Browsing by Author "Estenoz, Diana"
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Item A thermostable laccase from Thermus sp. 2.9 and its potential for delignifcation of Eucalyptus biomass(2019-04-02) Navas, Laura; Martinez, Fernando; Taverna, María E.; Fetherol, Morgan; Eltis, Lindsay; Nicolau, Verónica V.; Estenoz, Diana; Campos, Eleonora; Benintende, Graciela; Berreta, MarceloLaccases are multicopper oxidases that are being studied for their potential application in pretreatment strategies of lignocellulosic feedstocks for bioethanol production. Here, we report the expression and characterization of a predicted laccase (LAC_2.9) from the thermophilic bacterial strain Thermus sp. 2.9 and investigate its capacity to delignify lignocellulosic biomass. The purified enzyme displayed a blue color typical of laccases, showed strict copper dependence and retained 80% of its activity after 16 h at 70 °C. At 60 °C, the enzyme oxidized 2,2′-azino-di-(3-ethylbenzthiazoline sulfonate) (ABTS) and 2,6-dimethoxyphenol (DMP) at optimal pH of 5 and 6, respectively. LAC_2.9 had higher substrate specificity (kcat/KM) for DMP with a calculated value that accounts for one of the highest reported for laccases. Further, the enzyme oxidized a phenolic lignin model dimer. The incubation of steam-exploded eucalyptus biomass with LAC_2.9 and 1-hydroxybenzotriazole (HBT) as mediator changed the structural properties of the lignocellulose as evidenced by Fourier transform infrared (FTIR) spectroscopy and thermo-gravimetric analysis (TGA). However, this did not increase the yield of sugars released by enzymatic saccharification. In conclusion, LAC_2.9 is a thermostable laccase with potential application in the delignification of lignocellulosic biomass.Item Ácido poliláctico a partir de lactosuero: I. Síntesis de lactido.(2017-10-18) Garnero, Paula Carolina; Chiappero, Lucio Rafael; Nicolau, Verónica V.; Estenoz, DianaEl ácido poliláctico (APL) es un biopolímero termoplástico que ha encontrado numerosas aplicaciones en el campo de la medicina y en la fabricación de envases descartables pero su costo es aún elevado comparado con los plásticos sintéticos tradicionales. Una de las estrategias estudiadas para abaratar los costos es emplear como materia prima desechos agrícolas o lactosuero, subproductos que son abundantes en nuestro país. El APL puede obtenerse por apertura de anillo del dímero lactido y sus propiedades estarán directamente influenciadas por la calidad del monómero. El objetivo final de la investigación es diseñar y optimizar un proceso de obtención de APL a partir de lactosuero. En este trabajo se presenta la primera etapa de la investigación en la cual se estudió la síntesis de lactido vía un proceso de oligomerización-depolimerización tanto a partir de ácido láctico como de lactato de etilo [1]. La oligomerización del ácido láctico se llevó a cabo a 180 °C (6 h en atmósfera de nitrógeno - 5 h a 70 mmHg) y la depolimerización a 210 °C (5 h a 70 mmHg con 0,5% p/p de cloruro estañoso como catalizador) [2]. De modo similar, la oligomerización del lactato de etilo se realizó a 180 ºC (6 h en atmósfera de nitrógeno con 1% p/p de octoato de estaño como catalizador - 5 h a 70 mmHg) y la depolimerización a 180 ºC (5 h a 70 mmHg). Finalmente se obtuvo APL por apertura de anillo del dímero lactido a 170 ªC empleando alcohol bencílico y octoato de estaño como iniciador y catalizador, respectivamente [3]. Se emplearon técnicas volumétricas, cromatográficas (SEC y GC) y espectroscópicas (1H RMN) para la caracterización de los monómeros, los oligómeros, el lactido y el APL [4]. Los cromatogramas y espectros obtenidos por GC y RMN confirmaron la estructura del compuesto cíclico.Item Additives based on vegetable biomass to improve the stabilisation of expansive clay soil(2021-05) Orlandi, Sandra; Taverna, María E.; Villada, Yurany A.; Pique, Teresa; Laskowski, Cecilia; Nicolau, Verónica V.; Estenoz, Diana; Manzanal, DiegoThis paper investigates the effect of different bio-based additives on the expansiveness of an Argentinian natural clayey soil (CR-clay). CR-clay was characterised to determine (a) the Atterberg parameters and other index properties, (b) the particle size distribution by laser diffraction, (c) the specific surface area (Se) and cationic exchange capacity by the methylene blue method, (d) the