Rate Of Lactic Acid Production Research Articles

Effects of high-fluoride dentifrice (5,000-ppm) on caries-related plaque and salivary variables

The aim of the present study was to measure the effects of a 5,000-ppm F toothpaste on caries-related factors in dental plaque and saliva. A 6-week clinical trial was designed with a total of 34 participants, of which 26 completed the study. The participants were assessed on four visits, 2 weeks apart. Sampling of approximal fluid for fluoride analysis and approximal plaque for organic acid analysis was performed. Chair-side tests were performed to register the lactic acid production rate on the tongue using Clinpro™ Cario L-Pop™, approximal plaque pH using the pH "strip method" and salivary buffer capacity and counts of cariogenic microorganisms using CRT Buffer(®) and CRT Bacteria(®). Six weeks' use of 5,000-ppm fluoridated (F) toothpaste significantly increased the approximal fluid F concentration (p < 0.05). There was a significant decrease in lactic acid production rate on the tongue assessed by Clinpro™ (p < 0.05). This was accompanied by changes in interproximal plaque acidogenicity, including significant reductions in AUC(5.7), AUC(6.2) and maximum pH fall and an increase in minimum pH (p < 0.05). A significant increase in the salivary buffer capacity and a reduction in the salivary mutans streptococci were observed (p < 0.05). The present study demonstrates the ability of 5,000-ppm F toothpaste to modify caries-related factors in dental plaque and saliva. The 5,000-ppm F toothpaste could be regarded as a possible effective regimen against caries in the near future.

Flow-type microbial chip for screening of a single bacterium

A microbial chip is demonstrated that immobilises microbes into micro holes using positive dielectrophoresis (DEP) for efficient screening. The DEP frequency was set at 10 MHz, which was found to be most effective to selectively immobilise live bacteria. The media including reactive agents can be flown into the chip continuously and therefore the reaction products can be continuously collected. Immobilisation of microbes enables quantification of the number of microbes involved in the reaction and makes their reactions conditions consistent. These advantages enable the proposed microbial chip to evaluate the production capacity of a single bacterium. To demonstrate it, the developed microbial chip was used to characterise microbes and evaluate biological activity. First, Corynebacterium bacterium was used as a sample bacteria. The chip successfully revealed the production capacity of lactic acid by a single C. bacterium. It was experimentally found that the production rate of lactic acid of Corynebacterium glutamicum increased 1.7 times and 3.8 times by adding pyruvic acid and sodium bicarbonate, respectively. Secondly, microbes belonging to the Corynebacterium group with respect to the lactic acid production were screened. Corynebacterium variabile was experimentally found to be the most productive among three tested members. The proposed microbial chip is readily applicable to an efficient microbial screening platform and potentially a reliable microbial sensor given the capacity of quantifying the total number of bacteria involved in the microbial reaction.

Evaluation of two bacteriocin-producing probiotic lactic acid bacteria as inoculants for controlling Listeria monocytogenes in grass and maize silages

This study evaluated the effectiveness as silage inoculants of two bacteriocin-producing lactic acid bacteria (LAB) with proven probiotic activity in post-weaned piglets, Lactococcus lactis CECT 539 and Pediococcus acidilactici NRRL B-5627, in combination with the ensiling strain Lactobacillus plantarum CECT 220. Four combinations of LAB were tested in grass and maize silages: L. plantarum (Lb), L. plantarum + L. lactis (LbL), L. plantarum + P. acidilactici (LbP), and the three species together (LbLP). Untreated silages and silages inoculated with commercial starters (L. plantarum + Lactobacillus buchneri + Enterococcus faecium) were prepared and used as controls. Since both bacteriocinogenic strains have shown antilisterial activity in vitro, this study also aimed to determinate their effectiveness for controlling Listeria monocytogenes in the silo. Therefore, silages were inoculated with the strain L. monocytogenes CECT 4032 (1.0×105cfu/g), the evolution of which was monitored throughout fermentation using microbiological and DNA based methods. Each treatment was assayed in triplicate in lab-scale silos and sampled after 1, 2, 8, 16 and 30 days to extract DNA and determination of the pH, volume, organic acids (lactic, acetic, propionic and butyric), alcohols (ethanol and propane-1, 2-diol), water soluble reducing sugars (WSRS) and make LAB and L. monocytogenes counts. Our results showed that the silages treated with bacteriocin-producing LAB had a higher rate of pH decline (P<0.01) and lactic acid production (P<0.01). After 30 days of fermentation, we observed low acetic acid (P<0.01) and ethanol (P<0.01), lower LAB counts (P<0.01) and higher (P<0.01) residual sugar concentrations in the Lb, LbL, LbP and LbLP silages. No L. monocytogenes colonies were found during ensilage; however, its DNA was present, which suggests that the adverse silage conditions (pH, anaerobiosis) might favour a viable but non-culturable state in the cells. In both forages, all treatments showed the anticipated disappearance of L. monocytogenes, unlike the control. It can be concluded that the bacteriocinogenic LAB tested in this study can be used as silage inoculants for controlling L. monocytogenes in the silo and also in the rumen of cattle due to their reported tolerance to acid.

