Influence of pH and Incubation Time on Ochratoxin A Production by Aspergillus carbonarius in Culture Media

2005 ◽  
Vol 68 (7) ◽  
pp. 1435-1440 ◽  
Author(s):  
A. ESTEBAN ◽  
M. L. ABARCA ◽  
M. R. BRAGULAT ◽  
F. J. CABAÑES
Keyword(s):  
Ochratoxin A ◽  
Culture Media ◽  
Aspergillus Carbonarius ◽  
Yeast Autolysate ◽  
Initial Ph ◽  
Wide Ph Range ◽  
Ph Range ◽  
Incubation Temperatures ◽  
Influence Of Ph ◽  
Czapek Yeast Autolysate Agar

The effect of pH (2 to 10) and temperature (15 and 30°C) on growth and production of ochratoxin A (OTA) of six strains of Aspergillus carbonarius was studied in two culture media: Czapek yeast autolysate agar and yeast extract sucrose agar. Isolates were selected by their different source and different reported ability to produce OTA. Regardless of the initial pH or the temperature tested, Czapek yeast autolysate agar has been shown to be the best culture medium for OTA production by A. carbonarius. In this medium, OTA was produced from pH 2 to 10 at the two incubation temperatures tested. The results obtained show the ability of A. carbonarius to not only grow but also produce OTA over a wide pH range at high or low temperatures. This may help explain why this species is considered the main OTA source in some substrata.

Chemical control of fungal growth and ochratoxin A production by Aspergillus isolated from Moroccan grapes

2018 ◽  
Vol 7 (2) ◽  
pp. 84-91
Author(s):  
Adil Laaziz ◽  
Souad Qjidaa ◽  
Yousra El Hammoudi ◽  
Abdelouahed Hajjaji ◽  
Amina Bouseta
Keyword(s):  
Ochratoxin A ◽  
Radial Growth ◽  
Culture Medium ◽  
Fungal Growth ◽  
Sublethal Concentration ◽  
Agar Culture ◽  
Total Inhibition ◽  
Yeast Autolysate ◽  
Germination And Growth ◽  
Czapek Yeast Autolysate Agar

The aim of this study was to evaluate the effect of three fungicides azoxystrobin (Ortiva), hexaconazole (Hexa) and pyrimethanil (Pyrus) for their ability to inhibit the radial growth and ochratoxin A (OTA) production by five ochratoxigenic strains of Aspergillus carbonarius and A. niger previously iso-lated from Moroccan grapes. Our results showed that, the addition of the fungicides to the Czapek Yeast Autolysate agar culture medium reduced the growth of the ochratoxigenic strains. Pyrimethanil caused total inhibition of spore germination and growth of the five strains, for all dose tested. Where-as hexaconazole totally inhibited the growth of 4 strains and gave growth for the MUCL 49227 strain (2.67 mm/day) at sublethal concentration. The reduction in radial growth was less marked for azoxystrobin, with growth rate varying between 0 and 6.37 mm/day depending on the strain and the azoxystrobin concentration. Analysis of variance showed that the effect of single factors (fungicides, concentration and strain) and their interactions on growth and OTA production were highly significant (P=0.000).These findings suggest that the use of tested fungicides have to potential for reduction in production of OTA.

scholarly journals Organic/Inorganic Superabsorbent Hydrogels Based on Xylan and Montmorillonite

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Shuang Zhang ◽  
Ying Guan ◽  
Gen-Que Fu ◽  
Bo-Yang Chen ◽  
Feng Peng ◽  
...  
Keyword(s):  
Compressive Modulus ◽  
Cross Linking ◽  
Swelling Properties ◽  
Ph Values ◽  
Swelling Capacity ◽  
Wide Ph Range ◽  
Grafting Copolymerization ◽  
Ph Range ◽  
Influence Of Ph ◽  
Superabsorbent Hydrogels

