Influence of Initial pH Values on the Lag Phase ofEscherichia coliandBacillus licheniformisBatch Cultures

2013 ◽  
Vol 85 (6) ◽  
pp. 863-871 ◽  
Author(s):  
Thomas G. Palmen ◽  
Marco Scheidle ◽  
Robert Huber ◽  
Claudia Kamerke ◽  
Anja Wilming ◽  
...  
Keyword(s):  
Lag Phase ◽  
Ph Values ◽  
Initial Ph

Growth and Aflatoxin Production by Aspergillus parasiticus NRRL 2999 in the Presence of Potassium Benzoate or Potassium Sorbate and at Different Initial pH Values

1987 ◽  
Vol 50 (10) ◽  
pp. 820-825 ◽  
Author(s):  
GULAM RUSUL ◽  
ELMER H. MARTH
Keyword(s):  
High Performance ◽  
Aspergillus Parasiticus ◽  
Ph Value ◽  
Aflatoxin Production ◽  
Reversed Phase ◽  
Potassium Sorbate ◽  
Lag Phase ◽  
Ph Values ◽  
Initial Ph ◽  
Potassium Benzoate

Experiments were done to determine how different concentrations of potassium benzoate or potassium sorbate in a glucose-yeast extract-salts medium with an initial pH value of 3.5, 4.5 or 5.5 affected growth and aflatoxin production by Aspergillus parasiticus NRRL 2999. The pH of the medium, weight of mycelium and amount of aflatoxin produced were determined after 3 and 7 d of incubation. Aflatoxin was determined using reversed-phase high-performance liquid chromatography. Maximum concentrations of potassium sorbate and potassium benzoate that permitted growth were 0.2% and 0.4%, respectively, in a medium with an initial pH of 5.5. When the initial pH was 4.5, the maximum concentrations of potassium sorbate and potassium benzoate that permitted growth were 0.05% and 0.10%, respectively, but there was an extended lag phase. Increasing concentrations of potassium benzoate or potassium sorbate decreased amounts of aflatoxin B1 and G1 produced after 3 d in a medium with initial pH values of 5.5 or 4.5. Cultures growing in the medium containing 0.1, 0.15 or 0.20% potassium benzoate or potassium sorbate and with an initial pH of 5.5 were somewhat inhibited at 3 d of incubation, which was characterized by a slow decrease in pH, low mycelium dry weight and small amounts of accumulated aflatoxins. After 7 d these cultures overcame the initial inhibition and produced substantial amounts of aflatoxins and mycelium. This was also true for cultures growing in a medium with an initial pH of 4.5 and containing potassium benzoate or potassium sorbate. By decreasing the initial pH of the medium from 5.5 to 4.5, amounts of potassium benzoate or potassium sorbate required to achieve inhibition decreased by a factor of 10.

Treatment of cooling tower blowdown water containing silica, calcium and magnesium by electrocoagulation

2009 ◽  
Vol 60 (9) ◽  
pp. 2345-2352 ◽  
Author(s):  
Z. Liao ◽  
Z. Gu ◽  
M. C. Schulz ◽  
J. R. Davis ◽  
J. C. Baygents ◽  
...  
Keyword(s):  
Cooling Tower ◽  
Target Species ◽  
Organic Additives ◽  
Dissolved Silica ◽  
Ion Removal ◽  
Ph Values ◽  
Silica Removal ◽  
Initial Ph ◽  
Aluminum Electrodes ◽  
Calcium And Magnesium

This research investigated the effectiveness of electrocoagulation using iron and aluminium electrodes for treating cooling tower blowdown (CTB) waters containing dissolved silica (Si(OH)4), Ca2 +  and Mg2 + . The removal of each target species was measured as a function of the coagulant dose in simulated CTB waters with initial pH values of 5, 7, and 9. Experiments were also performed to investigate the effect of antiscaling compounds and coagulation aids on hardness ion removal. Both iron and aluminum electrodes were effective at removing dissolved silica. For coagulant doses ≤3 mM, silica removal was a linear function of the coagulant dose, with 0.4 to 0.5 moles of silica removed per mole of iron or aluminium. Iron electrodes were only 30% as effective at removing Ca2 +  and Mg2 +  as compared to silica. There was no measurable removal of hardness ions by aluminium electrodes in the absence of organic additives. Phosphonate based antiscaling compounds were uniformly effective at increasing the removal of Ca2 +  and Mg2 +  by both iron and aluminium electrodes. Cationic and amphoteric polymers used as coagulation aids were also effective at increasing hardness ion removal.

