The Experts below are selected from a list of 21321 Experts worldwide ranked by ideXlab platform
Thomas W. Jeffries - One of the best experts on this subject based on the ideXlab platform.
-
the roles of xylan and lignin in Oxalic Acid pretreated corncob during separate enzymatic hydrolysis and ethanol fermentation
Bioresource Technology, 2010Co-Authors: Rita C L B Rodrigues, Ingyu Choi, Thomas W. JeffriesAbstract:Abstract High yields of hemicellulosic and cellulosic sugars are critical in obtaining economical conversion of agricultural residues to ethanol. To optimize pretreatment conditions, we evaluated Oxalic Acid loading rates, treatment temperatures and times in a 23 full factorial design. Response-surface analysis revealed an optimal Oxalic Acid pretreatment condition to release sugar from the cob of Zea mays L. ssp. and for Pichia stipitis CBS 6054. To ferment the residual cellulosic sugars to ethanol following enzymatic hydrolysis, highest saccharification and fermentation yields were obtained following pretreatment at 180 °C for 50 min with 0.024 g Oxalic Acid/g substrate. Under these conditions, only 7.5% hemicellulose remained in the pretreated substrate. The rate of cellulose degradation was significantly less than that of hemicellulose and its hydrolysis was not as extensive. Subsequent enzymatic saccharification of the residual cellulose was strongly affected by the pretreatment condition with cellulose hydrolysis ranging between 26.0% and 76.2%. The residual xylan/lignin ratio ranged from 0.31 to 1.85 depending on the pretreatment condition. Fermentable sugar and ethanol were maximal at the lowest ratio of xylan/lignin and at high glucan contents. The model predicts optimal condition of Oxalic Acid pretreatment at 168 °C, 74 min and 0.027 g/g of Oxalic Acid. From these findings, we surmised that low residual xylan was critical in obtaining maximal glucose yields from saccharification.
-
simultaneous saccharification and ethanol fermentation of Oxalic Acid pretreated corncob assessed with response surface methodology
Bioresource Technology, 2009Co-Authors: Rita C L B Rodrigues, Thomas W. JeffriesAbstract:Response surface methodology was used to evaluate optimal time, temperature and Oxalic Acid concentration for simultaneous saccharification and fermentation (SSF) of corncob particles by Pichia stipitis CBS 6054. Fifteen different conditions for pretreatment were examined in a 2 3 full factorial design with six axial points. Temperatures ranged from 132 to 180 C, time from 10 to 90 min and Oxalic Acid loadings from 0.01 to 0.038 g/g solids. Separate maxima were found for enzymatic saccharification and hemicellulose fermentation, respectively, with the condition for maximum saccharification being significantly more severe. Ethanol production was affected by reaction temperature more than by Oxalic Acid and reaction time over the ranges examined. The effect of reaction temperature was significant at a 95% confidence level in its effect on ethanol production. Oxalic Acid and reaction time were statistically significant at the 90% level. The highest ethanol concentration (20 g/l) was obtained after 48 h with an ethanol volumetric production rate of 0.42 g ethanol l � 1 h � 1 . The ethanol yield after SSF with P. stipitis was significantly higher than predicted by sequential saccharification and fermentation of substrate pretreated under the same condition. This was attributed to the secretion of b-glucosidase by P. stipitis. During SSF, free extracellular b-glucosidase activity was 1.30 pNPG U/g with P. stipitis, while saccharification without the yeast was 0.66 pNPG U/g. Published by Elsevier Ltd.
