The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Gary M. Mcdonald - One of the best experts on this subject based on the ideXlab platform.
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acid catalyzed partial Hydrolysis of carbohydrate groups of the potato glycoalkaloid alpha chaconine in alcoholic solutions
Journal of Agricultural and Food Chemistry, 1995Co-Authors: Mendel Friedman, Gary M. McdonaldAbstract:As part of an effort to improve the safety of plant-derived foods, the role of the carbohydrate side chain has been explored in biological effects of potato glycoalkaloids such as α-chaconine. This steroid glycoalkaloid has a trisaccharide attached to the 3-hydroxy position of the steroidal aglycon solanidine. This study attempts to define the effect of structurally different alcohols on the partial Hydrolysis of α-chaconine to β 1 -chaconine, β 2 -chaconine, γ-chaconine, and solanidine. Partial hydrolyses were carried out in 97.5% alcohol-0.25 N HCl at 60 °C. HPLC was used to measure the distribution of Hydrolysis products as a function of time. The rate of Hydrolysis of α-chaconine in the straight-chain alcohol solutions was as follows : methanol > ethanol = 1-butanol > propanol > pentanol » water. The longer the chain, the slower the rate of Hydrolysis except for the anomalous result that the extent of Hydrolysis in 1-butanol was equal to that in ethanol. However, Hydrolysis in 2-butanol was slower than in 1-butanol. Surprisingly, Hydrolysis in tert-butyl alcohol was slowest, proceeding more slowly than even in 1-pentanol. The formation of γ-chaconine was also greatly reduced in tert-butyl alcohol. Mechanistic rationalizations are offered to explain the observed trends in terms of the hydrophobic-hydrophilic nature of the glycoalkaloids and the solvation properties of the alcohols. The results should be generally useful for optimizing or minimizing the formation of specific Hydrolysis products.
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kinetics of acid catalyzed Hydrolysis of carbohydrate groups of potato glycoalkaloids alpha chaconine and alpha solanine
Journal of Agricultural and Food Chemistry, 1993Co-Authors: Mendel Friedman, Gary M. Mcdonald, William F HaddonAbstract:As part of a broader plan designed to characterize Solanum glycoalkaloids and their Hydrolysis products and biosynthetic intermediates, to identify plant enzymes in the biosynthetic pathways, and to develop a relative toxicity scale for glycoalkaloids, we examined conditions that favor the Hydrolysis of carbohydrate portions of α-chaconine and α-solanine. These two triglycosides can each form two diglycosides, one monoglycoside, the so-called β 1 -, β 2 -, and γ-chaconines and -solanines, and a common aglycon, solanidine. An incomplete Hydrolysis mixture should therefore contain nine compounds. Hydrolyses were carried out in 0.1, 0.2, and 0.5 N HCl-methanol at 38, 55, and 65 o C for various time periods
Mendel Friedman - One of the best experts on this subject based on the ideXlab platform.
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acid catalyzed partial Hydrolysis of carbohydrate groups of the potato glycoalkaloid alpha chaconine in alcoholic solutions
Journal of Agricultural and Food Chemistry, 1995Co-Authors: Mendel Friedman, Gary M. McdonaldAbstract:As part of an effort to improve the safety of plant-derived foods, the role of the carbohydrate side chain has been explored in biological effects of potato glycoalkaloids such as α-chaconine. This steroid glycoalkaloid has a trisaccharide attached to the 3-hydroxy position of the steroidal aglycon solanidine. This study attempts to define the effect of structurally different alcohols on the partial Hydrolysis of α-chaconine to β 1 -chaconine, β 2 -chaconine, γ-chaconine, and solanidine. Partial hydrolyses were carried out in 97.5% alcohol-0.25 N HCl at 60 °C. HPLC was used to measure the distribution of Hydrolysis products as a function of time. The rate of Hydrolysis of α-chaconine in the straight-chain alcohol solutions was as follows : methanol > ethanol = 1-butanol > propanol > pentanol » water. The longer the chain, the slower the rate of Hydrolysis except for the anomalous result that the extent of Hydrolysis in 1-butanol was equal to that in ethanol. However, Hydrolysis in 2-butanol was slower than in 1-butanol. Surprisingly, Hydrolysis in tert-butyl alcohol was slowest, proceeding more slowly than even in 1-pentanol. The formation of γ-chaconine was also greatly reduced in tert-butyl alcohol. Mechanistic rationalizations are offered to explain the observed trends in terms of the hydrophobic-hydrophilic nature of the glycoalkaloids and the solvation properties of the alcohols. The results should be generally useful for optimizing or minimizing the formation of specific Hydrolysis products.
