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Papers by ROBERTO VALENZUELA
Journal of the Chilean Chemical Society, 2017
In order to understand the relation between chemical composition, microscopic structure and enzym... more In order to understand the relation between chemical composition, microscopic structure and enzymatic digestibility, different Eucalyptus globulus wood pretreated samples were examined. Pretreated materials obtained by steam explosion and autohydrolysis were compared with those obtained by organosolv and kraft processes. Chemical analyses of pretreated materials showed a decrease in the content of xylans, except in the kraft pulp. FT-IR spectra showed that the residual lignin in autohydrolysis pulp had experienced greater changes compared to those in steam explosion and organosolv pulps, whereas minor changes in lignin kraft pulp were observed. The fiber morphology indicated that autohydrolysis pretreatment was the most aggressive treatment. Reduction in the content of lignin and its redistribution on the fiber wall were confirmed through confocal laser microscopy. The formation of discrete lignin droplets deposited on the surface of the fibers was observed in all pretreatments, with a higher frequency in organosolv followed by steam explosion. A significant increase in enzymatic accessibility was achieved in organosolv, autohydrolysis and steam explosion pulps, due to xylans removal combined with lignin redistribution. Homogeneous lignin distribution and higher xylan content may be related to the low enzymatic hydrolysis efficiency in kraft pulp.
Industrial Crops and Products, 2016
Pinus radiata is an appropriate feedstock for the production of second-generation bioethanol thro... more Pinus radiata is an appropriate feedstock for the production of second-generation bioethanol through a biochemical platform due to its high content of fermentable sugars. However, because of this tree's recalcitrance, a suitable pretreatment is necessary. In this paper, the effect of the concentration of H 2 SO 4 as a catalyst for the organosolv pretreatment for this raw material was studied. It was determined that a concentration of 1.1% of H 2 SO 4 promotes structural and morphological changes, such as the formation of lignin droplets, which increase the digestibility of the pretreated material to achieve an efficient conversion of cellulose to glucose of 94% using the proper dosage of a last-generation cellulase complex. Because of the good digestibility of the pretreated material obtained, it was possible to obtain high concentrations of ethanol, reaching 85.01 g/L after 72 h of reaction, working with fed-batch simultaneous saccharification and fermentation at 40 • C at high substrate loadings using the thermotolerant strain of Saccharomyces cerevisiae IR2-9a. The importance of obtaining high concentrations of ethanol is that if the concentrations are above 4%, the cost of the distillation process is decreased.
Journal of the Chilean Chemical Society, 2009
Tribromophenol (TBP) is a halogenated phenol mainly used as an intermediate of flame retardants i... more Tribromophenol (TBP) is a halogenated phenol mainly used as an intermediate of flame retardants in the electronics manufacturing industry as well as a fungicide in the wood industry to prevent fungal wood stain and decay. As a result of this massive use, its bio-availability, toxicity, and environmental fate are of increasing concern worldwide. TBP degradation by a catechol (CAT)-driven Fenton reaction was studied. In order to achieve the best yield in TBP degradation, an experimental design was applied for multivariate optimization of the experimental degrading system variables. At optimized concentrations, the CAT-driven Fenton reaction yielded 75% TBP degradation in 2 h at room temperature. The multivariate optimization showed that the highest TBP degradation (1 mol base) was obtained at a ratio of CAT: FeCl 3 : H 2 O 2 = 0.150 : 0.211: 5.100 at pH = 3.4. A time course degradation of TBP comparing the CAT-driven Fenton reaction with the classical Fenton reaction is also presented. During the first hours of reaction (up to 8h), increased degradation efficiencies were observed in the CAT-driven Fenton reaction in comparison with the conventional Fenton reaction. Possible causes for the observed behavior are also discussed.
Journal of Experimental Nanoscience, 2012
β-glucosidase from Trichoderma reesei was immobilized on synthetic superparamagnetic magnetite (F... more β-glucosidase from Trichoderma reesei was immobilized on synthetic superparamagnetic magnetite (Fe 3 O 4) nanoparticles with a mean diameter of 10 nm and were used to supplement cellulase in the enzymatic hydrolysis of three substrates: wheat straw pretreated by steam explosion, Eucalyptus globulus pretreated by hydrothermolysis and pulp from hydrothermolysis followed by an alkaline extraction. The hydrolysis yields for each pretreated material, using immobilized β-glucosidase and free cellulase, were 76.1%, 83.6% and 75.6%, respectively and resulted in an improved hydrolysis yields compared with only cellulase. These yields were at most 10% lower than yields reached with free enzymes. The immobilized β-glucosidase was magnetically recovered and reused twice. The differences in the hydrolysis yields were not significant (p>0.05) in the case of steam exploded wheat straw and pulp from hydrothermolysis and alkaline extraction. The immobilization of enzymes provides an opportunity to reduce the costs of enzymes in the bioethanol production process.