mineralogy by using X-ray diffraction, (e) the functional groups by Fourier transform infrared spectroscopy (FTIR) and (f) the free swelling and swelling pressure by using an odometer. Starches from potato, cassava, corn and rice flour; seeds and derivatives from flax, sunflower and quinoa; kraft lignin; and lignosulfonates were evaluated as soil stabilisation additives on the basis of measurements of Atterberg parameters. Reductions in the soil plasticity index (PI) between 10 and 60% were generally observed. Lignins exhibited a very good balance between the ability to improve soil stabilisation, low costs, environment-friendliness and availability. In particular, kraft lignin showed high performance as a CR-clay stabiliser with a PI reduction of 46%. The stabilisation mechanism of lignin and CR-clay blends was investigated using Z potential and FTIR. Based on the experimental results, lignins constitute promising alternatives to the additives used as stabilisers of expansive soils, particularly for reducing free-swell and swelling pressure.Item Bio-composite Films Based on Alginate and Rice Husk Tar Microparticles Loaded with Eugenol for Active Packaging(2022-01-29) Taverna, María E.; Busatto, Carlos Alberto; Saires, Paula J.; Bertero, Melisa Paola; Sedran, Ulises A.; Estenoz, DianaThis work focused on the valorization of tar derived from rice husk pyrolysis as a precursor of matrices for the encapsulation of active principles. In this regard, the development of novel films based on alginate and eugenol-loaded tar microparticles with suitable mechanical properties and antibacterial activity was studied. Tar microparticles loaded with eugenol were incorporated into sodium alginate films and the effect on the mechanical, thermal and humidity resistance properties were determined, as well as the antimicrobial activity. Films with different crosslinking degrees were also prepared using CaCl2, and the eugenol controlled release profiles were evaluated. Crosslinked films exhibited improved mechanical and humidity resistance properties, as well as a lower release rate of eugenol in water. The antimicrobial studies showed that eugenol-loaded films present a higher antimicrobial activity against Staphylococcus aureus. Alginate/eugenol-loaded tar microparticles composites showed an enhancement of antibacterial properties and suitable physical characteristics to be used in active packaging applications.Item Caracterización espectroscópica por resonancia magnética nuclear de resina de urea-formaldehído(Secyt UTN Facultad Regional San Francisco, 2020-10) Caula, María Andrea; Estenoz, Diana; Nicolau, Verónica V.Las resinas base de urea formaldehído (U-F) se obtienen por reacción entre la urea (U) y el formaldehído (F) y se utilizan principalmente como adhesivos en la fabricación de paneles de madera. El mecanismo de reacción consiste en una hidroximetilación-condensación. En este trabajo se caracterizaron los productos de reacción generados durante la síntesis de resinas de U-F en condiciones ácidas y alcalinas en un rango de temperatura entre 38 y 90 °C. Para la caracterización se empleó resonancia magnética nuclear de protones y carbono y estudios de correlación nuclear.Item Decorative laminates based on phenolic resins modified with sodium lignosulfonate and kraft lignin: Evaluation of mechanical properties(2014-03) Taverna, María E.; Nicolau, Verónica V.; Ollearo, Rocío; Morán, Juan; Frontini, Patricia; Meira, Gregorio; Estenoz, DianaThe substitution of phenol in the production of resol-type phenolic resins by environmentally-friendly compounds such as lignin and its derivatives is of great technological and academic interest, due to the similarity between resols and the aromatic structure of lignins. However, lignins must be chemically-modified in order to increase their reactivity toward formaldehyde. In this work, the addition of commercial lignins (sodium lignosulfonate and Kraft-type) as partial replacement of phenol in the resols used for decorative laminates production is experimentally studied. The work involved: the characterization and reactivation of commercial lignins, the industrial synthesis of traditional and modified resols by replacement of 10 and 20% w/w of phenol, the industrial impregnation of Kraft-type papers with the produced resins and the production of laminates at laboratory