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kinetics of acid catalyzed Hydrolysis of carbohydrate groups of potato glycoalkaloids alpha chaconine and alpha solanine
Journal of Agricultural and Food Chemistry, 1993Co-Authors: Mendel Friedman, Gary M. Mcdonald, William F HaddonAbstract:As part of a broader plan designed to characterize Solanum glycoalkaloids and their Hydrolysis products and biosynthetic intermediates, to identify plant enzymes in the biosynthetic pathways, and to develop a relative toxicity scale for glycoalkaloids, we examined conditions that favor the Hydrolysis of carbohydrate portions of α-chaconine and α-solanine. These two triglycosides can each form two diglycosides, one monoglycoside, the so-called β 1 -, β 2 -, and γ-chaconines and -solanines, and a common aglycon, solanidine. An incomplete Hydrolysis mixture should therefore contain nine compounds. Hydrolyses were carried out in 0.1, 0.2, and 0.5 N HCl-methanol at 38, 55, and 65 o C for various time periods
William F Haddon - One of the best experts on this subject based on the ideXlab platform.
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kinetics of acid catalyzed Hydrolysis of carbohydrate groups of potato glycoalkaloids alpha chaconine and alpha solanine
Journal of Agricultural and Food Chemistry, 1993Co-Authors: Mendel Friedman, Gary M. Mcdonald, William F HaddonAbstract:As part of a broader plan designed to characterize Solanum glycoalkaloids and their Hydrolysis products and biosynthetic intermediates, to identify plant enzymes in the biosynthetic pathways, and to develop a relative toxicity scale for glycoalkaloids, we examined conditions that favor the Hydrolysis of carbohydrate portions of α-chaconine and α-solanine. These two triglycosides can each form two diglycosides, one monoglycoside, the so-called β 1 -, β 2 -, and γ-chaconines and -solanines, and a common aglycon, solanidine. An incomplete Hydrolysis mixture should therefore contain nine compounds. Hydrolyses were carried out in 0.1, 0.2, and 0.5 N HCl-methanol at 38, 55, and 65 o C for various time periods
Keikhosro Karimi - One of the best experts on this subject based on the ideXlab platform.
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Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: A review
International Journal of Molecular Sciences, 2008Co-Authors: Mohammad J. Taherzadeh, Keikhosro KarimiAbstract:Lignocelluloses are often a major or sometimes the sole components of different waste streams from various industries, forestry, agriculture and municipalities. Hydrolysis of these materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. However, enzymatic Hydrolysis of lignocelluloses with no pretreatment is usually not so effective because of high stability of the materials to enzymatic or bacterial attacks. The present work is dedicated to reviewing the methods that have been studied for pretreatment of lignocellulosic wastes for conversion to ethanol or biogas. Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first. Then, several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described. They include milling, irradiation, microwave, steam explosion, ammonia fiber explosion (AFEX), supercritical CO(2) and its explosion, alkaline Hydrolysis, liquid hot-water pretreatment, organosolv processes, wet oxidation, ozonolysis, dilute-and concentrated-acid hydrolyses, and biological pretreatments.