The unique organic/inorganic superabsorbent hydrogels based on xylan and inorganic clay montmorillonite (MMT) were prepared via grafting copolymerization of acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) withN,N-methylenebisacrylamide (MBA) as a cross-linking agent and potassium persulfate (KPS) as an initiator. The effect of variables on the swelling capacity of the hydrogels, such as the weight ratios of MMT/xylan, MBA/xylan, and AMPS/AA, was systematically optimized. The results indicated that the superabsorbent hydrogels comprised a porous cross-linking structure of MMT and xylan with side chains that carry carboxylate, carboxamide, and sulfate. The hydrogels exhibit the high compressive modulus (E), about 35–55 KPa, and the compression strength of the hydrogels increased with an increment of the MMT content. The effect of various cationic salt solutions (LiCl, CaCl2, and FeCl3) on the swelling has the following order: Li+> Ca2+> Fe3+. Furthermore, the influence of pH values on swelling behaviors showed that the superabsorbent composites retained around 1000 g g−1over a wide pH range of 6.0–10.0. The xylan-based hydrogels with the high mechanical and swelling properties are promising for the applications in the biomaterials area.

Influence of pH on the Absorption and Fluorescence Spectra of 6,7-Dihydroxycoumarin in Aqueous Solution

1982 ◽  
Vol 37 (3) ◽  
pp. 262-265 ◽  
Author(s):  
Jerzy Grzywacz ◽  
Stanisława Taszner
Keyword(s):  
Aqueous Solution ◽  
Fluorescence Spectra ◽  
Singlet State ◽  
Ph Value ◽  
Emission Spectra ◽  
Excited Singlet ◽  
Acid Base ◽  
Wide Ph Range ◽  
Ph Range ◽  
Influence Of Ph

Abstract Absorption and emission spectra of 6,7-dihydroxycoumarin [6,7-DHC] in aqueous solution over a wide pH range are reported. The absorption spectra proved to be strongly sensitive to the pH-value of the solution, whereas the emission spectra change in this range only insignificantly. An interpretation is attempted on the basis of the differences of the acid-base properties of the 6,7-DHC molecule in its ground and excited singlet state. For this purpose the pKa's and pKax's values have been calculated. It has been stated that in the excited state the phototautomer form is very unlikely.

Influence of environmental factors on the growth and survival of Phytophthora clandestina

1986 ◽  
Vol 32 (7) ◽  
pp. 553-556 ◽  
Author(s):  
D. H. Wong ◽  
K. Sivasithamparam ◽  
M. J. Barbetti
Keyword(s):  
Water Potential ◽  
Lima Bean ◽  
Maximum Growth ◽  
Soil Conditions ◽  
Growth And Survival ◽  
Osmotic Water ◽  
Wide Ph Range ◽  
Ph Range ◽  
Initial Medium ◽  
Incubation Temperatures

The effects of temperature, pH, and osmotic water potential on the growth on lima bean agar and survival in soil of Phytophthora clandestina were investigated. On agar it grew over a wide pH range of 4–9 and growth increased as the pH of the initial medium rose from 4 to 6 at temperatures of 15, 20, and 25 °C. Growth was reduced by 58, 56, and 65% under acidic (pH 4) or by 54, 63, and 32% under alkaline (pH 9) conditions when compared with growth at pH 6 at 15, 20, and 25 °C, respectively. At 10, 15, 20, and 25 °C growth was reduced with increasing water stress. Generally growth increased with progressively increasing incubation temperatures up to 20 °C. Osmotic water potential of less than −12bars (1 bar = 100 kPa) prevented mycelial growth of P. clandestina. Maximum growth occurred on lima bean agar (0 bar) without KCl amendment at all temperatures. Survival of the pathogen within pasteurized soil was increased under cooler conditions (5–10 °C) at all water potentials tested (−0.01, −0.026, and −0.063 bars). At higher temperatures (15–32 °C) P. clandestina survived better under wetter soil conditions.