and industrial scales. The mechanical performance of the laminates was deeply assesed by determining tensile modulus, bending strengh, biaxial flexural impact strenght and Mode- I Interlaminar Fracture Toughness in both processing directions. Modified laminates exhibited mechanical properties comparable with those of traditional laminates, indicating a negligible depreciation of them. Industrial tests were carried out at Centro S.A, San Francisco, Córdoba.Item Efecto de la incorporación de nanopartículas de lignina iónica en la cristalización de polióxido de etileno(2020-04) Taverna, María E.; Olmedo, Jorge; Busatto, Carlos Alberto; Zubitur, Manuela; Nicolau, Verónica V.; Estenoz, Diana; Müller, Alejandro J.El polióxido de etileno (POE) es un poliéter semicristalino cuya cinética de cristalización ha sido ampliamente estudiada tanto en el componente puro como en sus mezclas con otros polímeros amorfos y semicristalinos. Se han investigado materiales compuestos basados en mezclas de POE y lignina (polímero natural, amorfo, abundante y de bajo costo). La mezcla eficiente de estos polímeros depende en gran medida de la compleja estructura de la lignina. Se ha reportado la cinética de cristalización de la mezcla de POE y lignina proveniente de procesos de aislamiento Alcell y/o Kraft.2 En este trabajo se estudia la síntesis de nanopartículas de lignina de origen iónico y su empleo en la obtención de mezclas con POE. Específicamente, se evalúa la influencia de nanopartículas en la cinética de cristalización del POE.Item Efecto del ph en la síntesis de resinas de urea-formaldehído: caracterización y modelo matemático(XII Simposio Argentino de Polímeros (Los Cocos), 2017-10-18) Caula, María Andrea; Nicolau, Verónica V.; Estenoz, DianaSe estudió teórica y experimentalmente la hidroximetilación-condensación de la urea a pH 4 y 9 a temperaturas 38ºC, 48 ºC, 60 ºC, 70 ºC y 90 ºC para sistemas diluidos homogéneos. Para el seguimiento de la reacción se usaron técnicas volumétricas, cromatográficas, y espectroscópicas. Se desarrolló un modelo matemático que permite simular la hidroximetilación-condensación de la urea considerando las siguientes reacciones secundarias del formaldehído: hidratación/deshidratación y formación de poli(oximetilenglicol). El modelo fue ajustado y validado a partir de las mediciones. Los resultados teóricos mostraron muy buena concordancia con las mediciones.Item Effect of Kraft Lignin from Hardwood on Viscoelastic, Thermal, Mechanical and Aging Performance of High Pressure Laminates.(Waste and Biomass Valorization, 2017-07-10) Taverna, María E.; Tassara, Oriana; Morán, Juan; Nicolau, Verónica V.; Estenoz, Diana; Frontini, PatriciaIn this work, the synthesis and characterization of phenol-formaldehyde resols modified with 10, 20 and 30 wt% of Kraft lignin (a waste from pulp industry) from hardwood were studied. In all cases, the Kraft lignin was activated by hydroxymethylation. The resols characterization involved industrial measurements of free formaldehyde, viscosity, total solids and density. The resins were used for the industrial impregnation of Kraft-type paper and the production of laboratory laminates. The mechanical and thermal properties of the laminates were determined. Mechanical measurements included tensile, flexural, impact and interlaminar tests. Thermogravimetric and dynamic mechanical analysis were used for the thermal characterization. In addition, the aging of materials in water was studied. No significant differences in mechanical and thermal properties between traditional and modified materials were found with replacement up to 20 wt% of phenol. Modified laminates exhibited better water resistance due to the lignin hydrophobicity. This work was carried out in collaboration with Centro S.A., San Francisco, Córdoba, Argentina, a high pressure-laminates industry.Item Empleo de Lignosulfonatos en la síntesis de resinas de Fenol-Formaldehido. Caracterización e hidroximetilación.