning of exposure. These lactate eaters are readily biodegradable, suggesting little concern from an environmental point of view.

The aim of this study was lo determine the effects of 3 wk of daily rinsing with amine fluoride/stannous fluoride (AmF/SnF2) mouthrinse on plaque formation at buccal and interproximal sites, and on the acid production in plaque. in a randomized clinical trial with 30 participants. The amount of plaque was scored according to Turesky's modification of the Quigley and Hein index. Plaque samples were collected, before and after sucrose rinsing, from the buccal and interproximal surfaces of upper (pre)molars at two baseline visits and on days 2 and 7 after the discontinuation of 3 wk of daily rinsing. Metabolic acid ions were determined by capillary electrophoresis. The results at baseline showed higher lactic acid concentrations in resting interproximal plaque than in buccal plaque, and a higher acid production in response to sucrose challenge in buccal plaque than in interproximal plaque. After 3 wk of use of the AmF/SnF2 mouthrinse, no significant differences in plaque scores were observed, and the alleged reduction in acidogenicity of denial plaque was not significant on the second day after the last mouthrinse. We conclude that 3 wk of use of AmF/SnF2 rinse once daily does not result in a reduction of plaque formation or in a reduction of sucrose metabolism in buccal and interproximal plaque after discontinuing the rinse.

The pentose sugar L-arabinose is one of the most abundant components released by complete hydrolysis of non-starch polysaccharides of feed ingredients of vegetable origin. Two studies were conducted to investigate the apparent ileal digestibility and urinary excretion of L-arabinose at dietary inclusion levels of 50 and 100 g/kg, and 25, 50, 75 and 100 g/kg respectively, in pigs. As a reference, D-glucose was included in the studies. Water intake, ileal flow of volatile fatty acids and ileal and faecal digestibilities of dietary nutrients in pigs fed on the different diets were also examined. Castrated pigs were prepared with a post-valvular T-caecum cannula to measure ileal digestibility. Faecal digestibility was measured in non-cannulated pigs. Apparent ileal digestibility of L-arabinose was found to be approximately 70%. The presence of L-arabinose in the diet increased ileal flow of volatile fatty acids and lactic acid, suggesting the occurrence of microbial degradation of L-arabinose in the pig small intestine. L-arabinose was partly excreted in the urine. The extent of this urinary excretion as a percentage of intake increased linearly (P < 0.01) as the dietary level increased. In pigs fed on the 25 g L-arabinose/kg diet, 10.9% of the L-arabinose consumed appeared in the urine. This level was increased to 14.7% when pigs were fed on a diet containing 100 g L-arabinose/kg diet. Faecal digestibility and retention of nitrogen decreased significantly in pigs fed on the L-arabinose diets. Chemicals/CAS: arabinose, 147-81-9; lactic acid, 113-21-3, 50-21-5; nitrogen, 7727-37-9; Arabinose, 147-81-9; Fatty Acids, Volatile; Lactates; Lactic Acid, 50-21-5; Nitrogen, 7727-37-9

The ecotoxicity of lactic acid, its alkyl esters and selected metal salts was studied experimentally with the micro alga Selenastrum capricornutum, the crustacean Daphnia magna and the fish species Brachydanio rerio and Pimephales promelas. In addition, the biodegradation of lactate esters was also studied. The aim of the study was to provide predicted environmental data for additional alkyl homologues and metal salts. The ecotoxicity data are evaluated by means of Structure Activity Relations (SAR), using literature data on a non-polar narcotic mechanism of toxicity as a baseline for comparison. Lactate salts were evaluated by comparison to the toxicity of the metal ion. For the fish and D. magna, it was evident that methyl, ethyl, propyl and to a lesser extent butyl lactate were slightly more toxic in comparison to baseline non-polar narcotic toxicity data. The toxicity tests carried out with lactate-salts demonstrated clearly that the toxicity in standard tests is only determined by the associated cation and not by the lactate part. Lactic acid and its alkyl esters were degraded for more than 60% in the ready biodegradability tests and from the data presented, it is evident that the majority of alkyl lactates are readily biodegradable. The results presented in this study indicate that alkyl lactate esters show some differences in their ecotoxicity when compared to non-polar narcotic compounds in but that these differences are generally small. When aquatic toxicity is considered together with their rapid tendency to biodegrade, it is concluded that lactate esters show generally favourable environmental characteristics. Chemicals/CAS: Esters; Lactates; Lactic Acid, 50-21-5