Photocatalytic mineralisation of perchloroethylene using titanium dioxide

1995 ◽  
Vol 31 (9) ◽  
pp. 47-54 ◽  
Author(s):  
Hani Gupta ◽  
Shuzo Tanaka
Keyword(s):  
Titanium Dioxide ◽  
Lag Time ◽  
Order Reaction ◽  
Co2 Production ◽  
First Order ◽  
Tio2 Particles ◽  
Initial Ph ◽  
Wide Ph Range ◽  
Catalyst Dosage ◽  
Ph Range

The photocatalytic mineralisation of perchloroethylene (PCE) is demonstrated mainly in terms of CO2 formation to investigate the effects of various factors such as dissolved oxygen (DO), titanium dioxide semiconductor (TiO2) catalyst dosage, PCE concentration and pH on PCE photocatalysis. PCE was rapidly adsorbed onto the TiO2 particles followed by its gradual degradation, and CO2 production started after a short lag time that corresponded to the adsorption phase. The rate of CO2 formation increased with increasing DO, TiO2 dosage and PCE concentration. There was no significant effect of initial pH on the CO2 production rate over a wide pH range. The dependence of the CO2 formation on PCE concentration was found to obey the Langmuir-Hinshelwood model. No intermediates were detected during PCE degradation and PCE degradation followed a first-order reaction.

scholarly journals Enhanced removal of selenate from mining effluent by H2O2/HCl-pretreated zero-valent iron

2018 ◽  
Vol 78 (11) ◽  
pp. 2404-2413 ◽  
Author(s):  
Bing Wu ◽  
Huichao Jia ◽  
Zhe Yang ◽  
Chao Shan ◽  
Jingxia Weng ◽  
...  
Keyword(s):  
Passive Layer ◽  
Zero Valent Iron ◽  
Mining Effluent ◽  
Acid Washing ◽  
Initial Ph ◽  
Wide Ph Range ◽  
Adsorption Reduction ◽  
Ph Range ◽  
Co Precipitation ◽  
Direct Use

Abstract Direct use of zero-valent iron (ZVI) in reductive removal of selenate (Se(VI)) is inefficient due to the intrinsic passive layer of ZVI. Here we observed that ZVI pretreated with H2O2 (P-ZVI-O) performs much better in Se(VI) removal from a mining effluent than other three modes of ZVI alone, acid washing ZVI (P-ZVI-A), and simultaneous addition of H2O2 and ZVI (ZVI-O) as well. The P-ZVI-O exhibits exceptionally high Se(VI) removal at a low dosage, wide pH range, with Se dropping down from 93.5 mg/L to <0.4 μg/L after 7-h reaction. Interestingly, the initial pH (2–6) of the mining effluent exerted little influence on the final Se(VI) removal. H2O2/HCl pretreatment results in the formation of various reducing corrosion products (e.g. Fe3O4, FeO and Fe2+), which greatly favors the efficient Se(VI) removal. In addition, surface-bound Fe2+ ions participated in the reduction of Se(VI). Combined with the influence of Se valence as well as pH and Fe2+ (whether dissolved or surface bound), it is deduced that the P-ZVI-O mode induced efficient Se(VI) removal via the adsorption-reduction and/or co-precipitation. This study demonstrates that H2O2/HCl pretreatment of ZVI is a very promising option to enhance the efficiency of reductive removal of Se(VI) from real effluents.

scholarly journals Strong adsorption of phosphate by amorphous lanthanum carbonate nano-adsorbents

2021 ◽  
Vol 83 (7) ◽  
pp. 1605-1618
Author(s):  
Yifan Lu ◽  
Huawei Wu ◽  
Yan Xia ◽  
Mei Huang
Keyword(s):  
Lanthanum Carbonate ◽  
Batch Adsorption ◽  
Maximum Adsorption Capacity ◽  
Water Matrix ◽  
Wide Range ◽  
Initial Ph ◽  
Wide Ph Range ◽  
Equilibrium Data ◽  
Ph Range ◽  
P Removal

