Improved xylitol production from olive stones hydrolysates by biological detoxification

Olive stones, currently used as a biosource of heat and power, is gaining research interest as a feedstock for a biorefinery based on olive derived wastes. In this work, pure xylitol crystals were obtained and fully characterized as one of the possibilities of taking full advantage of this by-product of olive oil production. The proposed process includes a two-step pretreatment (water and acid extractions), detoxification of the liquid fractions and fermentation of sugars. After the water extraction, a liquid fraction with antioxidant capacity was recovered; the second step was done with dilute sulfuric acid for solubilization of sugars, resulting in a solution containing more than 60 g/l of xylose as the main sugar. This liquor contained also up to 16 g/l acetic acid, which rendered it not fermentable. Also other compounds, potentially inhibitors in downstream operations, were produced during the pretreatment, requiring a detoxification procedure. In this work, a chemical-free, biological treatment with Saccharomyces cerevisiae proved to be the best detoxification method, as glucose, furfural, hydroxymethylfurfural and acetic acid were consumed. The subsequent inoculation of Candida boidinii produced xylitol concentrations above 38 g/l after 90h fermentation time and a yield as high as 63%, equivalent to 12 g xylitol/100 g olive stones

Inhibition of Pichia stipitis fermentation of hydrolysates from olive tree cuttings

The ethanolic fermentation of liquid fractions (hydrolysates) issued from dilute acid pre-treatment of olive tree biomass by Pichia stipitis is reported for the first time. On the one side, P. stipitis has been reported as the most promising naturally occurring C5 fermenting microorganism; on the other side, olive tree biomass is a renewable, low cost, and lacking of alternatives agricultural residue especially abundant in Mediterranean countries. The study was performed in two steps. First, the fermentation performance of P. stipitis was evaluated on a fermentation medium also containing the main inhibitors found in these hydrolysates (acetic acid, formic acid, and furfural), as well as glucose and xylose as carbon sources. The effect of inhibitors, individually or in a mixture, on kinetic and yield parameters was calculated. In a second step, hydrolysates obtained from 1% (w/w) sulfuric acid pre-treatment of olive tree biomass at 190ºC for 10 min were used as a real fermentation medium with the same microorganism. Due to inhibition, effective fermentation required dilution of the hydrolysate and either overliming or activated charcoal treatment. Results show that ethanol yields obtained from hydrolysates, ranging from 0.35 to 0.42 g/g, are similar to those from synthetic medium, although the process proceeds at lower rates. Inhibiting compounds affect the fermentation performance in a synergistic way. Furfural is rapidly assimilated by the yeast; acetic acid and formic acid concentrations decrease slowly during the process. Activated charcoal or overliming detoxification improve the fermentability of diluted hydrolysates

Hydrothermal pre-treatment of rapeseed straw

As a first step for ethanol production from alternative raw materials, rapeseed straw was studied for fermentable sugar production. Liquid hot water was used as a pre-treatment method and the influence of the main pre-treatment variables was assessed. Experimental design and response surface methodology were applied using pretreatment temperature and process time as factors. The pretreated solids were further submitted to enzymatic hydrolysis and the corresponding yields were used as pretreatment performance evaluation. Liquid fractions obtained from pre-treatment were also characterized in terms of sugars and no-sugar composition. A mathematical model describing pre-treatment effects is proposed. Results show that enzymatic hydrolysis yields near to 100% based on pretreated materials can be achieved at 210-220ºC for 30-50 min, equivalent to near 70% of glucose present in the raw material. According to the mathematical model, a softer pre-treatment at 193ºC for 27 min results in 65% of glucose and 39% of xylose available for fermentation

Dilute acid pre-treatment of rapeseed straw for fermentable sugar generation

The influence of the main pretreatment variables on fermentable sugar generation from rapeseed straw is studied using an experimental design approach. Low and high levels for pretreatment temperature (140–200 ºC), process time (0–20 min) and concentration of sulfuric acid (0.5–2% w/v) were selected according to previous results. Glucose and xylose composition, as well as sugar degradation, were monitored and adjusted to a quadratic model. Non-sugar components of the hydrolysates were also determined. Enzymatic hydrolysis yields were used for assessing pretreatment performance. Optimization based on the mathematical model show that total conversion of cellulose from pretreated solids can be achieved at pretreatment conditions of 200 ºC for 27 min and 0.40% free acid concentration. If optimization criteria were based on maximization of hemicellulosic sugars recovery in the hydrolysate along with cellulose preservation in the pretreated solids, milder pretreatment conditions of 144 ºC, 6 min and 2% free acid concentration should be used