The organic acid lactate is the predominant fermentation product of Lactobacillus plantarum. The undissociated form of this organic acid is a strong growth inhibitor for the organism. Different theories have been postulated to explain the inhibitory effects of lactic acid: (i) toxicity arising from the dissipation of the membrane potential, (ii) acidification of the cytosol, or (iii) intracellular anion accumulation. In general, organic acid stresses are complex to study, since their toxicity is highly dependent on their degree of dissociation and thus on the pH. In this study, transcription profiles of L. plantarum grown in steady-state cultures that varied in lactate/lactic acid concentration, pH, osmolarity and absolute and relative growth rate, were compared by microarray analysis. By doing so, the differential expression of multiple groups of genes could specifically be attributed to the different aspects of lactic acid stress. A highly coherent group of lactic acid- responsive, cell surface protein-encoding genes was identified, to which no function has previously been assigned. Moreover, a group of genes that showed increased expression in response to the combination of lactic acid and a lower growth rate is expected to be involved in the formation of the alternative fermentation end-products malate, acetate and ethanol. One of these pathways is the phosphoketolase by-pass that is typical for bifidobacteria. © 2005 SGM.

The benefits of using lactic acid bacteria in the food chain, both through direct consumption and production of ingredients, are increasingly recognised by the food industry and consumers alike. The regulatory environment surrounding these products is diverse, covering foods and food ingredients, processing aids, feed additives and dietary supplements. On a global basis, there are different approaches taken by the various regulatory authorities. While in Europe, the national legislation is gradually being harmonised, predominantly through the Novel Foods Regulation, there is still a wide disparity between the stringency of regulation of microbial products fed to animals and the comparatively relaxed approach to 'non-novel' microbial products intended for human consumption. In the United States, the onus is on self-regulation of the manufacturer, with the Generally Recognised As Safe (GRAS) and Dietary Supplement Health Education Act (DSHEA) notification schemes encouraging industry to be more open about the ingredients they market. In Japan, the Foods for Special Health Use system continues to gain recognition as more products are approved, and is a potential model for other countries in regulating functional foods. Despite the different approaches to regulating these products, safety of microorganisms such as lactic acid bacteria in the food chain is paramount in all countries. This paper discusses the regulatory requirements of microbial products, predominantly lactic acid bacteria within the global markets, focusing mainly on the developments in Europe.

The shelf-life of fresh-cut lettuce packed in a modified atmosphere (MA) is determined by its "overall visual quality" (OVQ), being a measure of its general appearance based on colour and shape criteria. In addition to the OVQ, the development of off-flavour and acid off-smell reduces consumer acceptance of such products. Concomitant with these changes in organoleptic properties, there is a rapidly developing microbial population inside the MA package (MAP), dominated by lactic acid bacteria. We studied the bacterial population dynamics of active MAP freshcut lettuce as well as the effect of metabolites produced by the bacteria (lactic acid and acetic acid) on lettuce quality aspects. Within 3 days of packaging, the oxygen concentration in the package was reduced to near zero, and this resulted in the selective advantage of lactic acid bacteria, in particular Leuconostoc and Lactococcus species. Leuconostoc, when cultivated on lettuce-enriched artificial medium, was found to produce both acetic and lactic acids. Low concentrations of acetic and lactic acids were found in MAP lettuce after 5 days of storage at 7°C. Freshly prepared fresh-cut product treated with comparably small amounts of acetic and lactic acids showed severe quality loss. This was reflected by rapid browning, yellowing and loss of texture. The experiments demonstrate that, under anaerobic conditions, organic acids are produced by lactic acid bacteria, affecting both off-flavour production and sensorial quality in fresh-cut lettuce. © 2016, International Society for Horticultural Science. All rights reserved.