-
simultaneous saccharification and ethanol fermentation of Oxalic Acid pretreated corncob assessed with response surface methodology
Bioresource Technology, 2009Co-Authors: Rita C L B Rodrigues, Thomas W. JeffriesAbstract:Response surface methodology was used to evaluate optimal time, temperature and Oxalic Acid concentration for simultaneous saccharification and fermentation (SSF) of corncob particles by Pichia stipitis CBS 6054. Fifteen different conditions for pretreatment were examined in a 2 3 full factorial design with six axial points. Temperatures ranged from 132 to 180 C, time from 10 to 90 min and Oxalic Acid loadings from 0.01 to 0.038 g/g solids. Separate maxima were found for enzymatic saccharification and hemicellulose fermentation, respectively, with the condition for maximum saccharification being significantly more severe. Ethanol production was affected by reaction temperature more than by Oxalic Acid and reaction time over the ranges examined. The effect of reaction temperature was significant at a 95% confidence level in its effect on ethanol production. Oxalic Acid and reaction time were statistically significant at the 90% level. The highest ethanol concentration (20 g/l) was obtained after 48 h with an ethanol volumetric production rate of 0.42 g ethanol l � 1 h � 1 . The ethanol yield after SSF with P. stipitis was significantly higher than predicted by sequential saccharification and fermentation of substrate pretreated under the same condition. This was attributed to the secretion of b-glucosidase by P. stipitis. During SSF, free extracellular b-glucosidase activity was 1.30 pNPG U/g with P. stipitis, while saccharification without the yeast was 0.66 pNPG U/g. Published by Elsevier Ltd.
-
effect of Oxalic Acid pretreatment on yellow poplar liriodendron tulipifera for ethanol production
Journal of the Korean wood science and technology, 2009Co-Authors: Kim Hyeyun, Thomas W. Jeffries, J W Lee, Gwak Kiseob, Choi IngyuAbstract:In this study, we investigated the potential of producing bioethanol from Liriodendron tulipifera by using Oxalic Acid pretreatment. Amounts of fermentable sugars, mostly xylose and glucose, in the liquid fraction (hydrolysate) was 40.22 g/ after the biomass was pretreated with 0.037 g/g of Oxalic Acid for 20 minutes at 160. Production amounts of ethanol was 8.6 g/ from the 72 hours of simultaneous saccharification and fermentation (SSF) on solid fraction of the pretreated sample. At the same condition, when the reaction time increased to 40 minutes, 32.66 g/ of fermentable sugars in the hydrolysate and 9.5 g/ of ethanol was produced from the process of pretreatment and SSF. As a result of analyzing the fermentation inhibitors, such as acetic Acid, 5-HMF, furfural and total phenolic compounds, as the reaction time increased, the amount of the fermentation inhibitors in the hydrolysate increased. Production of the fermentation inhibitors was more affected by initial concentration of Oxalic Acid rather than reaction time. 3.395.78 g/ of acetic Acid was produced by pretreatment with 0.013 g/g of Oxalic Acid, and the amount of furfural produced by decomposition of xylose was 23 times higher than the amount of 5-HMF produced by decomposition of glucose. All the hydrolysates contained more than 5 g/ of total phenols considered as the degradation product of lignin. Therefore, by analyzing the amount of fermentable sugars and fermentation inhibitors in the hydrolysate, and producing ethanol from SSF of solid fraction of the pretreated sample, the biomass pretreated with 0.037 g/g of Oxalic Acid for 20 minutes at 160 can be expected to produce the most ethanol.
Rita C L B Rodrigues - One of the best experts on this subject based on the ideXlab platform.
-
the roles of xylan and lignin in Oxalic Acid pretreated corncob during separate enzymatic hydrolysis and ethanol fermentation
Bioresource Technology, 2010Co-Authors: Rita C L B Rodrigues, Ingyu Choi, Thomas W. JeffriesAbstract:Abstract High yields of hemicellulosic and cellulosic sugars are critical in obtaining economical conversion of agricultural residues to ethanol. To optimize pretreatment conditions, we evaluated Oxalic Acid loading rates, treatment temperatures and times in a 23 full factorial design. Response-surface analysis revealed an optimal Oxalic Acid pretreatment condition to release sugar from the cob of Zea mays L. ssp. and for Pichia stipitis CBS 6054. To ferment the residual cellulosic sugars to ethanol following enzymatic hydrolysis, highest saccharification and fermentation yields were obtained following pretreatment at 180 °C for 50 min with 0.024 g Oxalic Acid/g substrate. Under these conditions, only 7.5% hemicellulose remained in the pretreated substrate. The rate of cellulose degradation was significantly less than that of hemicellulose and its hydrolysis was not as extensive. Subsequent enzymatic saccharification of the residual cellulose was strongly affected by the pretreatment condition with cellulose hydrolysis ranging between 26.0% and 76.2%. The residual xylan/lignin ratio ranged from 0.31 to 1.85 depending on the pretreatment condition. Fermentable sugar and ethanol were maximal at the lowest ratio of xylan/lignin and at high glucan contents. The model predicts optimal condition of Oxalic Acid pretreatment at 168 °C, 74 min and 0.027 g/g of Oxalic Acid. From these findings, we surmised that low residual xylan was critical in obtaining maximal glucose yields from saccharification.
