• Energy Research

Ce travail propose une combinaison séquentielle d'explosion de vapeur et de délignification organosolv pour le fractionnement de Pinus radiata. Un prétraitement efficace pour optimiser pleinement l'utilisation des matériaux lignocellulosiques est la clé pour rentabiliser une bioraffinerie, en particulier pour les bois résineux, connus pour être plus récalcitrants que les autres matières premières lignocellulosiques. L'explosion de vapeur a un double effet sur la biomasse à mesure que des changements morphologiques et chimiques sont introduits. Une étape de délignification a été déclarée nécessaire afin de faciliter l'accessibilité des enzymes hydrolytiques à la cellulose tout en évitant les liaisons non productives avec la lignine présente. Trois conditions dâ € ™ explosion de vapeur ont à © tà © testà © es (170°C, 5 min ; 180°C, 10 min ; 170°C, 5+5 min) suivies dâ € ™ une à © tape de dà © lignification dâ € ™ organosolv, rà © alisà © e dans deux conditions diffà © rentes (170°C, 60 min ; 170°C, 90 min). Tous les rendements de traitement, l'étendue de la délignification et les rendements d'hydrolyse ont été déterminés pour évaluer chaque étape. Le traitement par explosion de vapeur n'a pas produit d'étendue de délignification élevée. La délignification globale maximale (50,4 %) a été obtenue en combinant l'explosion de vapeur à deux cycles avec les conditions de post-traitement les plus sévères testées. L'hydrolyse enzymatique du résidu cellulosique s'est améliorée après délignification organosolv ; cependant, les rendements d'hydrolyse n'ont pas dépassé 35%. Les changements chimiques subis par les lignines de résineux sont probablement responsables de la faible digestibilité. Este trabajo propone una combinación secuencial de explosión de vapor y deslignificación organosolv para el fraccionamiento de Pinus radiata. Un pretratamiento eficiente para optimizar al máximo el uso de materiales lignocelulósicos es la clave para rentabilizar una biorrefinería, especialmente para maderas blandas, conocidas por ser más recalcitrantes que otras materias primas lignocelulósicas. La explosión de vapor tiene un doble efecto sobre la biomasa a medida que se introducen cambios morfológicos y químicos. Se ha indicado que es necesaria una etapa de deslignificación para facilitar la accesibilidad de las enzimas hidrolíticas a la celulosa, evitando al mismo tiempo los enlaces no productivos con la lignina presente. Se probaron tres condiciones de explosión de vapor (170°C, 5 min; 180°C, 10 min; 170°C, 5+5 min) seguidas de una etapa de deslignificación organosolv, llevada a cabo en dos condiciones diferentes (170°C, 60 min; 170°C, 90 min). Se determinaron todos los rendimientos de tratamiento, el grado de deslignificación y los rendimientos de hidrólisis para evaluar cada etapa. El tratamiento de explosión de vapor no produjo un alto grado de deslignificación. La deslignificación global máxima (50,4%) se logró al combinar la explosión de vapor de dos ciclos con la condición de postratamiento más severa probada. La hidrólisis enzimática del residuo celulósico mejoró después de la deslignificación con organosolv; sin embargo, los rendimientos de la hidrólisis no superaron el 35%. Los cambios químicos sufridos por las ligninas de madera blanda son presumiblemente responsables de la baja digestibilidad. This work proposes a sequential combination of steam explosion and organosolv delignification for Pinus radiata fractionation. An efficient pretreatment to fully optimize the use of lignocellulosic materials is the key to make a biorefinery profitable, especially for softwoods, known to be more recalcitrant than other lignocellulosic raw materials. Steam explosion has a dual effect on biomass as morphological and chemical changes are introduced. A delignifying stage has been stated to be necessary in order to ease hydrolytic enzymes accessibility to cellulose while avoiding non-productive bonds with the lignin present. Three steam explosion conditions were tested (170°C, 5 min; 180°C, 10 min; 170°C, 5+5 min) followed by an organosolv delignification stage, carried out at two different conditions (170°C, 60 min; 170°C, 90 min). All treatment yields, delignification extent, and hydrolysis yields were determined to evaluate each stage. The steam explosion treatment did not produce high delignification extent. Maximum global delignification (50,4%) was achieved when combining the two-cycle steam explosion with the most severe post-treatment condition tested. Enzymatic hydrolysis of the cellulosic residue improved after organosolv delignification; however, hydrolysis yields did not exceed 35%. The chemical changes undergone by softwood lignins are presumably responsible for the low digestibility. يقترح هذا العمل مزيجًا متسلسلًا من انفجار البخار وتفكيك المذيب العضوي لتجزئة الصنوبر المشع. المعالجة المسبقة الفعالة لتحسين استخدام المواد الليجنوسليلوزية بشكل كامل هي المفتاح لجعل التكرير الحيوي مربحًا، خاصة بالنسبة للخشب اللين، المعروف بأنه أكثر تمردًا من المواد الخام الليجنوسليلوزية الأخرى. الانفجار البخاري له تأثير مزدوج على الكتلة الحيوية حيث يتم إدخال تغييرات مورفولوجية وكيميائية. وقد ذُكر أن مرحلة التفكيك ضرورية من أجل تسهيل وصول الإنزيمات المائية إلى السليلوز مع تجنب الروابط غير المنتجة مع وجود اللجنين. تم اختبار ثلاث ظروف للانفجار البخاري (170 درجة مئوية، 5 دقائق ؛ 180درجة مئوية، 10 دقائق ؛ 170 درجة مئوية، 5+ 5 دقائق) تليها مرحلة تفريغ الذوبان العضوي، التي تتم في حالتين مختلفتين (170 درجة مئوية، 60 دقيقة ؛ 170 درجة مئوية، 90 دقيقة). تم تحديد جميع نتائج المعالجة، ومدى إزالة الترميز، ونتائج التحلل المائي لتقييم كل مرحلة. لم تنتج معالجة الانفجار البخاري درجة عالية من التفكيك. تم تحقيق أقصى قدر من التفكيك العالمي (50.4 ٪) عند الجمع بين انفجار البخار ثنائي الدورة وأشد حالة ما بعد المعالجة تم اختبارها. تحسنت التحلل المائي الأنزيمي لبقايا السليلوز بعد إزالة الترميز العضوي ؛ ومع ذلك، لم تتجاوز غلة التحلل المائي 35 ٪. من المفترض أن تكون التغيرات الكيميائية التي يمر بها اللجنين اللين مسؤولة عن انخفاض قابلية الهضم.