Abstract Phosphorus removal is a crucial aspect of controlling water pollution and eutrophication. In this study, the preparation of lanthanum carbonate (LC) nano-adsorbents for the efficient removal of phosphate (P) from water and wastewater was investigated. Results from XRD, SEM and Zeta potential analyses revealed that addition of magnesium ions and adjustment of the reaction temperature could control the morphology and microstructure of LC. Effects of initial pH, adsorbent dosage, contact time, and the water matrix on P adsorption were investigated. Batch adsorption experiments revealed that LC showed strong performance on P removal over a wide pH range (3.0 to 11.0). The kinetic data followed a pseudo-second-order model, and equilibrium data were well fitted by the Langmuir model with a maximum adsorption capacity of 112.9 mg P/g. Adsorption thermodynamics showed that the adsorption process was exothermic and spontaneous. Results of a monolayer model for single adsorption indicated that P could completely interact with two or more functional groups from the LC surface. In the presence of competing ions (F−, Cl−, SO42−, NO3−, and HCO3−), LC maintained high selectivity for phosphate. For a real effluent, the P concentration was efficiently reduced from 3.2 mg P/L to below 0.5 mg P/L at a dose of 0.5 g/L LC. All the results suggested that LC can serve as a promising adsorbent for P removal in a wide range of pH, and thus could meet the stricter discharge regulations from actual wastewater.

scholarly journals Application of MIL-53(Fe) metal-organic framework material in catalytic wet oxidation of phenol

2021 ◽  
Vol 10 (1) ◽  
pp. 28-32
Author(s):  
Danh Huynh Thanh ◽  
Nghi Nguyen Huu ◽  
Du Pham Dinh
Keyword(s):  
Metal Organic Framework ◽  
Phenol Oxidation ◽  
Oxidation Reactions ◽  
Catalytic Wet Oxidation ◽  
X Ray Diffraction ◽  
Initial Ph ◽  
Wide Ph Range ◽  
Metal Organic ◽  
Ph Range ◽  
Organic Framework

In the present study, MIL-53(Fe) metal-organic framework material was applied as catalyst for phenol oxidation reaction in aqueous solution with H2O2 under UV radiation. The materials were characterized using X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FT-IR). The effects of reaction time, initial phenol concentration, and initial pH of the solution on phenol oxidation reactions were investigated. The results indicated that MIL-53(Fe) could work effectively in the wide pH range from 2 to 10. Phenol was quickly oxidized to form simple organic acids, including acetic acid, formic acid and oxalic acid.

Removal of U(VI) from aqueous solution using phosphate functionalized bacterial cellulose as efficient adsorbent

2019 ◽  
Vol 107 (6) ◽  
pp. 459-467 ◽  
Author(s):  
Shuting Zhuang ◽  
Jianlong Wang
Keyword(s):  
Adsorption Capacity ◽  
Bacterial Cellulose ◽  
Maximum Adsorption Capacity ◽  
Order Kinetic ◽  
Initial Ph ◽  
Wide Ph Range ◽  
Order Kinetic Model ◽  
Pseudo Second Order ◽  
Ph Range ◽  
Efficient Adsorbent

Abstract In this study, phosphate functionalized bacterial cellulose with micro-fibrous structure was prepared, characterized and applied for U(VI) adsorption. The successful grafting of phosphoric functional groups was proved by the FTIR spectra and EDS analysis (P~4.15 wt%), and the porous structure was confirmed by SEM and BET analyses. Furthermore, the effect of initial pH, contact time, initial concentration, and temperature were studied. The as-prepared adsorbent showed a high adsorption capacity at wide pH range (4.0–8.0) and its maximum adsorption capacity was calculated to be 50.65 mg/g. This endothermic adsorption process conformed to the pseudo second-order kinetic model and the Elovich kinetic models and the Langmuir isothermal models. According to the FTIR and XPS analysis, an adsorption mechanism was tentatively proposed, mainly due to the interaction between U(VI) and phosphoric groups.

Role of Some Neosynthesized Styryl Heterocycles in Ochratoxin A Control in Aspergillus carbonarius

2016 ◽  
Vol 20 (19) ◽  
pp. 2029-2035 ◽  
Author(s):  
Roberto Antonioletti ◽  
Angela Viglianti ◽  
Stefano Cristofoli ◽  
Alessandra Ricelli
Keyword(s):  
Ochratoxin A ◽  
Aspergillus Carbonarius
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