The degradation of lactic acid under anoxic conditions was studied in several strains of Lactobacillus buchneri and in close relatives such as Lactobacillus parabuchneri, Lactobacillus kefir, and Lactobacillus hilgardii. Of these lactobacilli, L. buchneri and L. parabuchneri were able to degrade lactic acid under anoxic conditions, without requiring an external electron acceptor. Each mole of lactic acid was converted into approximately 0.5 mol of acetic acid, 0.5 mol of 1,2-propanediol, and traces of ethanol. Based on stoichiometry studies and the high levels of NAD-linked 1,2-propanediol-dependent oxidoreductase (530 to 790 nmol min-1 mg of protein-1), a novel pathway for anaerobic lactic acid degradation is proposed. The anaerobic degradation of lactic acid by L. buchneri does not support cell growth and is pH dependent. Acidic conditions are needed to induce the lactic-acid-degrading capacity of the cells and to maintain the lactic-acid-degrading activity. At a pH above 5.8 hardly any lactic acid degradation was observed. The exact function of anaerobic lactic acid degradation by L. buchneri is not certain, but some results indicate that it plays a role in maintaining cell viability. Chemicals/CAS: acetic acid, 127-08-2, 127-09-3, 64-19-7, 71-50-1; alcohol, 64-17-5; lactic acid, 113-21-3, 50-21-5; nicotinamide adenine dinucleotide, 53-84-9; oxidoreductase, 9035-73-8, 9035-82-9, 9037-80-3, 9055-15-6; propylene glycol, 57-55-6; Acetic Acid, 64-19-7; Culture Media; Lactic Acid, 50-21-5; NADH Dehydrogenase, EC 1.6.99.3; Propylene Glycol, 57-55-6

Most fermentation products have a feedback inhibiting effect on the host organism. In situ product recovery (ISPR) can be a means to overcome this product inhibition in fermentations. Particles such as solvent impregnated resins or capsules can be valuable tools for product recovery based on extraction. To evaluate, which kind of particle will be feasible for a certain kind of fermentation product an evaluation is presented here. Furthermore, an assessment is made what the impact is of ISPR for enhancing productivities in relatively non-inhibiting (lactic acid), fairly inhibiting (phenol) and severely inhibiting (erythromycin) fermentation products. A process containing solvent impregnated resins or capsules is evaluated based on enhanced productivities and cost-effectiveness. It is shown that applying these particles inside a fermentor can result in a decrease in ±30% of total manufacturing costs for pharma-intermediate production.

On the basis of the comparison of the nucleotide sequences of the histidine decarboxylase genes (hdcA) of Lactobacillus 30A and Clostridium perfringens and the amino acid sequences of these histidine decarboxylases and those of Lactobacillus buchneri and Micrococcus, oligonucleotides unique to the hdcA genes were synthesized and used in PCR. All histidine-decarboxylating lactic acid bacteria gave a signal with primer set JV16HC/JV17HC in PCR. In addition to this primer set, CL1/CL2 and CL1/JV17HC were also useful for the detection of histamine-forming Leuconostoc oenos strains in PCR. The 150 base pair amplification product of the decarboxylating Leuc. oenos strain generated with primer set CL1/CL2 was sequenced. Alignment studies showed a high degree of relatedness among the hdcA gene products of Gram-positive bacteria. The amplification products of the hdcA genes from Lact. buchneri and Leuc. oenos were used to serve as a DNA probe in hybridization studies. All histidine-decarboxylating lactic acid bacteria gave a hybridization signal with the DNA probes. In hybridization only one false-positive signal with a Lactobacillus lindneri strain was observed, which was anticipated to contain a truncated hdcA gene. In addition to these DNA probe tests, a simple and reliable activity test is presented, which can be used during starter selection to test strains for histidine decarboxylase activity.

