scholarly journals Transglycosylation of Rebaudioside А by β-fructofuranosidase

2019 ◽  
Vol 1 (1) ◽  
pp. 103-112
Author(s):  
Kristina Chkhan
Keyword(s):  
Reaction Time ◽  
Total Concentration ◽  
Weight Ratio ◽  
Rebaudioside A ◽  
Concentrated Solutions ◽  
Organoleptic Evaluation ◽  
Isolation And Purification ◽  
Ph Values ◽  
Derivatives Of ◽  
Low Calorie Sweetener

Rebaudioside A (RebaA) was subjected to β-2.6 transglycosylation with β-fructofuranosidase from Arthrobacter sp. K-1 and sucrose as a source of fructose units. The yield of transglycosylation depends significantly on the concentration of the acceptor, the donor and the enzyme, as well as the reaction time. At the weight ratio of RebА to sucrose of 1: 1, the degree of transfructosylation in 24 hours was only 5.4%, while at a ratio of 1 : 5, it reaches to more than 23%. It was revealed that transfructosylation proceeds more efficiently in the concentrated solutions, the higher the total concentration of sucrose and RebaA, the greater the yield of fructosylated RebA. To determine the effect of рН on transfructosylation, β-fructofuranosidase was incubated with a solution of 1% RebА and 10% sucrose at 40°C for 15 hours at various pH values. It was also revealed that with an increase in the amount of the enzyme, the reaction accelerates. The most optimal were quantities of 50-100 units per 1 g of sucrose. The reaction of transfructosylation of stevioside is examined, and an organoleptic evaluation of fructosylated derivatives of fructosyl-RebА, fructosyl-stevioside and fructosyl-rubuzoside is also shown. Isolation and purification of fructosylated Reba was carried out by ethanol precipitation and purification on the columns filled with macroporous Diaion HP-20 resin. The resulting product is possessing improved sensory characteristics and can be used as low-calorie sweetener.

Derivatives of isatin in aqueous solution. I. Kinetics of ring opening of Isatin-5-sulfonate

1981 ◽  
Vol 34 (2) ◽  
pp. 365 ◽  
Author(s):  
H Stunzi
Keyword(s):  
Ring Opening ◽  
Rate Of Change ◽  
Spectroscopic Methods ◽  
Ph Values ◽  
Buffer Region ◽  
Pka Value ◽  
Back Titration ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Sulfonate Anion

The reactions of isatin-5-sulfonate anion (si-) which cause a hysteresis in pH titrations were studied by pH-metric and n.m.r, spectroscopic methods. Rapid alkalimetric titrations [I 0.15 M (KNO3),37�] gave the pKa value corresponding to the addition of OH- to si- [pKa(ring) 9.55]. The slow ring opening to the sulfonatoisatate dianion (sia2-) led to a drift of the pH values towards an equilibrium buffer region. Its pKa, value [pKa(eq) 3.44] corresponds to the reaction si-+H2O ↔ sia 2-+H+ Rapid back-titration gave the pKa value of the ring-opened species Hsia- [pKa(open) c. 1.3]. The rate law for the ring opening d[sia]/dt=k2 [siOH](OH)+k1*[si] was obtained from the rate of change of pH. N-Methylisatin-5-sulfonate behaves analogously.

scholarly journals Sulfamethoxazole and Trimethoprim Degradation by Fenton and Fenton-Like Processes

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1655 ◽  
Author(s):  
Antover Panazzolo Sarmento ◽  
Alisson Carraro Borges ◽  
Antonio Teixeira de Matos ◽  
Lincoln Lucílio Romualdo
Keyword(s):  
Reaction Time ◽  
Fenton Reaction ◽  
Desirability Function ◽  
Relative Concentration ◽  
Optimum Conditions ◽  
Degradation Model ◽  
Pareto Chart ◽  
Linear Effect ◽  
Ph Values ◽  
Antibiotic Degradation

In this work, the degradation of sulfamethoxazole (SMX) and trimethoprim (TMP) via Fenton and Fenton-like processes was evaluated using Mn2+ as supporting catalyst in the Fenton reaction. The optimum conditions of degradation were also evaluated. Besides that, the effect of independent factors pH, [H2O2], [Fe2+], [Mn2+] and reaction time (t) on the efficiency of the SMX and TMP degradation were assessed. Box–Behnken was the experimental design adopted, delineating the relative concentration (C/Co) of antibiotics after treatments as response variable. The inferences were conducted using variance analysis, Pareto chart, response surface methodology, and desirability function. Due to the lack of adjustment of the SMX degradation model, there are no more inferences about it. The significant variables (p ≤ 0.05) on TMP degradation were: reaction time quadratic and linear effect, [Fe2+] linear effect, [Mn2+] linear effect, interaction pH vs. [Mn2+]. The Mn2+ addition aided TMP degradation in environments with lower pH values. However, the addition may harm the efficiency of the antibiotic degradation at higher pH. The optimum condition for TMP degradation in the conventional process (without the addition of Mn2+) is: pH 5, [H2O2] equal to 4.41 mmol L−1, [Fe2+] equal to 0.81 mmol L−1 and 90 min reaction time.