-
simultaneous saccharification and ethanol fermentation of Oxalic Acid pretreated corncob assessed with response surface methodology
Bioresource Technology, 2009Co-Authors: Rita C L B Rodrigues, Thomas W. JeffriesAbstract:Response surface methodology was used to evaluate optimal time, temperature and Oxalic Acid concentration for simultaneous saccharification and fermentation (SSF) of corncob particles by Pichia stipitis CBS 6054. Fifteen different conditions for pretreatment were examined in a 2 3 full factorial design with six axial points. Temperatures ranged from 132 to 180 C, time from 10 to 90 min and Oxalic Acid loadings from 0.01 to 0.038 g/g solids. Separate maxima were found for enzymatic saccharification and hemicellulose fermentation, respectively, with the condition for maximum saccharification being significantly more severe. Ethanol production was affected by reaction temperature more than by Oxalic Acid and reaction time over the ranges examined. The effect of reaction temperature was significant at a 95% confidence level in its effect on ethanol production. Oxalic Acid and reaction time were statistically significant at the 90% level. The highest ethanol concentration (20 g/l) was obtained after 48 h with an ethanol volumetric production rate of 0.42 g ethanol l � 1 h � 1 . The ethanol yield after SSF with P. stipitis was significantly higher than predicted by sequential saccharification and fermentation of substrate pretreated under the same condition. This was attributed to the secretion of b-glucosidase by P. stipitis. During SSF, free extracellular b-glucosidase activity was 1.30 pNPG U/g with P. stipitis, while saccharification without the yeast was 0.66 pNPG U/g. Published by Elsevier Ltd.
-
simultaneous saccharification and ethanol fermentation of Oxalic Acid pretreated corncob assessed with response surface methodology
Bioresource Technology, 2009Co-Authors: Rita C L B Rodrigues, Thomas W. JeffriesAbstract:Response surface methodology was used to evaluate optimal time, temperature and Oxalic Acid concentration for simultaneous saccharification and fermentation (SSF) of corncob particles by Pichia stipitis CBS 6054. Fifteen different conditions for pretreatment were examined in a 2 3 full factorial design with six axial points. Temperatures ranged from 132 to 180 C, time from 10 to 90 min and Oxalic Acid loadings from 0.01 to 0.038 g/g solids. Separate maxima were found for enzymatic saccharification and hemicellulose fermentation, respectively, with the condition for maximum saccharification being significantly more severe. Ethanol production was affected by reaction temperature more than by Oxalic Acid and reaction time over the ranges examined. The effect of reaction temperature was significant at a 95% confidence level in its effect on ethanol production. Oxalic Acid and reaction time were statistically significant at the 90% level. The highest ethanol concentration (20 g/l) was obtained after 48 h with an ethanol volumetric production rate of 0.42 g ethanol l � 1 h � 1 . The ethanol yield after SSF with P. stipitis was significantly higher than predicted by sequential saccharification and fermentation of substrate pretreated under the same condition. This was attributed to the secretion of b-glucosidase by P. stipitis. During SSF, free extracellular b-glucosidase activity was 1.30 pNPG U/g with P. stipitis, while saccharification without the yeast was 0.66 pNPG U/g. Published by Elsevier Ltd.
Carol A. Clausen - One of the best experts on this subject based on the ideXlab platform.