Journal of Clinical Anesthesia, 1997
To ~unq cost containment ac'tivities in anesthesiology: and to determine to what extent departmen... more To ~unq cost containment ac'tivities in anesthesiology: and to determine to what extent departments use cost pobri~s and guidelines. Design: Muil sunq. Setting: Academic and large nonacademic anesthesiolog? departments. Measurements and Main Results: 147 responding departments answrrred 20 questions. ?S% of suroqs were returned. 90 responder-c idrntijird themselves as academic departments and 57 responders as nonacademic. 73 7~ of d@artments reported pressure from hospital administmtor.c to reduce ane.sthesia ro$ts. The most common cost-saving activity, used 4 907~ of departments, is improving operating room (OR) utilization. 53% of all departments have poliries or <guidelines to contain d7ug costs, while 48% of departments have these to contain other product costs. LIepartmrnts l$orting-themselves as academic genflally reported greater-use of cost poke% (:onclusions: Anrsthrsiolo,p departments are QpPnencingpressztre to reduce costs and the majority have cost policies rind CguideLine.~ roncernlng utilization of 0R.s and anesthetic drugs. :Aradrmir anesthesiolog?; drpartmPnts may be expurimring more cost-containment pressure than nonacademic departments.
Journal of Clinical Anesthesia, 1995
To contain costs, departments of anesthesiology must control the use of new, expensive drugs. Con... more To contain costs, departments of anesthesiology must control the use of new, expensive drugs. Conflicts with pharmaceutical companies can arise when they promote drug sales. Pharmaceutical company sales represent anesthesiology department expenses. Anesthesiologists hold diverse opinions on this clash of interests, on the proper roles of pharmaceutical sales representatives in anesthesiology departments, and on the ethics of accepting industry gifts. Our department has managed pharmaceutical sales activities by encouraging discussion of the ethics and legal limits of industry gifts, by banning sales representatives from bringing food into the department, and by adopting The American Medical Association Guidelines on Gifts.
Journal of Alloys and Compounds, 2009
Superparamagnetic magnetite nanoparticles (mean diameter 10 nm) were synthesized using the co-pre... more Superparamagnetic magnetite nanoparticles (mean diameter 10 nm) were synthesized using the co-precipitation route from Fe 2+ /Fe 3+ in aqueous solutions (molar ratio 1:2) by adding a base under mechanical stirring at 10,000 rpm. This stirring velocity was found to be ...
International Biodeterioration & Biodegradation, 2008
Metals can potentially play a role in the non-enzymatic processes involved in wood biodegradation... more Metals can potentially play a role in the non-enzymatic processes involved in wood biodegradation. Dihydroxybenzenes reduce Cu (II)Cu (I), which then react with H2O2 driving a Fenton reaction. In this work the degradation of veratryl alcohol (VA), the simplest ...
Journal of the Chilean Chemical Society, 2017
In order to understand the relation between chemical composition, microscopic structure and enzym... more In order to understand the relation between chemical composition, microscopic structure and enzymatic digestibility, different Eucalyptus globulus wood pretreated samples were examined. Pretreated materials obtained by steam explosion and autohydrolysis were compared with those obtained by organosolv and kraft processes. Chemical analyses of pretreated materials showed a decrease in the content of xylans, except in the kraft pulp. FT-IR spectra showed that the residual lignin in autohydrolysis pulp had experienced greater changes compared to those in steam explosion and organosolv pulps, whereas minor changes in lignin kraft pulp were observed. The fiber morphology indicated that autohydrolysis pretreatment was the most aggressive treatment. Reduction in the content of lignin and its redistribution on the fiber wall were confirmed through confocal laser microscopy. The formation of discrete lignin droplets deposited on the surface of the fibers was observed in all pretreatments, with a higher frequency in organosolv followed by steam explosion. A significant increase in enzymatic accessibility was achieved in organosolv, autohydrolysis and steam explosion pulps, due to xylans removal combined with lignin redistribution. Homogeneous lignin distribution and higher xylan content may be related to the low enzymatic hydrolysis efficiency in kraft pulp.
Industrial Crops and Products, 2016
Pinus radiata is an appropriate feedstock for the production of second-generation bioethanol thro... more Pinus radiata is an appropriate feedstock for the production of second-generation bioethanol through a biochemical platform due to its high content of fermentable sugars. However, because of this tree's recalcitrance, a suitable pretreatment is necessary. In this paper, the effect of the concentration of H 2 SO 4 as a catalyst for the organosolv pretreatment for this raw material was studied. It was determined that a concentration of 1.1% of H 2 SO 4 promotes structural and morphological changes, such as the formation of lignin droplets, which increase the digestibility of the pretreated material to achieve an efficient conversion of cellulose to glucose of 94% using the proper dosage of a last-generation cellulase complex. Because of the good digestibility of the pretreated material obtained, it was possible to obtain high concentrations of ethanol, reaching 85.01 g/L after 72 h of reaction, working with fed-batch simultaneous saccharification and fermentation at 40 • C at high substrate loadings using the thermotolerant strain of Saccharomyces cerevisiae IR2-9a. The importance of obtaining high concentrations of ethanol is that if the concentrations are above 4%, the cost of the distillation process is decreased.