Preliminary Study on the Removal of Hexavalent Chromium in Wastewater with Reduction of Sulfur Dioxide

2013 ◽  
Vol 864-867 ◽  
pp. 1699-1703
Author(s):  
Ji Ming Wu ◽  
Sheng Gao Cheng
Keyword(s):  
Reaction Time ◽  
Sulfur Dioxide ◽  
Hexavalent Chromium ◽  
Reduction Reaction ◽  
High Concentration ◽  
Reaction Conditions ◽  
Ph Values ◽  
Different Temperatures ◽  
Preliminary Study ◽  
High Concentrations

The paper focused on a self-developed methodology through using sulfur dioxide to deal with high concentration of chromium-containing wastewater. It studied the effects of different pH values, different reaction time, different temperatures and different amounts of sulfur with sulfur dioxide reduction reaction on the chromium-containing wastewater. The results showed that: when the reaction conditions were controlled as follows: the pH values ranged from 2 to 4, the reaction temperature was controlled 40~60°C, the amount of sulfur in theoretical was 1.2 times and the reaction time was 40 min, the hexavalent chromium in the high concentrations of chromium-containing wastewater could be effectively removed.

Study on the Hydrolysis of Pollen in Pure Water under Microwave Irradiation

2013 ◽  
Vol 683 ◽  
pp. 222-225
Author(s):  
Huan Wang ◽  
Li Li Geng ◽  
Bo Wu ◽  
Na Liu ◽  
Dong Zhang
Keyword(s):  
Reaction Time ◽  
Microwave Irradiation ◽  
Microwave Power ◽  
Orthogonal Experiment ◽  
Pure Water ◽  
Influence Factors ◽  
Weight Ratio ◽  
Pinus Massoniana ◽  
Hydrolysis Reaction ◽  
Microwave Hydrolysis

Pinus massoniana pollen was hydrolyzed by using the method of orthogonal experiment in pure water under microwave irradiation. The main influence factors of pollen microwave hydrolysis reaction was confirmed as temperature, weight ratio of pollen to water, microwave power and the reaction time, and its effects on the pollen microwave hydrolysis reaction was studied in detail. The results showed that the sequence of influence factors was reaction temperature>weight ratio of pollen to water>microwave power>reaction time. The optimal reaction conditions was that the temperature, 120oC; the power, 120W; the reaction time, 150min; the weight ratio of pollen to water, 1:10.

scholarly journals Biodiesel Production using Synthesized HY Zeolite Catalyst

2021 ◽  
Vol 11 (3) ◽  
pp. 1-18
Author(s):  
Dr. Ban A. Al-Tabbakh ◽  
Sattar J. Hussein ◽  
Zena A. Hadi
Keyword(s):  
Oleic Acid ◽  
Reaction Time ◽  
Sunflower Oil ◽  
Zeolite Catalyst ◽  
Weight Ratio ◽  
Biodiesel Production ◽  
Molar Ratio ◽  
Hy Zeolite ◽  
Factors Affecting ◽  
Acid Esterification

Biodiesel was produced using oleic acid esterification and transesterification of the sunflower oil methods. Many different factors affecting production procedures were studied such as reaction temperature, the molar ratio of ethanol to oil, reaction time and concentration of HY catalyst. Different techniques such as TGA, FTIR and Mass spectroscopy were used to syntheses biodiesel. Results showed that 78% of oleic acid maximum conversion was obtained at a temperature of 70oC with molar ratio 12:1 ethanol: oil with 5 wt.% catalysts at 90 min reaction time, while for sunflower oil conversion of 98% at 200oC with 5 weight ratio of ethanol: oil at a time of 3 h was successfully obtained.

Accessibility of Tyrosine Residues in Cytochrome P-450scc (CYP11A1)

1998 ◽  
Vol 63 (10) ◽  
pp. 1678-1682
Author(s):  
Pavel Anzenbacher ◽  
Jiří Hudeček ◽  
Reinhard Lange ◽  
Frédéric Bancel
Keyword(s):  
Absorption Spectra ◽  
Conformational Equilibrium ◽  
Ultraviolet Region ◽  
Conformational States ◽  
Compact Structure ◽  
Tyrosine Residues ◽  
Temperature Range ◽  
Ph Values ◽  
Derivatives Of