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conversion of rice straw to sugars by dilute acid Hydrolysis
Biomass & Bioenergy, 2006Co-Authors: Keikhosro Karimi, Shauker Kheradmandinia, Mohammad J. TaherzadehAbstract:Abstract Hydrolysis of rice straw by dilute sulfuric acid at high temperature and pressure was investigated in one and two stages. The hydrolyses were carried out in a 10-l reactor, where the Hydrolysis retention time (3–10 min), pressure (10–35 bar) and acid concentration (0–1%) were examined. Optimization of first stage Hydrolysis is desirable to achieve the highest yield of the sugars from hemicellulose and also as a pretreatment for enzymatic Hydrolysis. The results show the ability of first stage Hydrolysis to depolymerize xylan to xylose with a maximum yield of 80.8% at Hydrolysis pressure of 15 bar, 10 min retention time and 0.5% acid concentration. However, the yield of glucose from glucan was relatively low in first stage Hydrolysis at a maximum of 25.8%. The solid residuals were subjected to further dilute-acid Hydrolysis in this study. This second-stage Hydrolysis without addition of the acid could not increase the yield of glucose from glucan beyond 26.6%. On the other hand, the best results of the Hydrolysis were achieved, when 0.5% sulfuric acid was added prior to each stage in two-stage Hydrolysis. The best results of the second stage of the Hydrolysis were achieved at the Hydrolysis pressure and the retention time of 30 bar and 3 min in the second stage Hydrolysis, where a total of 78.9% of xylan and 46.6% of glucan were converted to xylose and glucose, respectively in the two stages. Formation of furfural and HMF were functions of the Hydrolysis pressure, acid concentration, and retention time, whereas the concentration of acetic acid was almost constant at pressure of higher than 10 bar and a total retention time of 10 min.
Mohammad J. Taherzadeh - One of the best experts on this subject based on the ideXlab platform.
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Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: A review
International Journal of Molecular Sciences, 2008Co-Authors: Mohammad J. Taherzadeh, Keikhosro KarimiAbstract:Lignocelluloses are often a major or sometimes the sole components of different waste streams from various industries, forestry, agriculture and municipalities. Hydrolysis of these materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. However, enzymatic Hydrolysis of lignocelluloses with no pretreatment is usually not so effective because of high stability of the materials to enzymatic or bacterial attacks. The present work is dedicated to reviewing the methods that have been studied for pretreatment of lignocellulosic wastes for conversion to ethanol or biogas. Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first. Then, several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described. They include milling, irradiation, microwave, steam explosion, ammonia fiber explosion (AFEX), supercritical CO(2) and its explosion, alkaline Hydrolysis, liquid hot-water pretreatment, organosolv processes, wet oxidation, ozonolysis, dilute-and concentrated-acid hydrolyses, and biological pretreatments.
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conversion of rice straw to sugars by dilute acid Hydrolysis
Biomass & Bioenergy, 2006Co-Authors: Keikhosro Karimi, Shauker Kheradmandinia, Mohammad J. TaherzadehAbstract:Abstract Hydrolysis of rice straw by dilute sulfuric acid at high temperature and pressure was investigated in one and two stages. The hydrolyses were carried out in a 10-l reactor, where the Hydrolysis retention time (3–10 min), pressure (10–35 bar) and acid concentration (0–1%) were examined. Optimization of first stage Hydrolysis is desirable to achieve the highest yield of the sugars from hemicellulose and also as a pretreatment for enzymatic Hydrolysis. The results show the ability of first stage Hydrolysis to depolymerize xylan to xylose with a maximum yield of 80.8% at Hydrolysis pressure of 15 bar, 10 min retention time and 0.5% acid concentration. However, the yield of glucose from glucan was relatively low in first stage Hydrolysis at a maximum of 25.8%. The solid residuals were subjected to further dilute-acid Hydrolysis in this study. This second-stage Hydrolysis without addition of the acid could not increase the yield of glucose from glucan beyond 26.6%. On the other hand, the best results of the Hydrolysis were achieved, when 0.5% sulfuric acid was added prior to each stage in two-stage Hydrolysis. The best results of the second stage of the Hydrolysis were achieved at the Hydrolysis pressure and the retention time of 30 bar and 3 min in the second stage Hydrolysis, where a total of 78.9% of xylan and 46.6% of glucan were converted to xylose and glucose, respectively in the two stages. Formation of furfural and HMF were functions of the Hydrolysis pressure, acid concentration, and retention time, whereas the concentration of acetic acid was almost constant at pressure of higher than 10 bar and a total retention time of 10 min.
