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Developing environmentally friendly barrier coatings as an alternative to petroleum-based polymer packaging is a challenge. Cellulose nanofibres (CNF) films have exhibited great potential as water and gas barrier layers. Recycled paper was multi-layer coated with three commercial CNF (mechanical (M-CNF), TEMPO (T-CNF) and carboxymethylated (C-CNF)) using two metering systems (wound rod and blade micrometer) and two drying methods (tension-free contact drying and air drying). The coatability and rheological behaviour of the CNF suspensions were analysed. The gas, water and grease barrier properties of the CNF coated papers were determined and compared with the results of paper coated with cationic starch. The three CNF suspensions and the starch suspension were successfully coated using both metering systems. In the multi-layer coating, air drying yielded higher coat weights than contact drying, and the difference was more noticeable in M-CNF and T-CNF coated samples. A lack of uniformity observed in CNF coatings increased with the number of coating layers. M-CNF coated samples had a whitish surface with a uniform appearance, but coating was insufficiently compact to provide barrier properties. T-CNF coating exhibited a cracked surface and consequently provided no barrier properties. Drying stresses caused breakage of T-CNF coating, which could be explained by the drop in apparent viscosity at much lower rheological shear stresses in the T-CNF suspension. C-CNF showed successful coatability and provided barrier properties to paper with both metering systems and drying methods. Air permeance decreased considerably and the water wettability of the paper decreased by 60% compared to the reference paper, even with a single coating layer (about 1 g·m−2). In addition, a greaseproof paper (grease resistance >1800 s and kit no >10) was obtained with multi-layer C-CNF coating. Although water vapour permeability at 90 % RH and 20 °C decreased slightly with a single layer of CN

A techno-economic study of different pretreatments of lignocellulosic biomass (LCB) has been carried out: diluted sulfuric acid (DSA) pretreatment, fractionation of LCB with an ethanol-water mixture (EW), and the same process with liquor reuse (EWR). A simplified analysis was performed considering selected equipment, utilities, and supplies consumption, while also considering the influence of the liquid to solid (L/S) ratio. The equipment cost was found to be similar for the three alternatives, although selected operating costs were somewhat lower for the DSA pretreatment than for the EW. When liquor reuse was considered, EWR costs were significantly reduced. For the case study of L/S of 10, costs were halved under the tested conditions. The influence of the L/S ratio was found to be approximately linear, and correlations were obtained to estimate steam and utilities consumption for different L/S ratios.

[EN] Washi, or Japanese paper, has been the most widely used documentary heritage restora tion material in the West since 1960s. Currently, Japanese paper is marketed under the basics prin ciples of stability, compatibility and quality, although information on physical-mechanical, chemical properties and their long-term stability is not always available. Therefore, to improve washi knowledge, this study aims to characterize the physical-mechanical, chemical and fibrous properties of four papers commonly used in paper restoration: Sekishu Thin, Kozo Natur, Kuranai and Ohban Bunkamisu. As well as the effect of the application of these as a manual lamination treatment, in two cartographic documents (make by mechanical and chemical pulp) with serious acidity problems, dated in 1924 and 1898 each one. The study determined the grammage, pH value, mineral matter content, tensile strength and elongation, and optical properties of each paper and lining documents with washi, before and after accelerated aging to evaluate the stability of the treatment, [ES] El washi, o papel japonés, es el material de restauración del patrimonio documental y bibliográfico más empleado en Occidente desde la década de 1960. Actualmente, el papel japonés se comercializa bajo los principios básicos de estabilidad, compatibilidad y calidad, aunque no siempre se dispone de información sobre las propiedades físico-mecánicas, químicas y su estabili dad a largo plazo. Por lo tanto, para profundizar el conocimiento sobre el washi, este estudio tiene como objetivo caracterizar las propiedades físico-mecánicas, químicas y fibrosas de cuatro papeles comúnmente utilizados para la restauración de documentos históricos: Sekishu Thin, Kozo Natur, Kuranai y Oh ban Bunkamisu, así como el efecto de la aplicación de estos como tratamiento de laminación ma nual, en dos documentos cartográficos (constituidos por pasta mecánica y química) con graves problemas de acidez, datados en 1924 y 1898. El estudio determinó el gramaje, el pH, el contenido de materia mineral, la resistencia a la tracción y al alargamiento, y las propiedades ópticas de cada papel y de los documentos laminados con el washi, antes y después del envejecimiento acelerado para evaluar la estabilidad del tratamiento

[ES] La presente invención es un procedimiento para la obtención de un papel de embalaje reforzado que comprende la aplicación de un licor residual de pretratamiento de restos lignocelulósicos con alcohol-agua en el papel de embalaje y su posterior secado., [EN] The present invention is a procedure for obtaining a reinforced packaging paper that includes the application of a residual liquor of pretreatment of lignocellulosic remains with alcohol-water in the packaging paper and its subsequent drying.