Gamma irradiation of sorghum flour: Effects on microbial inactivation, amylase activity, fermentability, viscosity and starch granule structure

Malted and un-malted sorghum ( Sorghum bicolor (L.) Moench) flour was gamma irradiated with a dose of 10 kGy and then re-irradiated with 25 kGy. The effects of irradiation on microbial decontamination, amylase activity, fermentability (using an amylolytic L. plantarum MNC 21 strain), starch granule structure and viscosity were determined. Standard methods were used during determinations. The 10 kGy dose had no effect on microbial load of un-malted flour but reduced that of malted flour by 3 log cycles. Re-irradiation resulted in complete decontamination. Irradiation of malt caused a significant ( p<0.05) reduction in alpha and beta amylase activity (22% and 32%, respectively). Irradiation of un-malted flour increased the rates of utilization of glucose and maltose by 53% and 100%, respectively, during fermentation. However, microbial growth, rate of lactic acid production, final lactic acid concentration and pH were not affected. Starch granules appeared normal externally even after re-irradiation, however, granules ruptured and dissolved easily after hydration and gelatinization. Production of high dry matter density porridge (200 g dry matter/L) with a viscosity of 3500 cP was achieved by irradiation of un-malted flout at 10 kGy. Gamma irradiation can be used to decontaminate flours and could be utilized to produce weaning porridge from sorghum.

Effects of salt mixtures on Spanish green table olive fermentation performance

This work investigates the effect of sodium, potassium, and calcium chloride salts on the performance of Spanish green table olive fermentation using a simple centroid mixture design. The presence of calcium chloride hindered the diffusion of all sugars and delayed the period required to reach their respective maximum concentrations in brines. Such effects can prevent tumultuous processes and gas pocket spoilage. Acetic acid was present at low concentrations in all treatments but was not generated during fermentation. The production rate of lactic acid was either decreased or delayed by the presence of calcium chloride but adequate final conditions were always reached. The chemometric analysis classified treatments into groups according to the presence of calcium chloride and disclosed a stimulating effect of potassium on lactic acid production. Therefore, these techniques can be a useful tool to investigate olive fermentation performance. According to the results, acceptable Spanish green table olives can be produced using salt mixtures, with the subsequent reduced sodium content in the final products. The results obtained in this study could also be of interest for other fermented vegetables.

Effect of amino acid requirements on the growth and lactic acid production of Pediococcus acidilactici culture

The aim of this research was to investigate essential groups of amino acids and effect of amino acid supplementation. P. acidilactici culture was grown in chemically defined medium (CDM) with initial pH 6.35 and at 30°C. To minimize the number of experiments, the experimental design was based on grouping the metabolic amino acid pool. The selected amino acid groups were the following: a) phenylalanine and tyrosine; b) lysine, methionine, isoleucine; c) leucine and valine and d) histidine. The concentration of each selected amino acid in original CDM was 50 mg/l while its concentration in the modified CDM was reduced to 25 mg/l. Concentrations of biomass, lactic acid, glucose, and selected amino acids were measured. It was found that amount of Ile, Met, and Lys added in CDM-grown P. acidilactici was directly affected lactic acid production rate. Limitation of Phe, Tyr, Leu, Val, and His concentration added had the largest effect on cell growth and lactic acid production. The maximum specific growth rate (µmax) and the lactic acid production rate obtained from fermentation in modified CDM with 25 mg/l of Phe and Tyr (Run # A) and Leu and Val (Run # C), as compared with fermentation in original CDM, were improved by a factor of 3.4 and a factor of 2.7, respectively. The sub-optimal composition of amino acids in modified CDM was 25 mg/l of Phe, Tyr, Leu and Val at pH 5.5-5.8. Key words: Lactic acid bacteria, Pediococcus acidilactici, lactic acid, amino acid.