Cytochrome P-450scc (CYP11A1) is known to exist in various conformational states. To study the accessibility of tyrosine residues to the solvent, second and fourth derivatives of cytochrome absorption spectra in the ultraviolet region were used. The measurements were carried out in the temperature range -10 to 40 °C and at two pH values (6.8 and 7.4). Our results indicate that the tyrosine residues of this enzyme are less accessible at higher temperatures as well as at higher pH, that is at conditions where the conformational equilibrium shifts to low-spin Fe(III) form(s). In other words, a more compact structure is attributable to the low-spin Fe(III) form(s) of P-450scc.

scholarly journals Impacts of Nickel Nanoparticles on Mineral Carbonation

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Marius Bodor ◽  
Rafael M. Santos ◽  
Yi Wai Chiang ◽  
Maria Vlad ◽  
Tom Van Gerven
Keyword(s):  
Reaction Time ◽  
Nickel Nanoparticles ◽  
Carbonic Acid ◽  
Mineral Carbonation ◽  
Ph Values ◽  
Bicarbonate Ions ◽  
Steelmaking Slags ◽  
Initial Stage ◽  
Solids Content ◽  
Rate Limiting

This work presents experimental results regarding the use of pure nickel nanoparticles (NiNP) as a mineral carbonation additive. The aim was to confirm if the catalytic effect of NiNP, which has been reported to increase the dissolution of CO2and the dissociation of carbonic acid in water, is capable of accelerating mineral carbonation processes. The impacts of NiNP on the CO2mineralization by four alkaline materials (pure CaO and MgO, and AOD and CC steelmaking slags), on the product mineralogy, on the particle size distribution, and on the morphology of resulting materials were investigated. NiNP-containing solution was found to reach more acidic pH values upon CO2bubbling, confirming a higher quantity of bicarbonate ions. This effect resulted in acceleration of mineral carbonation in the first fifteen minutes of reaction time when NiNP was present. After this initial stage, however, no benefit of NiNP addition was seen, resulting in very similar carbonation extents after one hour of reaction time. It was also found that increasing solids content decreased the benefit of NiNP, even in the early stages. These results suggest that NiNP has little contribution to mineral carbonation processes when the dissolution of alkaline earth metals is rate limiting.

scholarly journals Studies on the preparation of water-insoluble derivatives of rennin and chymotrypsin and their use in the hydrolysis of casein and the clotting of milk

1969 ◽  
Vol 115 (2) ◽  
pp. 183-190 ◽  
Author(s):  
Margaret L. Green ◽  
G. Crutchfield
Keyword(s):  
Continuous System ◽  
Competitive Inhibitor ◽  
Active Enzyme ◽  
Ph Values ◽  
Hydrolysis Of ◽  
Derivatives Of

1. Enzymically active insoluble derivatives of chymotrypsin and rennin were prepared by coupling each enzyme to agarose as described by Porath, Axén & Ernback (1967) and rennin to aminoethylcellulose by the method of Habeeb (1967). 2. Agarose–chymotrypsin was stable over the range pH2–9, but agarose–rennin released active enzyme into solution at above pH2 and aminoethylcellulose–rennin was similarly unstable at certain pH values. 3. Each derivative appeared to catalyse the clotting of milk at 30°, but this was probably entirely due to enzyme released into solution from the carrier. 4. The presence of a competitive inhibitor of chymotrypsin during its coupling to agarose had no effect on the activity or stability of the resulting derivative. 5. The characteristics of agarose and cellulose render them not entirely suitable for use in a continuous system with milk.

Deacification of High Acid-Containing Crude by Solvent Extraction under Ultrasonic Irradiation

2014 ◽  
Vol 521 ◽  
pp. 638-643
Author(s):  
Hong Guan Wu ◽  
Hai Feng Li ◽  
Guo Xian Yu
Keyword(s):  
Reaction Time ◽  
Solvent Extraction ◽  
Ethylene Glycol ◽  
Ultrasonic Irradiation ◽  
Weight Ratio ◽  
Acid Value ◽  
Naphthenic Acids ◽  
Extraction Solvent ◽  
Glycol Solution ◽  
Temperature Time

A compounded deacidificant was used for deacidification of domestic Bei-Jiang crude. In this work, its formulation was optimized in detail. Effect of reaction temperature, time and the ratio to crude oil was examined. Acceleration by using ultrasonic irritation in deacidification process was investigated. Our results revealed a deacificant composed of ethylene glycol as neutralization agent and cyclohexylamine as extraction solvent not only provided an excellent deacidificcation extent, but also no emulsion problem appeared. 30% cyclohexylamine-containing ethylene glycol solution has the best performance. Deacidification extent reached 85% and higher at a solvent and oil weight ratio of 15%.Ultrasonic wave played an accerleration role, resulting in a shorter reaction time. Naphthenic acids and solvent components were recovered by using vacuum distillation.The recovery rate for solvent components were 99.3% for ethylene and 96.6% for cyclohexylamine respectively. The purity of recovered naphthenic acids was rather high, reaching a acid value of 167.

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