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Totora (Schoenoplectus californicus (C.A. Mey.) Soják) is a sedge that grows in lakes and marshes in America and some of the Pacific Islands. The hypothesis tested was that the rind and pith of totora stems have different chemical characteristics. A higher ash content on the pith (7.81% vs. 6.36%) may indicate strategies of the plant to reinforce the aerenchyma tissue and clarify the storage mechanism of compounds by bio mineralization. Almost double acid-insoluble lignin content in the rind (16.42% vs. 8.90%) may indicate the potential optimization of industrial procedures such as paper production by using specific tissues of the plant. [ABSTRACT FROM AUTHOR]

Steam explosion and steam pre-treatment have proved capable of enhancing enzymatic saccharification of lignocellulosic materials. However, until now, these methods had not been compared under the same operational conditions and using the same raw material. Both pre-treatments lead to increased yields in the saccharification of Eucalyptus globulus; but results have been better with steam pre-treatments, despite the more accessible surface of exploded samples. The reason for this finding could be enzymatic inhibition: steam explosion causes a more extensive extraction of hemicelluloses and releases a greater amount of degradation products which can inhibit enzymatic action. Enzymatic inhibition is also dependent on the amount and chemical structure of lignin, which was also a contributing factor to the lower enzymatic yields obtained with the most severe pre-treatment. Thus, the highest yields (46.7% glucose and 73.4% xylose yields) were obtained after two cycle of steam treatment, of 5 and 3 min, at 183 °C. [ABSTRACT FROM AUTHOR]

The fractionation of wheat straw by ethanol-water (EW) pre-treatment was studied regarding its main operating conditions: time, temperature, L/S ratio and ethanol percentage were optimized by using an orthogonal experimental design (Taguchi). Afterwards, diluted sulfuric acid (DSA) hydrolysis and EW treatments have been compared in terms of energy consumption and yield of a cellulosic solid residue able to be enzymatically hydrolyzed to glucose. Experimental results show that temperature is the only variable of EW with a significant effect on the quality of the pretreated solids. EW pre-treatment of wheat straw is more effective than DSA hydrolysis due to its higher capacity of delignification. Moreover, a high glucose yield (80%) can be obtained by enzymatic hydrolysis of a solid pretreated with a moderate energy input EW (160 °C, 45 min) while wheat straw needs of a higher energy input during DSA to produce a similar yield of glucose after saccharification. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Cardoon (Cynara cardunculus) stalks were submitted to steam explosion (183 °C, 5 min) with a yield of 88% and a lignin loss of around 7%. Cardoon (C) and steam exploded cardoon (CSE) were characterized by wet chemical analysis and Py-GC/MS. Total lignin and its S/G ratio were 21.6% and 1.35 in C and 22.4% and 1.40 in CSE. These samples were delignified by kraft and organosolv processes. Cardoon pulps were obtained with different yields of 45.1% for kraft and 61.2% for organosolv. Kraft pulps yields were 45.1% and 50.9%, respectively, for Ck and CSE-K, corresponding to a lignin loss of 74.7% and 72.2%. The S/G ratio was similar 1.25 and 1.23. Organosolv pulps presented higher yields (61.2% vs 73.3%) and were less delignified (30.5% vs 13.8%), and the S/G ratio was 1.54 and 1.47, respectively, for Corg and CSE-org. Overall, the condition chosen for steam explosion allowed a low mass loss but did not promote delignification and neither enhanced lignin removal during kraft and organosolv processes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Steam explosion and steam pre-treatments were carried out before kraft pulping. [•] The rate of extraction of hemicelluloses was similar with both pre-treatments. [•] Steam explosion enhanced delignification more efficiently. [•] Pre-treatments reduced paper mechanical properties owing to the fiber morphology. [•] Paper optical properties were boosted when pre-treatments were carried out. [ABSTRACT FROM AUTHOR]

This study evaluates the use of steam explosion (SE) as a pre-treatment of Eucalyptus globulus chips, aimed at making this wood suitable as feedstock in biorefineries or alternative processes such as biopulping. Several SE treatments were applied, modifying the following variables: previous hydration of the chips, number of SE cycles, and duration of the first cycle. Chemical composition and structural properties were analyzed after all treatments. Our results show that acetone and hot water extractives contents increased between 1.0% and 6.2% and between 3.6% and 7.1%, respectively, depending on SE operational conditions. Holocellulose content was also observed to decrease (9.4 to 15.6%), while the Klason lignin underwent a slight solubilization. Furthermore, greater water retention capacity and new bigger sized pores were found in the exploded samples. It is reasonable to expect that these changes would facilitate the subsequent implementation of chemical or biological treatments of the cellulose fraction in the biorefinery design. [ABSTRACT FROM AUTHOR]