Kinetic analysis and mathematical modeling of growth and lactic acid production of Lactobacillus casei var. rhamnosus in milk whey

Lactobacillus casei is a lactic acid bacterium (LAB) that colonizes diverse ecological niches and that has found broad commercial application. The aim of this study was to characterize the kinetics of biomass production, lactic acid production, and substrate consumption of Lactobacillus casei var. rhamnosus cultured in deproteinized milk whey. Batch culture experiments were performed in an instrumented, 2-L, stirred tank bioreactor using different inoculum concentrations (0.5 to 1.0g/L) and lactose levels (35 to 70g/L). The time series of experimental data corresponding to biomass growth, lactose consumption, and lactic acid formation were differentiated to calculate the corresponding kinetic rates. Strong exponentially dependent product inhibition effects were evident at low lactic acid concentrations, and lactic acid production rate was partially associated with biomass growth. A mathematical model is presented that reproduces the experimental lactose, biomass, and lactic acid concentration profiles.

THE USE OF SELECTED LACTIC ACID BACTERIA STARTER CULTURES FOR IMPROVED THAI SAUSAGE FERMENTATION

ABSTRACT Improvement of the conventional sausage fermentation process was investigated by introducing six different external starter cultures including Pediococcus pentosaceous, Pediococcus acidilactici, Weissella cibaria, Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus sakei. The results of microbiological analysis indicated that the dominance of lactic acid bacteria could inhibit the growth of pathogens and spoilage. Sausages inoculated with starters exhibited lower pH (pH = 4.51–4.67) than the uninoculated control. The decrease of pH was attributed to organic acid, mainly by lactic acid production. The initial rate of lactic acid production in sausages inoculated with starter cultures was higher than the control. P. acidilactici showed the highest initial rate of lactic acid production (4.45 × 10−2 g/100g·h) and lactic acid yield (0.89), while the initial rate of lactic acid production and lactic acid yield were 2.66 × 10−2 g/100g·h and 0.63, respectively, in control experiments. The sausage inoculated with P. acidilactici recorded the highest scores for overall acceptability. PRACTICAL APPLICATIONS The fermentation of traditional fermented sausages is caused by natural, wild-type lactic acid bacteria such as lactobacilli and pediococci that originate from the row meat, or the process apparatus or the environment and takes 2–3 days at room temperature. The use of starter cultures in sausages production has improved food safety and to standardize product properties such as flavor compound, lactic acid, color and texture. In addition, the sensory of sausages inoculated with starter cultures are more acceptable than uninoculated sausages.

Improved oxygen transfer and increased l-lactic acid production by morphology control of Rhizopus oryzae in a static bed bioreactor

Rhizopus oryzae was immobilized on a cotton matrix in a static bed bioreactor. Compared with free cells in a stirred tank bioreactor, immobilized R. oryzae in this bioreactor gave higher lactic acid production but lower ethanol production. The highest lactic acid production rate (2.09 g/L h) with the final concentration of 37.83 g/L from 70 g/L glucose was achieved when operating the bioreactor at 700 rpm and 0.5 vvm air. To better understand the relationship between shear effects (agitation and aeration) and R. oryzae morphology and metabolism, oxygen transfer rate, fermentation kinetics, and lactate dehydrogenase activity were determined. In immobilized cell culture, higher oxygen transfer rate and lactic acid production were achieved but lower lactate dehydrogenase activity was found as compared with those in free cell culture operated at the same conditions. These results clearly imply that mass transport was the rate controlling step in lactic acid fermentation by R. oryzae.