-
copper tolerance of brown rot fungi time course of Oxalic Acid production
International Biodeterioration & Biodegradation, 2003Co-Authors: Frederick Green, Carol A. ClausenAbstract:Abstract The increase in the use of non-arsenical copper-based wood preservatives in response to environmental concerns has been accompanied by interest in copper-tolerant decay fungi. Oxalic Acid production by brown-rot fungi has been proposed as one mechanism of copper tolerance. Fifteen brown-rot fungi representing the genera Postia , Wolfiporia , Meruliporia , Gloeophyllum , Laetiporus , Coniophora , Antrodia , Serpula , and Tyromyces were evaluated for Oxalic Acid production bi-weekly in southern yellow pine (SYP) blocks treated with 1.2% ammoniacal copper citrate (CC). Eleven fungi were designated copper-tolerant based upon weight loss in CC-treated blocks. After 2 weeks, these fungi produced 2–17 times more Oxalic Acid in CC-treated blocks than in untreated blocks. After 10 weeks, weight loss ranged from 32% to 57% in CC-treated SYP. Four fungi were copper sensitive, producing low levels of Oxalic Acid and minimal weight loss in CC-treated blocks. Rapid induction of Oxalic Acid appeared to correlate closely with copper tolerance. We conclude that the brown-rot fungi tested that were able to exceed and maintain an Oxalic Acid concentration of ⩾600 μmol / g effectively decayed SYP treated with CC.
-
correlation between Oxalic Acid production and copper tolerance in wolfiporia cocos
International Biodeterioration & Biodegradation, 2000Co-Authors: Carol A. Clausen, B M Woodward, Frederick Green, J W Evans, Rodney C. DegrootAbstract:The increased interest in copper-based wood preservatives has hastened the need for understanding why some fungi are able to attack copper-treated wood. Due in part to accumulation of Oxalic Acid by brown-rot fungi and visualization of copper oxalate crystals in wood decayed by known copper-tolerant decay fungi, Oxalic Acid has been implicated in copper tolerance by the formation of copper oxalate crystals. Nineteen isolates of the brown-rot fungus Wolfiporia cocos were evaluated for Oxalic Acid production and weight loss on wood treated with 1.2% copper citrate. Twelve of 19 isolates that caused moderate to high weight losses in copper citrate-treated wood produced low Oxalic Acid in liquid culture, whereas isolates with high Oxalic Acid production had low weight losses in treated wood. Seven W. cocos isolates demonstrated enhanced weight loss in Cu-treated wood. Wood weight loss was unaffected by the presence of copper citrate for two W. cocos isolates and weight loss was lower for 10 isolates compared to weight losses in untreated wood. Citrate did not significantly influence Oxalic Acid production in liquid culture. Previous hypotheses linking Oxalic Acid and copper tolerance were based upon observations of single isolates of Postia and Tyromyces. Although most isolates produced more Oxalic Acid in copper citrate-treated wood than in untreated wood, we found no statistical relationship between the amount of Oxalic Acid production in liquid culture or wood and copper tolerance in W. cocos. Production of Oxalic Acid does not seem to be the factor controlling copper tolerance in W. cocos. The diversity seen within W. cocos demonstrates that caution should be used when reporting results, so that generalizations are not based on the behavior of a single isolate.
M Neumannspallart - One of the best experts on this subject based on the ideXlab platform.
-
photoelectrocatalytic degradation of 4 chlorophenol and Oxalic Acid on titanium dioxide electrodes
Chemosphere, 2003Co-Authors: G Waldner, M Pourmodjib, R Bauer, M NeumannspallartAbstract:Photocatalytically active thin TiO2 films were produced by spin-coating or dip-coating an alkoxy precursor onto a transparent conducting electrode substrate and by thermal oxidation of titanium metal. The thin films were used to study the photoelectrocatalytic or photoelectrochemical degradation of Oxalic Acid and 4-chlorophenol (4-CP) under near UV (monochromatic, 365 nm) light irradiation. Degradation was monitored by a variety of methods. In the course of Oxalic Acid degradation, CO2 formation accounted for up to 100% of the total organic carbon degradation for medium starting concentrations; for the degradation of 4-CP, less CO2 was detected due to the higher number of oxidation steps, i.e. intermediates. Incident-photon-to-current conversion efficiency, educt degradation and product formation as well as Faradaic efficiencies were calculated for the degradation experiments. Quantum yields and Faradaic efficiencies were found to be strongly dependent on concentration, with maximum values (quantum yield) around 1 for the highest concentrations of Oxalic Acid. 2002 Elsevier Science Ltd. All rights reserved.