(2018-05-29) Chiappero, Lucio Rafael; Nicolau, Verónica V.; Estenoz, DianaLas resinas de fenol-formaldehído (PF) son polímeros sintéticos obtenidos por reacción entre el fenol (P) y el formaldehído (F). En la actualidad, la sustitución parcial del P por polímeros naturales, tales como las ligninas y sus derivados, constituye una alternativa, debido a la similitud existente entre el P y las estructuras a aromáticas presentes en la lignina. A diferencia del P que presenta 3 sitios reactivos en las posiciones orto- y para-, los anillos aromáticos (o radicales) de la lignina presentan sólo 1, 2 o ningún sitio reactivo orto- por anillo, ya que las posiciones para- están sustituidas (Fig. 1). La relación molar de los radicales aromáticos varía principalmente con el tipo de madera y las condiciones de pulpado (Peng et al., 1993), determinando la reactividad de las ligninas y las propiedades finales de los materiales que con ellas se produzcan. Los lignosulfonatos son el único tipo de lignina completamente soluble en agua en todo rango de pH debido a la presencia de grupos sulfonatos hidrofílicos y además están disponibles en gran cantidad y a un precio capaz de hacer atractiva la posibilidad de incorporarlos parcialmente en resinas de PF. La baja reactividad de la lignina hacia el F hace necesaria su modificación estructural previa, la cual puede realizarse por distintos métodos, siendo el más empleado para la síntesis de resinas de PF del tipo resol la hidroximetilación con F en medio alcalino (Alonso, 2001). En este trabajo se describe la caracterización e hidroximetilación de dos lignosulfonatos disponibles en el mercado con el objetivo de evaluar su potencial uso como reemplazo de P en la síntesis de resinas de PF.Item Empleo de Macropartículas de quitosano entrecruzadas con TPP como refuerzo en resinas epoxi basadas en DGEBA(Secyt UTN Facultad Regional San Francisco, 2019-10) Ruiz Miraglio, Sofía; Taverna, María E.; Busatto, Carlos Alberto; Helbling, I.; Estenoz, Diana; Nicolau, Verónica V.Las resinas epoxi son materiales poliméricos, que presentan en su estructura uno o más anillos conocidos como epoxi, epóxido, u oxirano. Más del 75% del volumen de ventas de resinas epoxi corresponde a las derivadas bifuncionales del diglicidil éter de bisfenol A (DGEBA). Estas resinas poseen excelente adhesividad, poder aislante, resistencia mecánica, térmica, y a solventes. En este trabajo se obtuvieron y caracterizaron micropartículas de quitosano entrecruzadas con tripolifosfato de sodio (TPP) para su empleo en la obtención de resinas basadas en DGEBA curadas con mezclas de poliamidas.Item Estudio experimental de la hidroximetilación del lignosulfonato de sodio proveniente de Eucalyptus grandis destinado a la modificación de resoles(2015-10-20) Taverna, María E.; Nicolau, Verónica V.; Estenoz, Diana; Meira, Gregorio; XI Simposio Argentino de Polímeros - SAP 2015Las ligninas son polímeros naturales renovables que provienen en su mayoría de desechos de la industria papelera. Debido a sus características estructurales similares al fenol (derivado del petróleo, de importación en Argentina, de costo elevado y alta toxicidad) constituye una muy buena alternativa para su reemplazo en la síntesis de resinas de fenol-formaldehído. Sin embargo, las ligninas presentan baja reactividad, reportándose porcentajes de reemplazo de hasta el 20%m/m en resinas de fenol-formaldehído.1,2 A fin de incrementar la reactividad, se han estudiado varios métodos siendo la metilolación la más importante en resoles.3 En este trabajo, se buscaron las mejores condiciones de reacción (relación inicial %m/m de formaldehído/lignina, temperatura, pH) para la hidroximetilación de un lignosulfonato de sodio comercial. El seguimiento de la reacción se realizó mediante una técnica espectroscópica modificada. Los resultados mostraron muy buena concordancia con el consumo de formaldehído medido volumétricamente.Item Estudio teórico y experimental de la síntesis de resinas de urea-formaldehído(Simposio Argentino de Polímeros, 2015-10-20) Caula, María Andrea; Nicolau, Verónica V.; Estenoz, DianaSe estudió teórica y experimentalmente la hidroximetilación-condensación de la urea a pH=9 y temperaturas 38ºC, 48 ºC, 60 ºC, 70 ºC y 90 ºC para sistemas diluidos homogéneos. Para el seguimiento de la reacción se usaron técnicas volumétricas, cromatográficas, y espectroscópicas. Se desarrolló un modelo matemático que permite simular la hidroximetilación-condensación de la urea considerando las siguientes reacciones secundarias del formaldehído: hidratación/deshidratación y formación de poli(oximetilenglicol). El modelo fue ajustado y validado a partir de las mediciones. Los resultados teóricos mostraron muy buena concordancia con las mediciones.Item Hydroxymethylation of technical lignins from south-american sources with potential use in phenolic resins.