Response of Cultures of Propionibacterium to Acid and Low pH: Tolerance and Inhibition

1998 ◽  
Vol 61 (2) ◽  
pp. 211-216 ◽  
Author(s):  
JILL L. REHBERGER ◽  
BONITA A. GLATZ
Keyword(s):  
Hydrochloric Acid ◽  
Propionic Acid ◽  
Low Ph ◽  
The Other ◽  
Propionibacterium Acidipropionici ◽  
Ph Values ◽  
Neutral Ph ◽  
Ph Tolerance ◽  
Propionibacterium Thoenii ◽  
Ph Conditions

Seventeen Propionibacterium strains were tested for acid production and final pH achieved on glucose, fructose, or maltose as the primary carbon source. On average, strains of Propionibacterium acidipropionici produced more acid and reached lower final pH values than did strains of the other species. Three strains of P. acidipropionici, one Propionibacterium jensenii, and two Propionibacterium thoenii strains were tested further for the ability to survive and/or grow at low pH with lactic, hydrochloric, or propionic acid as acidulant. The organic acids were more inhibitory than hydrochloric acid; propionic acid was most inhibitory. In all cases, the P. jensenii and P. thoenii strains initiated growth and survived at lower pH values than did the P. acidipropionici strains. The ability to produce large amounts of acid or achieve low final pH values did not coincide with the ability to initiate growth or survive in low-pH conditions. Strains could not initiate growth below pH 5.0, but cultures started at neutral pH reached final pH values of less than 4.4. At neutral pH, strains could grow in the presence of increased lactate concentrations (up to 180 mM) or propionate concentrations (150 mM) that were inhibitory at acid pH. Attempts to isolate variants able to initiate growth below pH 5.0 were unsuccessful.

GROWTH OF STAPHYLOCOCCUS AUREUS IN ACIDIFIED PASTEURIZED MILK1

1970 ◽  
Vol 33 (11) ◽  
pp. 516-520 ◽  
Author(s):  
T. E. Minor ◽  
E. H. Marth
Keyword(s):  
Staphylococcus Aureus ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Hydrochloric Acid ◽  
Ph Value ◽  
The Other ◽  
Antagonistic Effects ◽  
Pasteurized Milk ◽  
Ph Values ◽  
Effect On Growth

The effect of gradually reducing the pH of pasteurized milk with acetic, citric, hydrochloric, lactic, and phosphoric acids over periods of 4, 8, and 12 hr on growth of Staphylococcus aureus 100 in this substrate was determined. In addition, 1: 1 mixtures of lactic acid and each of the other acids, and of acetic and citric acids were evaluated for their effect on growth of this organism. To achieve a 90% reduction in growth over a 12 hr period, a final pH value of 5.2 was required for acetic, 4.9 for lactic, 4.7 for phosphoric and citric, and 4.6 for hydrochloric acid. A 99% reduction during a 12 hr period was obtained with a final pH value of 5.0 for acetic, 4.6 for lactic, 4.5 for citric, 4.1 for phosphoric, and 4.0 for hydrochloric acid. A pH value of 3.3 was required for a 99.9% reduction with hydrochloric acid, whereas the same effect was produced at a pH value of 4.9 with acetic acid. Correspondingly lower pH values were required to inhibit growth within 8 and 4 hr periods. Mixtures of acids adjusted to pH values at the borderline for growth (12 hr period) exhibited neither synergistic nor antagonistic effects between two acids.

