Facultad de Quimica

A plate assay using the Fe (II) selective dye, ferrozine, for detecting wood-rot fungi with Fe (III) reductive abilities, was developed. The assay is fast, simple and, in most cases, more sensitive than the corresponding liquid medium test. The brown rot fungi, Gloeophyllum ...

Ethanol derived from biomass has the potential to be a renewable transportation fuel that can replace gasoline. The demand for oxygenated fuels is increasing rapidly. The use of bioethanol can save non-renewable energy consumption and reduce greenhouse emissions. The largest feedstock for ethanol is lignocellulosic biomass. Cellulose is intrinsically resistant to enzymatic attack, and is further protected by the surrounding matrix of lignin and hemicelluloses. Therefore, lignocellulosic materials must be pretreated to make the cellulose more accessible to hydrolysis. In this work, the organosolv acetone-water pretreatment conditions for Pinus radiata D. Don chips were optimized to obtain higher ethanol yield. An organosolv pretreated material produced at 195 • C, 5 min, pH 2.0 and acetone:water 1:1 of ratio resulted in 99.5% of ethanol yield. Under these conditions, the experimental H-factor was close to 2800.

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 H 2 O 2 driving a Fenton reaction. In this work the degradation of veratryl alcohol (VA), the simplest non-phenolic lignin model compound, via a cuprous Fenton reaction mediated by 1,2-dihydroxybenzene (catechol, CAT) was studied. A factorial experimental design was performed to assess the impact of several experimental variables including, pH, and CAT, CuCl 2 and H 2 O 2 concentrations on VA degradation. Optimized conditions were determined using a response surface modeling methodology (RSM). The greatest amount of VA degradation occurred at a CAT:CuCl 2 :H 2 O 2 ratio of 0.287:0.313:4.062, a pH of 3.6. A time-course measurement for VA degradation was performed under these experimental conditions and after an 8 h reaction period, 31% of the VA was degraded. Under the same experimental conditions, VA degradation by an iron CAT-driven Fenton reaction was more effective than the copper CAT-driven Fenton reaction. In a similar experiment, carboxymethyl cellulose (CMC) depolymerization was also determined. Only the iron CAT-driven Fenton reaction was found to depolymerize CMC. We suggest that the greater redox potential of the Fe(III)CAT complex compared to the Cu(II)CAT complex would dictate that under most environmental conditions, degradation of VA would occur by the iron complex only. This research has important implications for the mechanisms of brown rot fungal degradation in wood because it eliminates a pathway that had previously been proposed as a mechanism explaining free radical generation in the oxidative depolymerization of cellulose in the cell wall. r

Dihydroxybenzenes reduce Fe(III) to Fe(II), which react with H 2 O 2 driving a Fenton reaction. This non-enzymic mechanism operates in wood degradation by brown-rot fungi, which mainly degrade wood carbohydrates and, to a lesser extent, lignin. Consequently, less attention has been focussed on lignin transformation by these organisms. In this work, the degradation of veratryl alcohol (VA), the simplest lignin model compound, via a Fenton reaction driven by 1,2-dihydroxybenzene (catechol, CAT) was studied. Multivariate analysis performed in order to determine the relationship between pH and concentrations of CAT, FeCl 3 and H 2 O 2 showed that the highest VA degradation, 1 mol base, was obtained at the CAT:FeCl 3 :H 2 O 2 ratio of 0.375:0.375:5.0 at pH 3.4. Under these reaction conditions, VA degradation and mineralisation were, respectively, 3.8 and almost 40 times greater than for a Fe(II)-Fenton reaction. r

A dihydroxybenzenes(DHB)-driven Fenton reaction was found to be more efficient than a simple Fenton reaction based on Å OH radical and activated species production. The reason for this enhanced reactivity by [Fe DHB] complexes is not well understood, but results suggest that it may be explained by the formation of oxidation species different from those formed during the classic Fenton reactions. In previous work, greater concentrations, and more sustained production of Å OH over time were observed in DHB driven Fenton reactions versus neat Fenton and Fenton-like reactions. In this work, chemiluminescence (CL) was monitored, and compared to Å OH production kinetics. The CL of the DHB-driven Fenton reaction was shorter than that for sustained production of Å OH. CL appears to have been caused by excited Fe(IV) species stabilized by the DHB ligands initially formed in the reaction. Formation of this species would have to have occurred by the reaction between Å OH and Fe(III) in a DHB complex.

This paper discusses the degradation of the antibiotic ampicillin (AMP) by Fenton and photo-Fenton reactions. The influence of the three main variables that govern the degradation kinetic (pH, H 2 O 2 and Fe(II) concentrations) was evaluated with a circumscribed central composite (CCC) model and a response surface methodology (RSM). The optimal conditions for Fenton and photo-Fenton reactions are very similar: pH 3.5, around 400 mol L −1 H 2 O 2 and 87 mol L −1 Fe(II). Under such optimized conditions, the complete AMP removal was reached after 10 min and 3 min for Fenton and photo-Fenton reactions, respectively. A very similar removal profile in the first 2 min of reaction was observed for both systems with a high degree of degradation (close to 90%). After a 2-min treatment, the Fenton reaction became slower, and the IR product analysis suggests the formation of different oxidation intermediates. This observation was confirmed by the COD and TOC evolution during the reactions. The oxidation degree, measured as Average Oxidation State (AOS), indicates that the photo-Fenton reaction produces faster most of the oxidation intermediates. The antibacterial activity (AA) of the oxidized samples was determined using the inhibition halo methodology on agar plates cultured with Staphylococcus aureus bacteria. The course of AA is concomitant with the AMP removal, which indicates that the long-term intermediates do not present antibiotic properties.

Eucalyptus globulus is an important forestry species for wood and pulp industry; however, its low cold resistance is a serious disadvantage. In this work, chemometric techniques were applied on the leaves' free amino acid content of different E. globulus genotypes in order to select cold tolerant genotypes. Pattern recognition methods based on regularized discriminant analysis (RDA) were used to classify the genotypes by cold resistance using samples' foliar damages as reference of cold resistance. Correlation between the amino acids content and cold resistance of genotypes was determined from a partial least squares (PLS) model. RDA models showed an excellent classification of genotypes (100% of correctly assigned genotypes in external validation), especially when RDA was reduced to quadratic discriminant analysis (QDA). Arg, Tyr and Ala, showed the highest correlations with the foliar damage in the PLS model and they could be responsible to improve cold resistance to the studied genotypes.