(2019-02-16) Taverna, María E.; Estenoz, Diana; Nicolau, Verónica V.; Felissia, Fernando; Area, María CristinaThis work investigates the valorization of sodium lignosulfonate, kraft, and organosolv lignins from South America. A detailed characterization of the lignins and their chemical modification by hydroxymethylation, a reaction between lignin and formaldehyde, were performed. The characterization included measurements of moisture, ash, and carbohydrate contents, elemental and thermogravimetric analysis (TGA), and functional groups and molar mass distributions by Fourier transform infrared spectroscopy (FTIR) and size exclusion chromatography (SEC), respectively. Also, reactive aromatic hydrogens (—HAr) were quantified by the measurement of phenolic hydroxyl groups (P-OH) content by UV-Vis spectroscopy. The different initial formaldehyde/lignin weight ratios (0.07, 1.47), temperatures (40 ºC, 50 ºC, 70 ºC) and pHs (9, 11); and the following of hydroxymethylation reactions by UV-Vis spectroscopy were investigated. All lignins resulted attractive for the use as replacement of phenol in phenolic resins but sodium lignosulfonate was the most appropriate due to its water solubility.Item Lignin-based polyethylene films with enhanced thermal, opacity and biodegradability properties for agricultural mulch applications(2020-09) Chiappero, Lucio Rafael; Bartolomei, Suellen S.; Estenoz, Diana; Moura, E. B.; Nicolau, Verónica V.Lignins are promising alternative raw materials for biocomposites due to their renewability, low cost and abundance. In this work, the use of (softwood and hardwood) Kraft lignins in the development of LLDPE/lignin films for agricultural mulch applications is studied. Processable blends were obtained from unmodified softwood lignin (SW) and from hardwood lignin modified by esterification (HWE). LLDPE was pelletized with (2.5%, 5% and 10%) lignin with particle size between 38 and 75 μm and flexible films were blown extruded. Processable extrusion blends showed temperature differences lower than 20 °C between the Tg of lignin and the melting temperature of LLPDE. Films from neat LLPDE and with 2.5% of HWE and up to 5% SW exhibited statistically comparable (≅ 349%) values of ductility. Ester groups present in lignin improve weight loss of lignin-based blends after soil buried test.Item Mathematical modeling of urea-formaldehyde resins: specific acid-base catalysis(2018-11-06) Caula, María Andrea; Nicolau, Verónica V.; Estenoz, DianaUrea formaldehyde (U-F) base resins are obtained by reaction between urea (U) and formaldehyde (F) and are used mainly as adhesives in the manufacture of wood panels.Item Mechanical evaluation of laminates based on phenolic resins using lignins as partial substitutes for phenol(Bioresources, 2015-10-28) Taverna, María E.; Ollearo, Rocío; Morán, Juan; Nicolau, Verónica V.; Estenoz, Diana; Frontini, PatriciaReducing the consumption of phenol during synthesis of phenolic resins is of great technological and scientific interest because of its economic and environmental implications. In this work, the use of hydroxymethylated lignins as a partial replacement for phenol in resol phenol-formaldehyde resins used for the production of decorative laminates was experimentally studied. The work involved: i) the industrial synthesis of traditional and modified resols with 10%w/w of sodium lignosulfonate and kraft-type lignin; ii) the industrial impregnation of kraft-type paper with the produced resins; iii) the production of laminates on both laboratory and industrial scales; and iv) the measurement of their final properties. The mechanical performance of the laminates was evaluated via the determination of the Young modulus, bending strength, biaxial impact strength, and Mode-I interlaminar fracture toughness. The (modified and traditional) laminates exhibited statistically significant differences in mechanical properties. However, the partial lignin replacement did not produce effects that were detrimental effects to the overall performance of the decorative laminates.Item Microparticles based on ionic and organosolv lignins for the controlled release of atrazine(Journal of Hazaourdos Materials, 2018-07-02) Taverna, María E.; Busatto, Carlos