Effect of pH on Glycolate and Ammonia Excretion in L-MSO Treated Chlorella Cells

1987 ◽  
Vol 42 (5) ◽  
pp. 525-529
Author(s):  
Yoshihiro Shiraiwa ◽  
Georg H. Schmid
Keyword(s):  
Chlorella Vulgaris ◽  
Major Part ◽  
Ammonia Excretion ◽  
Low Ph ◽  
Final Concentration ◽  
The Other ◽  
Effect Of Ph ◽  
Photosynthetic Rates ◽  
Ph Values ◽  
Glycolate Metabolism

Abstract The effect of pH changes on the excretion of ammonia and glycolate from algal cells into the medium was investigated in L-MSO (final concentration, 0.5 mм) -treated High-and Low CO2-cells of Chlorella vulgaris 211-11 h. The excretion was analyzed in the condition in which the cells were continuously gassed with air at 25 °C. At the values tested, generally more ammonia was excreted in L-MSO-treated Low CO2-cells than in L-MSO treated High CO2-cells. In both kinds of algal cells more ammonia was excreted at low pH-values and absolutely no ammonia was excreted at pH 8. In the dark, no or only slight ammonia excretion was observed in both L-MSO-treated High and Low CO2-cells. Under all these conditions no or only very low glycolate excretion was observed in both L-MSO treated High and Low CO2-cells. In High CO2-cells rates of photosynthesis were high at pH 6 and lower at higher pH values. On the other hand Low CO2-cells showed practically little dependence of photosynthetic rates on the pH. This result might indicate that the major part of the ammonia excretion observed, was not due to the inhibition of photosynthesis at acid pH values. It is known that ammonia excretion in L-MSO treated algal cells is due to the inhibition of the refixation of ammonia which originates from the glycine-serine aminotransferase reaction in the glycolate pathway. Our results demonstrate that glycolate production and glycolate metabolism are more intense at low pH values when compared to high pH values. This is valid for both High and Low CO2-cells. Low CO2-cells in Chlorella vulgaris 211-11 h exhibit a more active glycolate metabolism than High CO2-cells.

scholarly journals An Acid-activated Nucleobase Transporter from Leishmania major

2009 ◽  
Vol 284 (24) ◽  
pp. 16164-16169 ◽  
Author(s):  
Diana Ortiz ◽  
Marco A. Sanchez ◽  
Hans P. Koch ◽  
H. Peter Larsson ◽  
Scott M. Landfear
Keyword(s):  
Leishmania Major ◽  
De Novo ◽  
Low Ph ◽  
Acidic Ph ◽  
Physiological Conditions ◽  
Neutral Ph ◽  
Amastigote Stage ◽  
Electrode Voltage ◽  
Ph Conditions ◽  
Micromolar Range

Parasitic protozoa are unable to synthesize purines de novo and must import preformed purine nucleobases or nucleosides from their hosts. Leishmania major expresses two purine nucleobase transporters, LmaNT3 and LmaNT4. Previous studies revealed that at neutral pH, LmaNT3 is a broad specificity, high affinity nucleobase transporter, whereas LmaNT4 mediates the uptake of only adenine. Because LmaNT4 is required for optimal viability of the amastigote stage of the parasite that lives within acidified phagolysomal vesicles of mammalian macrophages, the function of this permease was examined under acidic pH conditions. At acidic pH, LmaNT4 acquires the ability to transport adenine, hypoxanthine, guanine, and xanthine with Km values in the micromolar range, indicating that this transporter is activated at low pH. Thus, LmaNT4 is an acid-activated purine nucleobase transporter that functions optimally under the physiological conditions the parasite is exposed to in the macrophage phagolysosome. In contrast, LmaNT3 functions optimally at neutral pH. Two-electrode voltage clamp experiments performed on LmaNT3 and LmaNT4 expressed in Xenopus oocytes revealed substrate-induced inward directed currents at acidic pH, and application of substrates induced acidification of the oocyte cytosol. These observations imply that LmaNT3 and LmaNT4 are nucleobase/proton symporters.