Journal of the Chilean Chemical Society, 2009
Tribromophenol (TBP) is a halogenated phenol mainly used as an intermediate of flame retardants i... more Tribromophenol (TBP) is a halogenated phenol mainly used as an intermediate of flame retardants in the electronics manufacturing industry as well as a fungicide in the wood industry to prevent fungal wood stain and decay. As a result of this massive use, its bio-availability, toxicity, and environmental fate are of increasing concern worldwide. TBP degradation by a catechol (CAT)-driven Fenton reaction was studied. In order to achieve the best yield in TBP degradation, an experimental design was applied for multivariate optimization of the experimental degrading system variables. At optimized concentrations, the CAT-driven Fenton reaction yielded 75% TBP degradation in 2 h at room temperature. The multivariate optimization showed that the highest TBP degradation (1 mol base) was obtained at a ratio of CAT: FeCl 3 : H 2 O 2 = 0.150 : 0.211: 5.100 at pH = 3.4. A time course degradation of TBP comparing the CAT-driven Fenton reaction with the classical Fenton reaction is also presented. During the first hours of reaction (up to 8h), increased degradation efficiencies were observed in the CAT-driven Fenton reaction in comparison with the conventional Fenton reaction. Possible causes for the observed behavior are also discussed.
Journal of Experimental Nanoscience, 2012
β-glucosidase from Trichoderma reesei was immobilized on synthetic superparamagnetic magnetite (F... more β-glucosidase from Trichoderma reesei was immobilized on synthetic superparamagnetic magnetite (Fe 3 O 4) nanoparticles with a mean diameter of 10 nm and were used to supplement cellulase in the enzymatic hydrolysis of three substrates: wheat straw pretreated by steam explosion, Eucalyptus globulus pretreated by hydrothermolysis and pulp from hydrothermolysis followed by an alkaline extraction. The hydrolysis yields for each pretreated material, using immobilized β-glucosidase and free cellulase, were 76.1%, 83.6% and 75.6%, respectively and resulted in an improved hydrolysis yields compared with only cellulase. These yields were at most 10% lower than yields reached with free enzymes. The immobilized β-glucosidase was magnetically recovered and reused twice. The differences in the hydrolysis yields were not significant (p>0.05) in the case of steam exploded wheat straw and pulp from hydrothermolysis and alkaline extraction. The immobilization of enzymes provides an opportunity to reduce the costs of enzymes in the bioethanol production process.
Journal of Clinical Anesthesia, 1997
To ~unq cost containment ac'tivities in anesthesiology: and to determine to what extent departmen... more To ~unq cost containment ac'tivities in anesthesiology: and to determine to what extent departments use cost pobri~s and guidelines. Design: Muil sunq. Setting: Academic and large nonacademic anesthesiolog? departments. Measurements and Main Results: 147 responding departments answrrred 20 questions. ?S% of suroqs were returned. 90 responder-c idrntijird themselves as academic departments and 57 responders as nonacademic. 73 7~ of d@artments reported pressure from hospital administmtor.c to reduce ane.sthesia ro$ts. The most common cost-saving activity, used 4 907~ of departments, is improving operating room (OR) utilization. 53% of all departments have poliries or <guidelines to contain d7ug costs, while 48% of departments have these to contain other product costs. LIepartmrnts l$orting-themselves as academic genflally reported greater-use of cost poke% (:onclusions: Anrsthrsiolo,p departments are QpPnencingpressztre to reduce costs and the majority have cost policies rind CguideLine.~ roncernlng utilization of 0R.s and anesthetic drugs. :Aradrmir anesthesiolog?; drpartmPnts may be expurimring more cost-containment pressure than nonacademic departments.
Journal of Clinical Anesthesia, 1995
To contain costs, departments of anesthesiology must control the use of new, expensive drugs. Con... more To contain costs, departments of anesthesiology must control the use of new, expensive drugs. Conflicts with pharmaceutical companies can arise when they promote drug sales. Pharmaceutical company sales represent anesthesiology department expenses. Anesthesiologists hold diverse opinions on this clash of interests, on the proper roles of pharmaceutical sales representatives in anesthesiology departments, and on the ethics of accepting industry gifts. Our department has managed pharmaceutical sales activities by encouraging discussion of the ethics and legal limits of industry gifts, by banning sales representatives from bringing food into the department, and by adopting The American Medical Association Guidelines on Gifts.
Journal of Alloys and Compounds, 2009
Superparamagnetic magnetite nanoparticles (mean diameter 10 nm) were synthesized using the co-pre... more Superparamagnetic magnetite nanoparticles (mean diameter 10 nm) were synthesized using the co-precipitation route from Fe 2+ /Fe 3+ in aqueous solutions (molar ratio 1:2) by adding a base under mechanical stirring at 10,000 rpm. This stirring velocity was found to be ...
International Biodeterioration & Biodegradation, 2008
Metals can potentially play a role in the non-enzymatic processes involved in wood biodegradation... more Metals can potentially play a role in the non-enzymatic processes involved in wood biodegradation. Dihydroxybenzenes reduce Cu (II)Cu (I), which then react with H2O2 driving a Fenton reaction. In this work the degradation of veratryl alcohol (VA), the simplest ...