Alberto; Lescano, Maia Raquel; Nicolau, Verónica V.; Zalazar, Cristina; Meira, Gregorio; Estenoz, DianaLignins are natural polymers of the lignocellulosic biomass. Nowadays, there is a growing interest in developing value-added products based on lignins due to their renewability, low cost and abundance. In this work, lignin microspheres from organosolv and ionic isolation processes were prepared for the controlled release of atrazine. Microspheres were prepared by the solvent extraction/evaporation technique. The controlled release of atrazine from organosolv and ionic lignins microparticles was studied in water. Mobility experiments were performed in an agricultural soil from Argentina. The results showed that microparticles prepared using dichloromethane as the dispersed phase were spherical, while lignins dispersed in ethyl acetate produce irregular microparticles. Organosolv lignin microparticles presented higher encapsulation efficiency for all herbicide loads. About 98% and 95% of atrazine was released in 24 and 48h approximately from organosolv and ionic lignin microparticles, respectively. The release profiles of atrazine from both lignin microparticles were not affected by the herbicide load. Atrazine mobility experiments in soil showed that about 80% of free atrazine was leached in 37 days, while 65.0% and 59.7% of the herbicide was leached from ionic and organosolv lignin microparticles, respectively. Thus, atrazine-loaded microparticles could reduce leaching compared to a commercial formulation of free atrazine.Item Morphology modulation of silica mesoporous nano- and microparticles for atrazine - controlled release(2022-06-09) Fookes, Federico A.; Busatto, Carlos Alberto; Taverna, María E.; Casis, Natalia; Lescano, Maia Raquel; Estenoz, DianaAtrazine is a moderately toxic triazine, used as a selective pre- and post-emergence herbicide. After application, it remains in the environment due to its low biodegradability causing severe environmental effects. Several controlled release systems have been proposed in order to minimize the negative impact of the herbicide on the environment. In particular, mesoporous silica nanoparticles have shown great potential in the agricultural area due to their controlled size and porosity, high surface area and non-toxicity. In this work, silica nano- and microparticles were synthesized and evaluated as atrazine delivery systems. The morphology and size distribution of the particles were characterized using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The release profiles were studied by in vitro assays in water. In addition, phytotoxicity tests were performed using Lactuca sativa seeds. The mesoporous nano- and microparticles exhibited sustained release for at least 24 h and reduced phytotoxicity compared to free atrazine.Item On the use of espina corona gum as a polymeric additive in water-based drilling fluid(2022-06-26) Villada, Yurany A.; Taverna, María E.; Maffi, Juan M.; Gilleta, Sebastián; Casis, Natalia; Estenoz, DianaThe aim of this work is to evaluate the espina corona gum (ECG) as a sustainable viscosifier or filtration reducer additive in water-based drilling fluids (WBMs) as a potential replacement of guar gum (GG). ECG is a galactomannan isolated from leguminous seeds of Gleditsia amorphoides, trees that grow in South America with viscosifier properties and applications in the food area. ECG was characterized by FTIR, Z potential, intrinsic viscometry, TGA, and steady and oscillatory shear rheological analysis. Moreover, its effect on the main functional properties of WBMs was studied. Fluids containing bentonite (BT), polyanionic cellulose (PAC), GG or ECG were prepared, and rheological, filtration, thermal and structural properties were determined. In order to study the theoretical rheological behavior, several models such as power law, Sisko and Herschel-Bulkley were evaluated. The rheological studies revealed that WBMs containing ECG exhibit higher viscosities in comparison with those with GG. Herschel-Bulkley parameters indicated that the WBMs with high ECG concentration showed higher yield stress. In addition, the presence of ECG improves the thermal stability and filtration properties. The results indicate that ECG can be considered as an innovative, renewable and non-toxic alternative to partially or totally replace GG in WBMs.