scholarly journals Characterization of Melanoidins and Color Development in Dulce de Leche, a Confectionary Dairy Product With High Sucrose Content: Evaluation of pH Effect, an Essential Manufacturing Process Parameter

2021 ◽  
Vol 8 ◽  
Author(s):  
Analía Rodríguez ◽  
Patricia Lema ◽  
María Inés Bessio ◽  
Guillermo Moyna ◽  
Cristina Olivaro ◽  
...  
Keyword(s):  
Enzymatic Hydrolysis ◽  
Ph Effect ◽  
Dairy Product ◽  
Gel Filtration ◽  
Significant Degree ◽  
Product Analysis ◽  
Molecular Weights ◽  
Ph Values ◽  
Initial Ph

The effect on color of the initial pH employed in dulce de leche (DL) production was evaluated through physicochemical and spectroscopical characterization of the melanoidins formed in the process. Melanoidins originated at pH values of 6.5, 7.0, and 7.5, and they were released by the enzymatic hydrolysis of the protein backbone and purified by gel filtration. They showed a significant degree of polydispersity, in general, with molecular weights (MWs) below 1,800 Da. DL produced at a higher pH released melanoidins with higher average MW after the enzymatic hydrolysis. They also presented darker colors (dE*ab, C*), more closely resembling those typical of the commercial product. Analysis of the fractions isolated by gel filtration using HPLC-DAD and multinuclear NMR showed an heterogeneous and complex composition. Even though structurally related, the 1H NMR spectra of melanoidins showed a higher degree of aromaticity at higher pH values. In conclusion, the pH employed in DL production affects the amount and structure of the colored products originated by MR reactions, and thus the color of the final product.

A bicarbonate-containing medium for the solution culture of submersed plants

1993 ◽  
Vol 71 (12) ◽  
pp. 1584-1588 ◽  
Author(s):  
Craig S. Smith
Keyword(s):  
Aquatic Plants ◽  
Plant Pathogens ◽  
Myriophyllum Spicatum ◽  
Hard Water ◽  
Solution Culture ◽  
Water Medium ◽  
Vallisneria Americana ◽  
Culture Techniques ◽  
Ph Values ◽  
Initial Ph

A bicarbonate-buffered hard-water medium was evaluated for the solution (nonrooted) culture of submersed aquatic plants. The new medium had an initial pH of 8.2, and after 2 weeks of plant growth in it, pH values remained similar to those in hard-water lakes. Several plants from hard-water lakes grew more rapidly in the new medium than in the commonly used Gerloff medium. When cultures were aerated with air, Myriophyllum spicatum growth was nearly twice as great in the new medium as in Gerloff medium, and growth of Vallisneria americana and Elodea canadensis in the new medium was 4 and 13 times that in Gerloff medium, respectively. When both cultures were aerated with 1% CO2, growth rates of M. spicatum and E. canadensis in the new medium were not distinguishable from those in Gerloff medium, but the growth of V. americana was 40% greater in the new medium. Myriophyllum spicatum was much less susceptible to attack by the fungal pathogen Colletotrichum gloeosporioides in the new medium than in Gerloff medium, similar to the susceptibility shown in nutrient-amended lake water. Key words: aquatic plants, culture techniques, plant pathogens.

Growth of Staphylococcus aureus and Enterotoxin Production in Homemade Mayonnaise Prepared with Different pH Values

1987 ◽  
Vol 50 (10) ◽  
pp. 872-875 ◽  
Author(s):  
ESPERANZA GOMEZ-LUCIA ◽  
JOAQUIN GOYACHE ◽  
JOSE L. BLANCO ◽  
JOSE F. F. GARAYZABAL ◽  
JOSE A. ORDEN ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Ph Values ◽  
Enterotoxin Production ◽  
Initial Ph