Anaerobic homolactate fermentation withSaccharomyces cerevisiaeresults in depletion of ATP and impaired metabolic activity

Conversion of glucose to lactic acid is stoichiometrically equivalent to ethanol formation with respect to ATP formation from substrate-level phosphorylation, redox equivalents and product yield. However, anaerobic growth cannot be sustained in homolactate fermenting Saccharomyces cerevisiae. ATP-dependent export of the lactate anion and/or proton, resulting in net zero ATP formation, is suspected as the underlying cause. In an effort to understand the mechanisms behind the decreased lactic acid production rate in anaerobic homolactate cultures of S. cerevisiae, aerobic carbon-limited chemostats were performed and subjected to anaerobic perturbations in the presence of high glucose concentrations. Intracellular measurements of adenosine phosphates confirmed ATP depletion and decreased energy charge immediately upon anaerobicity. Unexpectedly, readily available sources of carbon and energy, trehalose and glycogen, were not activated in homolactate strains as they were in reference strains that produce ethanol. Finally, the anticipated increase in maximal velocity (V(max)) of glycolytic enzymes was not observed in homolactate fermentation suggesting the absence of protein synthesis that may be attributed to decreased energy availability. Essentially, anaerobic homolactate fermentation results in energy depletion, which, in turn, hinders protein synthesis, central carbon metabolism and subsequent energy generation.

Insulin Receptor Substrate-2 Regulates Aerobic Glycolysis in Mouse Mammary Tumor Cells via Glucose Transporter 1

The insulin receptor substrate (IRS) proteins are cytoplasmic adaptor molecules that function as signaling intermediates downstream of activated cell surface receptors. Based on data implicating IRS-2 but not IRS-1 in breast cancer invasion, survival, and metastasis, we assessed the contribution of IRS-1 and IRS-2 to aerobic glycolysis, which is known to impact tumor growth and progression. For this purpose, we used tumor cell lines derived from transgenic mice that express the polyoma virus middle T antigen (PyV-MT) in the mammary gland and that are wild-type (WT) or null for either Irs-1 (Irs-1-/-) or Irs-2 (Irs-2-/-). Aerobic glycolysis, as assessed by the rate of lactic acid production and glucose consumption, was diminished significantly in Irs-2-/- cells when compared with WT and Irs-1-/- cells. Expression of exogenous Irs-2 in Irs-2-/- cells restored the rate of glycolysis to that observed in WT cells. The transcription factor FoxO1 does not appear to be involved in Irs-2-mediated glycolysis. However, Irs-2 does regulate the surface expression of glucose transporter 1 (Glut1) as assessed by flow cytometry using a Glut1-specific ligand. Suppression of Glut1 expression inhibits Irs-2-dependent invasion, which links glycolysis to mammary tumor progression. Irs-2 was shown to be important for mammalian target of rapamycin (mTor) activation, and Irs-2-dependent regulation of Glut1 surface expression is rapamycin-sensitive. Collectively, our data indicate that Irs-2, but not Irs-1, promotes invasion by sustaining the aerobic glycolysis of mouse mammary tumor cells and that it does so by regulating the mTor-dependent surface expression of Glut1.

2A1-K02 半導体センサISFETを用いた細胞の代謝活性計測 : HEK293細胞への適用

We evaluated the metabolic activity of HEK 293 cells using a pH/CO_2 sensor system using two ion-sensitive field effect transistors (ISFETs). The system could be utilized to evaluate the production rate of total carbonate and free lactic acid. The quantitative analysis of metabolic switching by the change of glucose concentrations indicated that a decrease of glucose concentration increased total carbonate that represents the cellular respiration activity and decreased free lactic acid that represents glycolysis activity. We analyzed a switching of metabolic pathways from glycolysis to respiration with a decrease of glucose quantitatively in HEK 293 cells for the first time.

External modulation of HT‐1080 human fibrosarcoma cells improves urokinase production

Urokinase was produced in a hollow fiber reactor using HT-1080 human fibrosarcoma cells. External modulation comprised replenishing of the medium in the extracapillary space, reducing the serum concentration in the extracapillary space from 10% to 2% and increasing flow rate of the circulating medium in the intracapillary space from 20 to 80 mL/min, each according to a specific protocol. More than sixfold increase was observed in the cumulative urokinase production for two and three medium replenishing modulations of the extracapillary space. After 15 days of continuous operation, the highest cumulative urokinase obtained was 1.63 x 10(6) PU/mL. SDS-PAGE and zymogram study established that the urokinase obtained was in the high molecular weight range of 54 kDa. The effect of external modulation on cumulative urokinase production was visualized as trajectories with respect to the ratio of lactic acid production rate (LPR) to the glucose uptake rate (GUR). The collective external modulation data showed two separate physiological regions in the cumulative urokinase vs. LPR/GUR plane. The HT-1080 cells exhibited two distinct morphologies in these regions that may be related to acidosis and metastasis. These regions also correspond to low and high urokinase productivity.