Hydrothermal crystallization kinetics of m-ZrO2 and t-ZrO2

1990 ◽  
Vol 5 (11) ◽  
pp. 2698-2705 ◽  
Author(s):  
Raymond P. Denkewicz ◽  
Kevor S. TenHuisen ◽  
James H. Adair
Keyword(s):  
Crystallization Kinetics ◽  
Low Ph ◽  
Formation Mechanisms ◽  
Gel Structure ◽  
Hydrothermal Conditions ◽  
High Ph ◽  
Ph Values ◽  
Ph Conditions ◽  
Apparent Activation Energies ◽  
Kinetics Of

The isothermal nucleation and crystallization kinetics of hydrothermally prepared monoclinic and tetragonal ZrO2 have been determined at various pH conditions. It is shown that monoclinic ZrO2 precipitates at low pH whereas at high pH tetragonal ZrO2 crystallizes from an amorphous zirconium (hydrous) oxide, Zr(OH)xOy, precursor. At intermediate pH conditions mixtures of the polymorphs are formed suggestive of kinetically competing particle formation mechanisms. The data are explained by the proposed existence of three controlling regimes for the formation of crystalline ZrO2: dissolution/precipitation at low pH, a solubility controlled regime at intermediate pH values, and a gel structure controlled regime at high pH. Apparent activation energies for the nucleation and crystallization of monoclinic and tetragonal ZrO2 formed under hydrothermal conditions are presented.

Electronic and Raman spectroscopic studies of copper adrenalin complexes and copper induced compounds

1976 ◽  
Vol 54 (24) ◽  
pp. 3815-3823 ◽  
Author(s):  
Mohammed S. Rahaman ◽  
Stephen M. Korenkiewicz
Keyword(s):  
Free Radical ◽  
Hydrochloric Acid ◽  
Raman Spectra ◽  
Spectroscopic Studies ◽  
Low Ph ◽  
Basic Solution ◽  
High Ph ◽  
Raman Spectroscopic ◽  
Ph Values

Electronic and Raman spectra of adrenalin–copper(II) complexes and copper catalyzed compounds have been studied. Adrenalin reacts with copper(II) ion at pH 9.2 and higher to produce a very short lived violet free radical, a brown adrenochrome, a yellow conjugated salt, indolyl-indoquinone, and melanin. Results indicate that copper does not form complexes with adrenalin in basic solution. Between pH 6.5 and 8.5 adrenalin transforms into adrenochrome in presence of copper. The adrenochrome in 1.5 N hydrochloric acid produces the conjugate salt that is produced in the solution of high pH. At low pH values, between pH 4.0 to 5.5, adrenalin forms a brown complex with copper(II). Copper is entirely chelated to the phenolic groups of the amines. The complex in 1.5 N hydrochloric acid produces a black polymeric pigment.

scholarly journals pH-dependent interconversion of two forms of tyrosinase in human skin

1988 ◽  
Vol 252 (2) ◽  
pp. 481-487 ◽  
Author(s):  
R K Tripathi ◽  
C Chaya Devi ◽  
A Ramaiah
Keyword(s):  
Human Skin ◽  
Sodium Phosphate ◽  
Inhibitory Concentration ◽  
Low Ph ◽  
The Other ◽  
Gradual Change ◽  
Ph Values ◽  
Sodium Phosphate Buffer ◽  
Solubilized Enzyme ◽  
Ph Dependent