The inhibition of the enzymatic saccharification of acid pretreated corn stover (PCS) biomass due to several compounds either present in PCS or produced during saccharification has been studied. The prospective inhibitors tested were glucose (≤110�g�L−1), celobiose (≤24�g�L−1), xylose (≤50�g�L−1), arabinose (≤1.5�g�L−1), furfural (≤2�g�L−1), hydroxymethylfurfural (≤1�g�L−1), acetic acid (≤4�g�L−1), and lignin (≤50�g�L−1). Each of these compounds was added at three different concentrations, being the concentration intervals different according to standard maximum concentrations of such compounds in the reaction medium, previously measured and described in literature. In addition, these experiments were employed to evaluate the standard error present during the evaluation of the results obtained in the inhibition reactions. Those results show that significant inhibition was only detected for lignin (more than 25�g�L−1) and it was also appreciable for glucose at high concentrations (above 75�g�L−1), although it was not remarkable at medium concentrations (40�g�L−1). On the other hand, neither of the remaining compounds tested presented any significant inhibitory effect at the usual process concentration range. � 2017 Elsevier Ltd

Eucalyptus globulus woodchips were subjected to steam explosion under a variety of operational conditions in order to evaluate their effect on a subsequent enzymatic hydrolysis. Steam explosion enhanced the enzymatic hydrolysis of the solid fraction. The application of a laccase-mediator system (LMS) before the enzymatic hydrolysis increased the glucose yield from 24.7 to 27.1%, probably as a result of the detoxification of the substrate. However, when xylanase was used to boost the LMS treatment, the hydrolysis rates did not improve. In order to assess the total amount of sugars obtainable from E. globulus, the liquid fraction obtained from the steam explosion was subjected to hydrolysis too. The enzymatic hydrolysis of the liquid fraction was more efficient than the acid hydrolysis, breaking down 82.7% of the xylooligosaccharide backbone into its monomeric constituent, xylose. The overall yield was 210. g of sugars per kg of raw material. © 2012 Elsevier Ltd.

The stabilization effects on a novel commercial β-glucosidase preparation from Aspergillus fumigatus during saccharification of ethanol-water pretreated wheat straw were analysed in comparison to this enzyme stability during cellobiose hydrolysis. For this purpose, the kinetics of β-glucosidase residual activity during cellobiose hydrolysis from 40 till 70 °C were studied, resulting in the fitting of a first-order partial deactivation model. Furthermore, a subsequent fitting of a kinetic model including this first-order deactivation equation and a Michaelis-Menten equation with double competitive inhibition by glucose and uncompetitive inhibition by cellobiose to released glucose was successful. Finally, global enzyme deactivation and prospective deactivation of enzyme remaining in the liquid phase were evaluated during wheat straw hydrolysis at 50 °C as a relevant saccharification process. Results suggest that the presence of a solid substrate dramatically reduces the global deactivation rate of the enzyme and, in addition, there is no loss the stability of the enzyme in the liquid phase along the saccharification process, even for 72 h.

The effect of fluid dynamic conditions on enzymatic hydrolysis of acid pretreated corn stover (PCS) has been assessed. Runs were performed in stirred tanks at several stirrer speed values, under typical conditions of temperature (50°C), pH (4.8) and solid charge (20% w/w). A complex mixture of cellulases, xylanases and mannanases was employed for PCS saccharification. At low stirring speeds (<150rpm), estimated mass transfer coefficients and rates, when compared to chemical hydrolysis rates, lead to results that clearly show low mass transfer rates, being this phenomenon the controlling step of the overall process rate. However, for stirrer speed from 300rpm upwards, the overall process rate is controlled by hydrolysis reactions. The ratio between mass transfer and overall chemical reaction rates changes with time depending on the conditions of each run.

Bacterial cellulose (BC) synthesized by Gluconacetobacter sucrofermentans CECT 7291 seems to be a good option for the restoration of degraded paper. In this work BC layers are cultivated and purified by two different methods: an alkaline treatment when the culture media contains ethanol and a thermal treatment if the media is free from ethanol. The main goal of these tests was the characterization of BC layers measured in terms of tear and burst indexes, optical properties, SEM, X-ray diffraction, FTIR, degree of polymerization, static and dynamic contact angles, and mercury intrusion porosimetry. The BC layers were also evaluated in the same terms after an aging treatment. Results showed that BC has got high crystallinity index, low internal porosity, good mechanical properties and high stability over time, especially when purified by the alkaline treatment. These features make BC an adequate candidate for degraded paper reinforcement.