Hemicellulose-derived sugars solubilisation of rape straw. Cofermentation of pentoses and hexoses by Escherichia coli

Bioconversion of hemicellulose sugars is essential for increasing fuel ethanol yields from lignocellulosic biomass. We report for the first time with rape straw, bioethanol production from hemicellulose sugars. Rape straw was pretreated at mild conditions with sulfuric acid to solubilize the hemicellulose fraction. This pretreatment allows obtaining a prehydrolysate, consisting basically in a solution of monomeric hemicellulosic sugars, with low inhibitor concentrations. The remaining water insoluble solid constitutes a cellulose-enriched, free of extractives material. The influence of temperature (120ºC and 130ºC), acid concentration (2-4% w/v) and pretreatment time (30-180 min) on hemicellulose-derived sugars solubilisation was evaluated. The highest hemicellulosic sugars recovery, 72.3%, was achieved at 130ºC with 2% sulfuric acid and 60 min. At these conditions, a concentrated sugars solution, 52.4 g/L, was obtained after three acid consecutive contacts, with 67% xylose and acetic acid concentration above 4.5 g/L. After a detoxification step by activated charcoal or ion-exchange resin, prehydrolysate was fermented by ethanologenic Escherichia coli. An alcoholic solution of 25 g/L and 86% of theoretical ethanol yield was attained after 144 h when the prehydrolysate was detoxified by ion-exchange resin. The results obtained in the present work show sulfuric acid pretreatment under mild conditions and E. coli as an interesting process to exploit hemicellulosic sugars in rape straw

A new improved database to support spanish phenological observations

Póster presentado en: EGU General Assembly celebrada del 23 al 28 de abril de 2017 en Viena, Austria

Adaptation and Validation of the Sexting Behaviors Scale to Adolescents (ECS)

El aumento de la preocupación social en nuestro país por los fenómenos relacionados con el mal uso de la conectividad móvil por parte de los adolescentes, ha incremento el interés por conocer de forma más exhaustiva este tipo de manifestaciones. En el caso del sexting, no contamos con instrumentos de medida estandarizados en castellano que permitan una aproximación más rigurosa a las variables que están determinando este tipo de conductas, por ello el objetivo de este estudio ha sido la adaptación y validación de la Sexting Behaviors Scale (SBS), con una muestra de 765 adolescentes españoles. Previamente, se realizó un primer estudio piloto con 104 sujetos que sirvió para acometer los primeros ajustes y modificaciones a la escala. Los resultados obtenidos con los análisis estadísticos, tanto de tipo exploratorio como confirmatorio, permiten concluir que la Escala de Conductas sobre Sexting (ECS) es un instrumento con evidencias contrastadas de fiabilidad y validez.The increase of the social concern in our country by the phenomena related to the improper use of mobile connectivity by the adolescents, has increased the interest in knowing more comprehensively this type of manifestations. In the case of sexting, we do not have standardized measurement instruments in Spanish that allow a more rigorous approach to the variables that are determining this type of behavior, therefore, the aim of this study has been the adaptation and validation of the Sexting Behaviors Scale (SBS), with a sample of 765 Spanish adolescents. Previously, pilot study was carried out with 104 subjects who served to undertake the first adjustments and modifications to the scale. The results obtained with the statistical analysis, both exploratory and confirmatory, allow to conclude that the Escala de Conductas sobre Sexting (ECS) is an instrument with proven evidence of reliability and validity

Adaptación y validación de la escala de conductas sobre sexting para adolescentes (ECS)

Resumen:El aumento de la preocupación social en nuestro país por los fenómenos relacionados con el mal uso de la conectividad móvil por parte de los adolescentes, ha incremento el interés por conocer de forma más exhaustiva este tipo de manifestaciones. En el caso del sexting, no contamos con instrumentos de medida estandarizados en castellano que permitan una aproximación más rigurosa a las variables que están determinando este tipo de conductas, por ello el objetivo de este estudio ha sido la adaptación y validación de la Sexting Behaviors Scale (SBS), con una muestra de 765 adolescentes españoles. Previamente, se realizó un primer estudio piloto con 104 sujetos que sirvió para acometer los primeros ajustes y modificaciones a la escala. Los resultados obtenidos con los análisis estadísticos, tanto de tipo exploratorio como confirmatorio, permiten concluir que la Escala de Conductas sobre Sexting (ECS) es un instrumento con evidencias contrastadas de fiabilidad y validez. Abstract:The increase of the social concern in our country by the phenomena related to the improper use of mobile connectivity by the adolescents, has increased the interest in knowing more comprehensively this type of manifestations. In the case of sexting, we do not have standardized measurement instruments in Spanish that allow a more rigorous approach to the variables that are determining this type of behavior, therefore, the aim of this study has been the adaptation and validation of the Sexting Behaviors Scale (SBS), with a sample of 765 Spanish adolescents. Previously, pilot study was carried out with 104 subjects who served to undertake the first adjustments and modifications to the scale. The results obtained with the statistical analysis, both exploratory and confirmatory, allow to conclude that the Escala de Conductas sobre Sexting (ECS) is an instrument with proven evidence of reliability and validity