Lactic acid bacteria (LAB) employ sucrase-type enzymes to convert sucrose into homopolysaccharides consisting of either glucosyl units (glucans) or fructosyl units (fructans). The enzymes involved are labeled glucansucrases (GS) and fructansucrases (FS), respectively. The available molecular, biochemical, and structural information on sucrase genes and enzymes from various LAB and their fructan and a-glucan products is reviewed. The GS and FS enzymes are both glycoside hydrolase enzymes that act on the same substrate (sucrose) and catalyze (retaining) transglycosylation reactions that result in polysacchande formation, but they possess completely different protein structures. GS enzymes (family GH70) are large multidomain proteins that occur exclusively in LAB. Their catalytic domain displays clear secondary-structure similarity with α-amylase enzymes (family GH13), with a predicted permuted (β/α)8 barrel structure for which detailed structural and mechanistic information is available. Emphasis now is on identification of residues and regions important for GS enzyme activity and product specificity (synthesis of α-glucans differing in glycosidic linkage type, degree and type of branching, glucan molecular mass, and solubility). FS enzymes (family GH68) occur in both gram-negative and gram-positive bacteria and synthesize β-fructan polymers with either β-(2→6) (inulin) or β-(2→1) (levan) glycosidic bonds. Recently, the first high-resolution three-dimensional structures have become available for FS (levansucrase) proteins, revealing a rare five-bladed β-propeller structure with a deep, negatively charged central pocket. Although these structures have provided detailed mechanistic insights, the structural features in FS enzymes dictating the synthesis of either β-(2→6) or β-(2→1) linkages, degree and type of branching, and fructan molecular mass remain to be identified. Copyright © 2006, American Society for Microbiology. All Rights Reserved.

The hypothesis was studied that intestinal microbial metabolites play a role in the pathogenesis of inflammatory bowel disease. For that purpose, an in vitro model of the colon was inoculated with fresh feces of six healthy individuals and eight inflammatory bowel disease patients. Samples were taken from the model over time to analyze metabolites from both saccharolytic and proteolytic fermentation. Microbiotas from inflammatory bowel disease patients produced significantly more short-chain fatty acids and ammonia than microbiotas from healthy individuals. Furthermore, the branched-chain fatty acid production was 25% higher after inoculation with microbiotas from patients than after inoculation with microbiotas from healthy individuals. Phenolic compounds were produced by all microbiotas, with large interindividual variation. The production of (potentially toxic) metabolites may play a role in the onset or chronicity of inflammatory bowel disease, because they were produced in higher amounts by microbiotas from these patients than by microbiotas from healthy individuals.

Non-axenic operation of a 400 L trickle bed reactor inoculated with the thermophile Caldicellulosiruptor saccharolyticus, yielded 2.8 molH 2mol hexose converted. The reactor was fed with a complex medium with sucrose as the main substrate, continuously flushed with nitrogen gas, and operated at 73°C. The volumetric productivity was 22 mmolH2(L filterbed h). Acetic acid and lactic acid were the main by-products in the liquid phase. Production of lactic acid occurred when hydrogen partial pressure was elevated above 2% and during suboptimal fermentation conditions that also resulted in the presence of monoand disaccharides in the effluent. Methane production was negligible. The microbial community was analyzed at two different time points during operation. Initially, other species related to members of the genera Thermoanaerobacterium and Caldicellulosiruptor were present in the reactor. However, these were out-competed by C. saccharolyticus during a period when sucrose was completely used and no saccharides were discharged with the effluent. In general, the use of pure cultures in non-sterile industrial applications is known to be less useful because of contamination. However, our results show that the applied fermentation conditions resulted in a culture of a single dominant organism with excellent hydrogen production characteristics. © 2008 Wiley Periodicals, Inc.