Application of a flow-through type pH/CO2 sensor system based on ISFET for evaluation of the glucose dependency of the metabolic pathways in cultured cells

We have previously reported that a flow-through type pH/CO2 sensor system using two ion sensitive field effect transistors (ISFETs) could be utilized to evaluate the production rate of total carbonate (secreted CO2 + secreted bicarbonate ion) and free lactic acid (secreted lactic acid − secreted bicarbonate ion). To validate the usefulness of this system, we applied it to the quantitative analysis of metabolic switching by the change of glucose concentrations in cultured bovine arterial endothelium cell, human umbilical vein endothelium cell and rat cardiac muscle cell. In all of these cell species, a decrease of glucose concentration increased total carbonate that represents the cellular respiration activity and decreased free lactic acid that represents glycolysis activity. We firstly analyzed a switching of metabolic pathways from glycolysis to respiration with a decrease of glucose quantitatively. This ISFET system can be applicable to many biological investigations by analyzing metabolic activity and give dynamic cellular information.

Lactic acid production by Lactobacillus delbrueckii in a dual reactor system using packed bed biofilm reactor

An integrated dual reactor system for continuous production of lactic acid by Lactobacillus delbrueckii using biofilms developed on reticulated polyurethane foam (PUF) is demonstrated. Lactobacillus delbrueckii was immobilized on PUF, packed in a bioreactor and used in lactic acid fermentation. The rate of lactic acid production was significantly high with a volumetric productivity of 5 g l(-1) h(-1) over extended period of time. When coupled to a bioreactor, the system could be operated as dual reactor for over 1000 h continuously without augmentation of inoculum and no compromise on productivity. Polyurethane foams offer an excellent support for biofilm formation. The system was very robust and could be operated for prolonged period at a volumetric productivity of 4-6 g l(-1) h(-1).

Effect of Product Inhibitions on L-Lactic Acid Fermentation From Fresh Cassava Roots in Tofu Liquid Waste by &lt;I&gt;Streptococcus bovis&lt;/I&gt;

The ef fects of product inhibition on lactic acid fermentation from fresh cassava roots in tofu liquid waste by Streptococcus bovis were studied in batch culture. The lactic acid production and growth rate gradually decrease with increase of inhibitor (lactic acid) concentration. The effects of product inhibition on productivity and specific growth rate were confirmed by the Lineweaver-Burk plot to noncompetitive inhibition. The product inhibition was evaluated by two inhibitions constants: inhibition constant for productivity (Ki) and inhibition constant for specific growth rate (Ksi). They decrease with increasing of inhibitor concentration. The values of Ki and Ksi in a rich media are smaller than those in a poor media and the Ki is larger than the Ksi in those media. The experiment results on batch fermentation agree with the noncompetitive inhibition model for about four days, but they deviate from the inhibition model after four days due to high inhibitor concentration. It is supposed that accumulation of lactic acid in broth decidedly causes damage on viable cell.

Selective elimination of mutant mitochondrial genomes as therapeutic strategy for the treatment of NARP and MILS syndromes.

Mitochondrial diseases are not uncommon, and may result from mutations in both nuclear and mitochondrial DNA (mtDNA). At present, only palliative therapies are available for these disorders, and interest in the development of efficient treatment protocols is high. Here, we demonstrate that in cells heteroplasmic for the T8993G mutation, which is a cause for the NARP and MILS syndromes, infection with an adenovirus, which encodes the mitochondrially targeted R.XmaI restriction endonuclease, leads to selective destruction of mutant mtDNA. This destruction proceeds in a time- and dose-dependent manner and results in cells with significantly increased rates of oxygen consumption and ATP production. The delivery of R.XmaI to mitochondria is accompanied by improvement in the ability to utilize galactose as the sole carbon source, which is a surrogate indicator of the proficiency of oxidative phosphorylation. Concurrently, the rate of lactic acid production by these cells, which is a marker of mitochondrial dysfunction, decreases. We further demonstrate that levels of phosphorylated P53 and gammaH2ax proteins, markers of nuclear DNA damage, do not change in response to infection with recombinant adenovirus indicating the absence of nuclear DNA damage and the relative safety of the technique. Finally, some advantages and limitations of the proposed approach are discussed.