-
photoelectrocatalytic degradation of 4 chlorophenol and Oxalic Acid on titanium dioxide electrodes
Chemosphere, 2003Co-Authors: G Waldner, M Pourmodjib, R Bauer, M NeumannspallartAbstract:Abstract Photocatalytically active thin TiO2 films were produced by spin-coating or dip-coating an alkoxy precursor onto a transparent conducting electrode substrate and by thermal oxidation of titanium metal. The thin films were used to study the photoelectrocatalytic or photoelectrochemical degradation of Oxalic Acid and 4-chlorophenol (4-CP) under near UV (monochromatic, 365 nm) light irradiation. Degradation was monitored by a variety of methods. In the course of Oxalic Acid degradation, CO2 formation accounted for up to 100% of the total organic carbon degradation for medium starting concentrations; for the degradation of 4-CP, less CO2 was detected due to the higher number of oxidation steps, i.e. intermediates. Incident-photon-to-current conversion efficiency, educt degradation and product formation as well as Faradaic efficiencies were calculated for the degradation experiments. Quantum yields and Faradaic efficiencies were found to be strongly dependent on concentration, with maximum values (quantum yield) around 1 for the highest concentrations of Oxalic Acid.
Ramon Monterodeespinosa - One of the best experts on this subject based on the ideXlab platform.
-
catalytic ozonation of Oxalic Acid in an aqueous tio2 slurry reactor
Applied Catalysis B-environmental, 2002Co-Authors: Fernando J Beltran, F J Rivas, Ramon MonterodeespinosaAbstract:Abstract The ozonation of Oxalic Acid has been carried out in an agitated slurry semibatch reactor where powdered TiO2 has been used as a catalyst. The presence of TiO2 catalyst significantly improved the ozonation rate of Oxalic Acid compared to the results from non-catalytic ozonation. For gas flow rates higher than 12 l h−1 and agitation speed above 100 rpm, the catalytic process rate was chemically controlled. The kinetic study led to a zero-order kinetics for both the non-catalytic and catalytic ozonations. These experimental findings were corroborated by a mechanism of reactions. This kinetics also supported experimental results at different temperatures, ozone partial pressure and mass of catalyst per slurry volume. At low gas flow rate, where both mass transfer and chemical reaction controlled the process rate, the external gas to liquid mass transfer coefficient was also determined.
-
kinetics of catalytic ozonation of Oxalic Acid in water with activated carbon
Industrial & Engineering Chemistry Research, 2002Co-Authors: Fernando J Beltran, F J Rivas, Lidia A Fernandez, And Pedro M Alvarez, Ramon MonterodeespinosaAbstract:The ozonation kinetics of Oxalic Acid in water in the presence of an activated carbon has been investigated at Acid pH. The presence of the activated carbon significantly enhances the degradation rate of Oxalic Acid if compared to single ozonation and single adsorption. According to total organic carbon measurements, nearly complete mineralization of Oxalic Acid can be achieved depending on the experimental conditions. The presence of tert-butyl alcohol, which scarcely adsorbs on the carbon surface at the conditions investigated, led to a significant reduction of the Oxalic Acid removal rate. Consequently, experimental results suggest that the reaction proceeds in the water phase between Oxalic Acid and oxidant species, likely hydroxyl radicals, coming from the ozone decomposition on the carbon surface. The proposed mechanism yielded a first-order kinetics with respect to ozone, close to the 0.8 order experimentally observed. Also, the energy of activation was found to be approximately 15 kcal mol-1.