Organo psycho syndrome (OPS) or chronic toxic encephalopathy (CTE) is a neurotoxic condition reported following long-term exposure to paints containing organic solvent and to other solvents. Lactate esters are finding wider use as solvents. Lactate esters have been well studied in standard toxicity tests, but specific neurotoxicity studies have not been conducted. No clinical signs of chronic neurotoxicity have been observed in standard toxicity tests. Lactate esters are rapidly hydrolyzed in the body to lactic acid and the corresponding alcohol. Alcohols have been reported to have acute neurotoxic effects, usually following high levels of ingestion. The literature on alcohols was reviewed to establish the no-observed-adverse-effect level (NOAEL) for acute neurotoxicity and to look for any evidence of chronic neurotoxicity from the alcohols produced by hydrolysis of the lactate esters. The NOAELs were compared with the potential amounts of alcohol produced by hydrolysis of different lactate esters at 200 mg/m3 (the NOAEL for most of the lactate esters). In all cases neither acute nor chronic neurotoxicity would be expected based on the amounts of alcohol produced by hydrolysis of the lactate esters at their NOAELs. L-Lactic acid is a normal metabolite in the body and is not considered neurotoxic. Based on this information there is no evidence to suggest that L-lactate esters can cause any chronic neurotoxicity, OPS, or CTE. © 2001 Academic Press.

The aim of this study was to investigate the effect of galacto-oligosaccharides, lactulose, apple fiber and sugar beet pectin on the composition and activity of human colonic microbiota of lean and obese healthy subjects using an in vitro model of the proximal colon: TIM-2. Substrate fermentation was assessed by measuring the production of short-chain and branched-chain fatty acids, lactate and ammonia and by studying the composition of the bacterial communities over time. The results suggest that energy harvest (in terms of metabolites) of lean and obese microbiotas is different and may depend on the fermentable substrate. For galactooligosaccharides and lactulose, the cumulative amount of short-chain fatty acids plus lactate produced in TIM-2 was lower in the fermentation experiments with the lean microbiota (123 and 155 mmol, respectively) compared to the obese (162 and 173 mmol, respectively). This was reversed for the pectin and the fiber. The absolute amount produced of short-chain fatty acids including lactate was higher after 72 h in the fermentation experiments with apple fiber-L (108 mmol) than with apple fiber-O (92 mmol). Sugar beet-L was also higher (130 mmol) compared to sugar beet-O (103 mmol). Galacto-oligosaccharides and lactulose boosted the balance of health-promoting over toxic metabolites produced by the microbiota from obese subjects. Firmicutes were more predominant in the inoculum prepared from feces of obese subjects compared to lean subjects. The average abundance at time zero was 92% and 74%, respectively. On the other hand, Bacteroidetes were more dominant in the microbiota prepared with homogenates from lean subjects with an average abundance of 22% compared with the microbiota prepared with homogenates from obese subjects (3.6%). This study brings evidence that different fermentable carbohydrates are fermented differently by lean and obese microbiotas, which contributes to the understanding of the role of diet and the microbiota in tackling obesity. Copyright:

Lactose maldigestion and intolerance affect a large part of the world population. The underlying factors of lactose intolerance are not fully understood. In this review, the role of colonic metabolism is discussed, i.e. fermentation of lactose by the colonic microbiota, colonic processing of the fermentation metabolites and how these processes would play a role in the pathophysiology of lactose intolerance. We suggest that the balance between the removal and production rate of osmotic-active components (lactose, and intermediate metabolites, e.g. lactate, succinate, etc.) in the colon is a key factor in the development of symptoms. The involvement of the colon may provide the basis for designing new targeted strategies for dietary and clinical management of lactose intolerance. © 2008 The Authors. Chemicals / CAS: lactic acid, 113-21-3, 50-21-5; lactose, 10039-26-6, 16984-38-6, 63-42-3, 64044-51-5; succinic acid, 110-15-6; Lactates; Lactose, 63-42-3