Effects of a Mixture of Lactic Acid Bacteria Applied as a Freeze-Dried or Fresh Culture on the Fermentation of Alfalfa Silage

Alfalfa (approximately 31% DM) was untreated or treated with a silage inoculant containing the lactic acid bacteria Lactobacillus lactis, Lactobacillus plantarum L-54, and L. plantarum Aber F1. The inoculant was added at a normal and a high dose as a freeze-dried powder that had been mixed with water just prior to application, or it was grown with nutrients the day before and added as a fresh culture. The actual application rate of lactic acid bacteria was 1.19×105 for the normal dose, 4.30×105 for the high dose, and 5.10×105 for the fresh culture. All inoculated silages showed a faster increase in the rate of lactic acid production and a decrease in the drop in pH over the first 24h of ensiling compared with untreated silage. The effect was greatest for silage treated with the fresh culture and was supported by the fact that this treatment had numbers of lactic acid bacteria that increased faster than in other treatments. Inoculation also generally resulted in a fermentation profile that was more homolactic (more lactic acid and less acetic acid, ethanol, and NH3-N) than for untreated silage, but the effect was greatest for the fresh culture. Inoculation did not affect in vitro neutral detergent fiber digestion or the concentrations of neutral detergent fiber or total N in silages. The recovery of dry matter was greater in silage that was treated with a high level of the freeze-dried culture or with the fresh culture when compared with the untreated control. This study showed that application of a silage inoculant as a freeze-dried culture or as a fresh culture resulted in alfalfa silage with a more homolactic fermentation profile. The effect was greatest from addition of the fresh culture.

Kinetic modeling of lactic acid production from molasses using Enterococcus faecalis RKY1

A kinetic model has been developed for batch fermentation of cane-sugar molasses for lactic acid production by Enterococcus faecalis RKY1. Parameters of the kinetic model have been determined based on experimental data by using genetic algorithm. The values of key kinetic constants are maximum specific growth rate ( μ max), 1.6 h −1, growth-associated constant for lactic acid production ( α), 0.26 g g −1; maximum specific lactic acid production rate ( q p,max), 3 g g −1 h −1; maximum specific sugar utilization rate ( q s,max), 3.33 g g −1 h −1. It has been observed that the growth of biomass and lactic acid production are affected by lactic acid inhibition and it has been taken into account with an exponential term. However, effects of substrate limitation and substrate inhibition have been found to be relatively small. When compared with batch experimental data, the model provides good predictions for growth of biomass, sugar consumption and lactic acid production profiles on media with initial molasses concentration ranging from 130 to 333 g/l with few exceptions. Effect of pH on kinetic parameters has also been studied. It has been found that the growth of biomass and lactic acid production are strongly influenced by pH. Optimum pH is found to be 7.

Properties and acceptability of Som-fug, a Thai fermented fish mince, inoculated with lactic acid bacteria starters

Effect of inoculation of different lactic acid bacteria (LAB) on the fermentation and quality of Som-fug from bigeye snapper was investigated. Som-fug inoculated with Pediococcus acidilactici at 10 4 CFU/g (PA104) had a greater acceptability than those inoculated with Lactobacillus plantarum and Pediococcus pentosaceus at either 10 4 or 10 6 CFU/g and the control (without inoculum). During fermentation, PA104 exhibited a higher rate of fermentation than the control as indicated by the greater rate of pH drop and lactic acid production ( p<0.05). Based on pH desired (pH 4.5), the fermentation was completed within 48 and 36 h for the control and PA104, respectively. Due to higher acid production rate, the textural development of PA104 was more pronounced. Som-fug inoculated with LAB generally exhibited higher hardness and adhesiveness than the control ( p<0.05), when assessed by texture profile analysis (TPA). From the result, inoculation with P. acidilactici resulted in a reduction of fermentation time and improved the quality of Som-fug. Therefore, P. acidilactici can be used as a potential starter for Som-fug fermentation.