1. We have shown that the characteristic lag in cresolase activity of human skin tyrosinase at inhibitory concentration of tyrosine was absent at all pH values studied, i.e. pH 5.2, 5.7, 6.2 and 6.8, if the enzyme solubilized at low pH was used as the source of enzyme, but the same enzyme when dialysed against buffers of various pH values showed linear activity only at pH 5.2 and was not inhibited by excess tyrosine, whereas at higher pH values it exhibited a lag and inhibition by excess tyrosine. 2. However, the enzyme solubilized in buffer/detergent, pH 6.8, when dialysed against buffer of the same pH showed linear activity at pH 5.2 and non-linear activity at pH 6.8. 3. The water/detergent-solubilized enzyme from human skin melanosomes showed linear activity even at inhibitory concentrations of tyrosine at pH 5.2 and 6.8 up to 2 h, but acceleration of rate was observed after 2 h for the enzyme measured at pH 6.8. 4. After dialysis of the water/detergent-solubilized enzyme against double-glass-distilled water, it still exhibits linear activity at inhibitory concentration of tyrosines at pH 6.8 for the first 2 h, but the same enzyme when dialysed against 0.02 M-sodium phosphate buffer, pH 6.8, exhibits negligible activity up to 1/2 h, in contrast with considerable activity before dialysis during the same interval of time, but without any loss of activity at later intervals of incubation time. 5. On the basis of these results, it is concluded that the enzyme exists in at least two interconvertible forms, one without lag and inhibition by excess tyrosine and the other with lag and inhibition by excess tyrosine. These two forms are interconvertible only by gradual change in pH over a period of hours.

scholarly journals pH Tolerance in Freshwater Bacterioplankton: Trait Variation of the Community as Measured by Leucine Incorporation

2015 ◽  
Vol 81 (21) ◽  
pp. 7411-7419 ◽  
Author(s):  
Erland Bååth ◽  
Emma Kritzberg
Keyword(s):  
Bacterial Growth ◽  
Low Ph ◽  
Tolerance Index ◽  
Response Curves ◽  
Trait Variation ◽  
High Ph ◽  
Ph Values ◽  
Ph Tolerance ◽  
Community Tolerance

ABSTRACTpH is an important factor determining bacterial community composition in soil and water. We have directly determined the community tolerance (trait variation) to pH in communities from 22 lakes and streams ranging in pH from 4 to 9 using a growth-based method not relying on distinguishing between individual populations. The pH in the water samples was altered to up to 16 pH values, coveringin situpH ± 2.5 U, and the tolerance was assessed by measuring bacterial growth (Leu incorporation) instantaneously after pH adjustment. The resulting unimodal response curves, reflecting community tolerance to pH, were well modeled with a double logistic equation (meanR2= 0.97). The optimal pH for growth (pHopt) among the bacterial communities was closely correlated within situpH, with a slope (0.89 ± 0.099) close to unity. The pH interval, in which growth was ≥90% of that at pHopt, was 1.1 to 3 pH units wide (mean 2.0 pH units). Tolerance response curves of communities originating from circum-neutral pH were symmetrical, whereas in high-pH (8.9) and especially in low-pH (<5.5) waters, asymmetric tolerance curves were found. In low-pH waters, decreasing pH was more detrimental for bacterial growth than increasing pH, with a tendency for the opposite for high-pH waters. A pH tolerance index, using the ratio of growth at only two pH values (pH 4 and 8), was closely related to pHopt(R2= 0.83), allowing for easy determination of pH tolerance during rapid changes in pH.

scholarly journals Does the natural carcinogen ptaquiloside degrade readily in groundwater?

2021 ◽  
Vol 33 (1) ◽  
Author(s):  
Jane S. Wu ◽  
Frederik Clauson-Kaas ◽  
Dan Nybro Lindqvist ◽  
Lars Holm Rasmussen ◽  
Bjarne W. Strobel ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Drinking Water ◽  
Degradation Kinetics ◽  
Low Ph ◽  
Experimental Conditions ◽  
Neutral Ph ◽  
Rate Of Hydrolysis ◽  
Acidic Conditions ◽  
Ph Conditions ◽  
Ph Range