Construcción y validación de la escala de conductas sobre sexting (ECS)

ABSTRACTThe aim of this paper was to construct and validate the Escala de Conductas sobre Sexting (ECS) (by the absence of standardized procedures for evaluating behaviors related to the sending and receiving sexts -text messages or images with provocative or sexual content- through the mobile phone and social networks) (Dir, Cyders y Coskunpinar, 2013), with a sample of 985 Spanish university students. Firstly, a pilot study was made with 110 university students, showing a good internal consistency (α = .923) and allowing to execute the initial adjustments and modifications. To confirm the relationship between the items, the sample, randomly selected, was divided into two. An exploratory factorial analysis, with Varimax rotation in the first subsample, showed a significant relationship between the items and a good internal consistency (α = .922), retaining three factors that explained the 66.406% of the variance. Finally, a confirmatory factorial analysis carried out with the second subsample, revealed a good fit of the model. On the other hand, the Goodness of Fit Index (GFI) and the Adjusted Goodness of Fit Index (AGFI) offered values of .919 and .854, respectively; while the average of the Root Mean Square Error of Approximation (RMSEA) showed a value of .061. All these data lead to the conclusion that the ECS seems to be a valid and reliable scale to evaluate the sexting behaviors in this population.RESUMENEl objetivo de este estudio ha sido la construcción y validación de la Escala de Conductas sobre Sexting (ECS) (ante la ausencia de procedimientos estandarizados que permitan evaluar conductas relacionadas con el envío y recepción de sexts -mensajes de texto o imágenes con contenido provocativo o sexual- a través del teléfono móvil y de las redes sociales) (Dir, Cyders y Coskunpinar, 2013), en una muestra de 985 universitarios españoles. En primer lugar se realizó un estudio piloto con 110 estudiantes mostrando buena consistencia interna (α = .923) y permitiendo efectuar los primeros ajustes y modificaciones a la escala. Para confirmar la relación entre los ítems, se procedió a dividir la muestra, seleccionada aleatoriamente, en dos. Un análisis factorial exploratorio, con rotación Varimax sobre la primera submuestra, mostró una relación significativa entre los ítems con una consistencia interna adecuada (α = .922), reteniendo tres factores que explican el 66.406% de la varianza. Finalmente se comprobó la validez de constructo mediante un análisis factorial confirmatorio sobre la segunda submuestra, que reveló buen ajuste del modelo. Por otro lado, el índice de bondad de ajuste (GFI) y el corregido (AGFI) ofrecieron valores de .919 y .854, respectivamente, mientras que el promedio de los residuales estandarizados (RMSEA) arrojó un valor de .061.  Estos datos permiten concluir que la escala construida (ECS) parece ser un instrumento válido y fiable para evaluar las conductas de sexting en esta población.ABSTRACTThe aim of this paper was to construct and validate the Escala de Conductas sobre Sexting (ECS) (by the absence of standardized procedures for evaluating behaviors related to the sending and receiving sexts -text messages or images with provocative or sexual content- through the mobile phone and social networks) (Dir, Cyders y Coskunpinar, 2013), with a sample of 985 Spanish university students. Firstly, a pilot study was made with 110 university students, showing a good internal consistency (α = .923) and allowing to execute the initial adjustments and modifications. To confirm the relationship between the items, the sample, randomly selected, was divided into two. An exploratory factorial analysis, with Varimax rotation in the first subsample, showed a significant relationship between the items and a good internal consistency (α = .922), retaining three factors that explained the 66.406% of the variance. Finally, a confirmatory factorial analysis carried out with the second subsample, revealed a good fit of the model. On the other hand, the Goodness of Fit Index (GFI) and the Adjusted Goodness of Fit Index (AGFI) offered values of .919 and .854, respectively; while the average of the Root Mean Square Error of Approximation (RMSEA) showed a value of .061. All these data lead to the conclusion that the ECS seems to be a valid and reliable scale to evaluate the sexting behaviors in this population