Microorganisms are generally sensitive to high concentrations of products that they excrete. Such product inhibition and toxicity effects can significantly be reduced by the integration of fermentations with separation technologies to remove the products continuously. Cost-calculations are required to select the preferred integration method. This paper presents a shortcut calculation method that provides easy interpretable results to assist the reader in making rational design choices. The method distinguishes four main cost categories, being capital and operational expenditure for both fermentation and product recovery. We have applied these cost correlations to the production of three typical bio-based bulk chemicals. The results show the origin of the most significant costs in the investigated integrated bio-processes. The presented method can be used to direct future research efforts and might assist in evaluating the impact of integrated product recovery techniques on total production costs of bio-chemicals. © 2010 Elsevier Ltd.

Recombinant lactobacilli are being developed which can be used as expression and delivery vectors of heterologous antigens in oral vaccination and other therapeutic applications. Because most Lactobacillus strains do not accept ligation mixtures, sufficiently pure plasmid DNA needs to be isolated from Lactobacillus casei to transform other Lactobacillus strains. The isolation of plasmid DNA from Gram-positive lactobacilli is complicated by the resilience of the peptidoglycan layer. Here a rapid, safe and efficient method is described that combines enzymatic breakdown of the cell wall and purification of the plasmid by commercially available DNA-binding columns. For the lysis-resistant L. casei strain, this method yields high levels of pure plasmid DNA that can be used for common molecular techniques, such as digestion and transformation, with high efficiency. Chemicals/CAS: Bacterial Proteins; Deoxyribonuclease BamHI, EC 3.1.21.-; Deoxyribonucleases, Type II Site-Specific, EC 3.1.21.4; DNA, Bacterial; endodeoxyribonuclease PvuI, EC 3.1.21.-; Immunodominant Epitopes

Objective: To determine the effect of consumption of milk fermented by Lactobacillus casei strain Shirota (L. casei Shirota) on the composition and metabolic activities of the intestinal microflora, and immune parameters in humans. Subjects: Twenty healthy male subjects aged 40-65 years were selected. Design: A placebo-controlled trial was performed in which 10 subjects were randomly assigned to a control and 10 to a treatment group. During the first and last two weeks of the 8-week study the subjects received a strictly controlled diet without fermented products. The same controlled diet was given during the intermediate 4-week test period but then the treatment group received three times daily 100 ml of fermented milk containing 109 CFU L. casei Shirota/ml, whereas the same amount of unfermented milk was given to the subjects in the control group. Results: In comparison to the control group, the consumption of L. casei Shirota-fermented milk resulted in an increase of the Lactobacillus count in the faeces in which the administered L. casei Shirota was predominant at the level of 107 CFU/g wet faeces. This was associated with a significant increase in Bifidobacterium counts (P < 0.05). Some shifts in the other bacterial species were found, such as a decreased number of Clostridium; however the differences were not statistically different between the treatment and the control groups. The β-glucuronidase and β-glucosidase activities per 1010 bacteria decreased significantly (P < 0.05) at the second week of the 4-week test period with the consumption of L. casei Shirota-fermented milk. Furthermore, the consumption of the fermented milk product resulted in a slight but significant increase in the moisture content of the faecal samples (P < 0.05). No treatment effects were observed for any of the immune parameters measured (including natural killer (NK) cell activity, phagocytosis and cytokine production). Conclusions: The results suggest that consumption of L. casei Shirota-fermented milk is able to modulate the composition and metabolic activity of the intestinal flora and indicate that L. casei Shirota-fermented milk does not influence the immune system of healthy immunocompetent males.