Abstract Background Ptaquiloside (PTA) is a natural carcinogen found in bracken ferns. PTA is released from the plants via soil to surface and groundwaters from where humans can be exposed via drinking water. Primary degradation of PTA is due to hydrolysis with formation of pterosin B (PTB). Temperature and pH determine the rate of hydrolysis under pure experimental conditions. To assess the applicability of the experimental model to natural groundwaters, PTA degradation kinetics were examined in a range of natural groundwaters at environmentally relevant conditions. Results PTA was quantified by UPLC-MS/MS. Over an 80-day study period, PTA half-lives ranged from 6.5 to 47 days (natural pH; 8.0 °C). The fastest degradation was observed for the most alkaline groundwaters with pH of around 8. Rates of degradation were well predicted using an existing mathematical model for hydrolysis. However, deviations from this model were found, especially at the extremes of the examined pH-range (4.7–8.2). The degree of conversion of PTA to PTB was close to unity around neutral pH. However, at slightly acidic conditions, formation of PTB could only count for 9% of the degraded PTA, indicating formation of other products. Conclusions Degradation of PTA in groundwater is determined by pH and temperature, and PTA can prevail for months under slightly acid to neutral pH conditions. The existing laboratory-based model for PTA hydrolysis is generally applicable for groundwaters but needs further validation at high and low pH.

scholarly journals Shelf life of minimally processed pineapples treated with ascorbic and citric acids

Bragantia ◽  
2012 ◽  
Vol 71 (3) ◽  
pp. 447-453 ◽  
Author(s):  
Lucimara Rogéria Antoniolli ◽  
Benedito Carlos Benedetti ◽  
Men de Sá Moreira de Souza Filho ◽  
Deborah dos Santos Garruti ◽  
Maria de Fátima Borges
Keyword(s):  
Ascorbic Acid ◽  
Shelf Life ◽  
Respiratory Activity ◽  
Low Ph ◽  
The Other ◽  
Water Control ◽  
Minimally Processed ◽  
Ph Values ◽  
Physical Chemical ◽  
Polyethylene Terephtalate

The purpose of this research was to determine the shelf life of minimally processed (MP) 'Pérola' pineapples treated with ascorbic acid (AA) and citric acid (CA) based on physical, chemical, sensorial and microbiological attributes. Slices were dipped into drinking water (control) or combined solutions of AA:CA (%) (1.0:0.5 and 1.0:1.0) with sodium hypochlorite (NaClO 20 mg L-1) for 30 seconds. The samples were conditioned in polyethylene terephtalate packages and stored at 4±1 °C per 13 days. The low peroxidase activity in the slices treated with antioxidant combinations was related to low pH values observed in these samples. The treatments 1.0:0.5 and 1.0:1.0 (AA:CA, %) favored maintenance of the initial a* values and avoided the pulp browning. The ascorbic acid increased more than double on the 2nd day in the treated slices. By the 4th day the CO2 values suggested a higher respiratory activity in the slices treated with anti-browning compounds. The antioxidant treatments did not produce detectable residual flavors in the MP pineapple. Regardless of microbiological safety during the 13 days of cold storage, the control slices can be kept by 6 days, afterwards the color and dehydration become strong enough to affect the appearance. On the other hand, MP 'Pérola' pineapples treated with 1.0:0.5 (AA:CA, %) and NaClO (20 mg L-1) can be stored for 8 days at 4±1 ºC, which represents the extension of the shelf life in 2 days. After this period the overripe odor starts to develop.

THE EFFECT OF NITROGEN AND PHOSPHORUS NUTRITION ON pH OF TOMATO

1966 ◽  
Vol 46 (6) ◽  
pp. 681-684 ◽  
Author(s):  
J. S. Matthews ◽  
L. G. Denby
Keyword(s):  
Low Ph ◽  
The Other ◽  
Phosphorus Nutrition ◽  
Nitrogen And Phosphorus ◽  
Tomato Fruits ◽  
High Ph ◽  
Ph Values ◽  
Low Levels ◽  
Nutrient Solutions

Tomato fruits, grown under glass in inert media, and supplied with nutrient solutions containing high and low levels of N and P, varied in pH from 4.21 to 4.61. Fruits from plants receiving low levels of both nutrients consistently had low pH values. Those from plants fed high levels of P or N had high pH whenever the level of the other element was not limiting.

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