The ability of Staphylococcus aureus to grow and produce enterotoxins in homemade mayonnaise prepared at different pH values was studied. Ten enterotoxigenic strains, producing one or two enterotoxin types (A, B, C, or D) were inoculated into mayonnaise samples with pH adjusted to values ranging between 4.0 and 5.8, and incubated at 37°C for 7 d. Counts were made on days 1, 3, 5, and 7 and extracts were prepared on day 7 to detect enterotoxin by ELISA. An important difference was seen between those samples prepared with pH below or equal to 4.9 and those over or equal to 5.0; in the range of pH between 4.0 and 4.9 the average of staphylococcal population was 100 CFU/g; at pH 5.0 it was 1.6 × 105, and at pH 5.15 and above it was at least 8 × 106 CFU/g. Enterotoxin was detected only at initial pH over 5.15 and when final pH was not less than 4.7. The highest amount of enterotoxin corresponded to 157.8 ng of SEB/100 g of mayonnaise.

Growth and Aflatoxin Production by Aspergillus parasiticus NRRL 2999 in the Presence of Acetic or Propionic Acid and at Different Initial pH Values

1987 ◽  
Vol 50 (11) ◽  
pp. 909-914 ◽  
Author(s):  
GULAM RUSUL ◽  
FATHY E. EL-GAZZAR ◽  
ELMER H. MARTH
Keyword(s):  
Acetic Acid ◽  
Propionic Acid ◽  
Aflatoxin B1 ◽  
Maximum Concentration ◽  
Aspergillus Parasiticus ◽  
Dry Weight ◽  
Aflatoxin Production ◽  
Lag Phase ◽  
Significant Difference ◽  
Initial Ph

Experiments were done to determine effects of different concentrations of acetic or propionic acid in a glucose-yeast extract-salts medium with an initial pH value of 4,5 or 5.5 on growth and aflatoxin production by Aspergillus parasiticus NRRL 2999. Amounts of aflatoxin were measured with reversed-phase high-performance liquid chromatography. The maximum concentration of acetic or propionic acid that permitted growth at an initial pH of 5.5 was 1% after 7 d of incubation and 0.25% after 3 d of incubation, respectively. When the initial pH of the medium was 4.5, the maximum concentration of acetic or propionic acid that permitted growth was 0.25 or 0.1%, respectively. There was no significant difference (p>0.05) in amount of mycelial (dry weight) produced by cultures in the presence of 0.0, 0.25, 0.50 or 0.75% acetic acid. Amounts of aflatoxin B1 and G1 produced decreased with an increasing concentration of acetic acid. Increasing concentrations of propionic acid caused a decrease in the amount of mycelial dry weight and aflatoxin produced by cultures growing in the medium with an initial pH of 5.5. At an initial pH of 4.5 mycelial growth was slow and at 3 d of incubation amounts of aflatoxin B1 and G1 produced were reduced as concentrations of acetic acid increased. This also was true for propionic acid in the medium with an initial pH of 4.5. Cultures with an extended lag phase in the presence of acetic or propionic acid overcame this and then produced large amounts of aflatoxin B1 and G1 at 7 and 10 d of incubation.

Histamine and Tyramine Production by a Lactobacillus Strain Subjected to External pH Decrease

1994 ◽  
Vol 57 (3) ◽  
pp. 259-262 ◽  
Author(s):  
RIITTA MAIJALA
Keyword(s):  
Lactic Acid ◽  
Room Temperature ◽  
Lactobacillus Strain ◽  
Ph Values ◽  
Initial Ph ◽  
Ph Decrease ◽  
In The Beginning ◽  
Influence Of Ph ◽  
External Ph ◽  
Made In

The preservative effect of fermentation is based on the pH decrease during processing. However, most studies conceming the influence of pH on the formation of biogenic amines have been made in broths with different initial pH values. A histamine- and tyramine-positive Lactobacillus strain isolated from dry sausage was added at an initial level of 3.9- to 4.4-logl0 CFU/ml and incubated on a shaker at room temperature (20.0°C) for 6 days. The pH was decreased in histidine- or tyrosine-fortified MRS broth by adding glucono-delta-lactone (GDL) or lactic acid during the incubation. The external acidification decreased the growth and the production of histamine and tyramine by the strain. GDL was more effective as a preventative than lactic acid. According to these results, a rapid pH decrease resulting in decreased growth of amine-positive lactic acid bacteria in the beginning of fermentation may be a means of preventing the formation of high levels of amines in foods.

Evolution of carbohydrate fraction in carbonated fermented milks as affected by β-galactosidase activity of starter strains

2002 ◽  
Vol 69 (1) ◽  
pp. 125-137 ◽  
Author(s):  
MIGUEL GUEIMONDE ◽  
NIEVES CORZO ◽  
GABRIEL VINDEROLA ◽  
JORGE REINHEIMER ◽  
CLARA G. DE LOS REYES-GAVILÁN
Keyword(s):  
Lactobacillus Casei ◽  
Streptococcus Thermophilus ◽  
Bifidobacterium Bifidum ◽  
Lactose Hydrolysis ◽  
Activity Levels ◽  
Refrigerated Storage ◽  
Galactosidase Activity ◽  
Continuous Increase ◽  
Ph Values ◽  
Initial Ph

The influence of carbonation on the evolution of lactose, galactose and glucose in fermented milks with added probiotic bacteria (Lactobacillus casei, Lactobacillus acidophilus and/or Bifidobacterium bifidum) was evaluated and related to β-galactosidase activity of starter strains. During incubation and first days of refrigeration, lactose hydrolysis resulting in the liberation of galactose and glucose occurred in CT (Streptococcus thermophilus/Lb. casei), AT (Str. thermophilus/Lb. acidophilus) and ABT fermented milks (Str. thermophilus/Lb. acidophilus/Bifid. bifidum). Levels of galactose were higher than those of glucose and could be related to the preferential consumption of glucose by actively growing bacteria. Through the incubation, lactose and monosaccharide levels were not affected by milk carbonation. However, during refrigerated storage the presence of this gas was associated with slightly lower content of lactose and higher levels of galactose and glucose in AT and ABT products but not in CT fermented milks. Through the refrigeration galactose was moderately utilised by Lb. acidophilus in AT products whereas the presence of Bifid. bifidum seems to prevent the consumption of this sugar in ABT fermented milks. Glucose remained constant, with minor variations in CT products but a continuous increase of this sugar occurred in carbonated AT and ABT fermented milks during storage. β-Galactosidase activity displayed by Str. thermophilus strains was similar at pH 6·5 (initial pH of non-carbonated samples) and pH 6·3 (initial pH of carbonated samples) whereas Lb. acidophilus LaA3 showed greater β-galactosidase activity at pH 6·3 than at higher pH values. Thus, the enhanced metabolic activity of Lb. acidophilus caused by the low initial pH of carbonated milk also promoted higher cellular β-galactosidase activity that could have released greater amounts of galactose and glucose from lactose in AT and ABT fermented milks through the refrigerated period. In CT fermented milks, similar β-galactosidase activity levels of Str. thermophilus at pH 6·5 and 6·3 together with the absence of β-galactosidase activity in Lb. casei could explain the lack of differences on glucose and galactose content between carbonated and non-carbonated samples.

Effect of operational pH on biohydrogen production from food waste using anaerobic batch reactors

2014 ◽  
Vol 69 (9) ◽  
pp. 1886-1893 ◽  
Author(s):  
Chaeyoung Lee ◽  
Sewook Lee ◽  
Sun-Kee Han ◽  
Sunjin Hwang
Keyword(s):  
Food Waste ◽  
Fish Analysis ◽  
Batch Reactors ◽  
Clostridium Species ◽  
Ph Values ◽  
Species Cluster ◽  
Initial Ph ◽  
H2 Yield ◽  
Total Bacteria

This study was performed to investigate the influence of operational pH on dark H2 fermentation of food waste by employing anaerobic batch reactors. The highest maximum H2 yield was 1.63 mol H2/mol hexoseadded at operational pH 5.3, whereas the lowest maximum H2 yield was 0.88 mol H2/mol hexoseadded at operational pH 7.0. With decreasing operational pH values, the n-butyrate concentration tended to increase and the acetate concentration tended to decrease. The highest hydrogen conversion efficiency of 11.3% was obtained at operational pH 5.3, which was higher than that (8.3%) reported by a previous study (Kim et al. (2011) ‘Effect of initial pH independent of operational pH on hydrogen fermentation of food waste’, Bioresource Technology 102 (18), 8646–8652). The new result indicates that the dark fermentation of food waste was stable and efficient in this study. Fluorescence in situ hybridization (FISH) analysis showed that Clostridium species Cluster I accounted for 84.7 and 13.3% of total bacteria at operational pH 5.3 and pH 7.0, respectively, after 48 h operation.

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