The evolution of lignocellulosic biorefineries increasing the process complexity and integration through the processing of multiple raw biomass-based materials into several products is described. This critical overview deals with available lignocellulosic feedstocks, pretreatment operations, enzymatic saccharification to monosaccharides and their final transformation into bioethanol and other bio-based products. Aspects as process operating conditions, modes of operation, underlying physical and chemical phenomena, and mathematical modelling are addressed. Pretreatment stage is a key step for any further processing, specially when using multifeedstock. The use of ethanol-water mixtures for biomass fractionation is a promising treatment able to compete with the nowadays more employed pretreatment such as steam explotion and diluted acid processes. Enzymatic saccharification of pretreated biomass has been analysed considering its complexity and selectivity. Its mathematical modelling is described in detail, together with the underlying phenomena, highlighting the importance of mass transfer in a biphasic system. An adequate operation unit design, scale-up and control, and process design and integration can be ensured in this way. Finally, biotransformations of monosaccharides to biofuels and platform chemicals is analysed as they are becoming key processes within bioeconomy, in the framework of integrated biorefinery to fuels, chemicals and materials.

The high humidity produced by the ripening of fruit and vegetables during refrigerated storage and transport leads to a noticeable loss of strength of corrugated board packaging. Increasing use of recycled fibres in the manufacture of corrugated board further reduces box compression strength. Adding virgin fibres to the furnish composition of liner paper could solve this problem. Various proportions of unbleached virgin eucalyptus and pine fibres were added to a recycled furnish used to manufacture liner paper for corrugated board. Laboratory sheets of each fibre blend were characterised by tensile, bursting and compressive strength. The change in the strength properties and moisture content of the sheets during refrigerated storage at 6°C and high relative humidity (90% RH) was also studied. The results showed that paper strength improved with the proportion of virgin fibres added. Pine fibres yielded higher increments than eucalyptus fibres in tensile and burst indices, whereas both fibres improved compression strength at a similar rate. After 4 h of exposure at refrigerated storage, the paper strength properties decreased considerably, in particular compression strength, which showed a loss of about 70% compared to the reference value. The percentage of strength lost compared to the value in standard conditions was influenced only by exposure time at low temperature and high RH. However, an increase in the amount of pine fibres added enhanced the remaining tensile and burst indices.

Enzymatic hydrolysis of pre-treated wheat straw has been studied. Several additives have been checked as potential improvers of glucose yield in the enzymatic hydrolysis, trying to avoid the cellulases inhibition by the lignin as a cause of the decrease of the saccharification rate of lignocellulosic biomass. Non-ionic surfactants, such as Tween 80 (poly(oxyethylene)20-sorbitan-monooleate) and polyethylene glycol-6000, and proteins, as bovine serum albumin, casein and skimmed milk powder, have been used to improve the sugars yield in the enzymatic hydrolysis. Two pre-treated wheat straw materials, one with high delignification and another with low delignification, have been tested. Three concentrations of each additive have been considered. The results obtained point out that the lignin content of the pre-treated lignocellulosic biomass has a decisive influence in reaching a high yield in the enzymatic saccharification. The additives checked have a moderate effect on the cellulose hydrolysis rate. The more favorable option combines high delignification with the use of a cheap protein such as casein, reaching a glucose yield of 88.6% when the best conditions are employed.

The technical viability was investigated for the conversion of Pinus pinaster stumps to value-added products via a chain of pretreatments and simultaneous saccharification and fermentation (SSF) steps to obtain bioethanol. Sequential steam explosion (SE), organosolv (OS) pretreatment and soda-anthraquinone pulping (Na/AQ) were performed resulting in an unbleached pulp (UBP), which was successfully converted via SSF to bioethanol with concentrations up to 79 g l-1, which corresponds to a conversion yield of 97% and productivity of 1.09 g l-1 h-1 at 15% total solids. Accordingly, delignification steps by oxygen bleaching are not necessary for bioethanol production. Different industrial softwood (SW) pulps were also tested as reference materials. Total lignin contents up to 4.5% in SW-based pulps had no adverse effects on SSF efficiency.

Enzymatic hydrolysis of three pre-treated lignocellulosic biomasses -LCB- (wheat straw-WS-, corn stover-CSV- and cardoon stems -CS-) is studied. These biomasses were pre-treated by two methods: diluted sulfuric acid and acid ethanol-water extraction at six severity levels (H values). Pretreated solid fractions were hydrolyzed with commercial enzyme cocktails at standard conditions. A first-order kinetic fractal model was fitted to the experimental results. This model accurately describes the hydrolysis of all biomasses at all pre-treatment conditions studied. The results show that the formal first-order kinetic constant k depends on the biomass nature. The hydrolysis rate increases as the pre-treatment severity does, while the fractal exponent value h decreases. With these pre-treatments, and in terms of k and h, WS is highly reactive and, at medium H with EW pretreatment, highly accessible; CSV has a low reactivity and high accessibility and CS has the lowest reactivity and an increasing accessibility as severity rises.

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.

Ethanol-water (EW) process, an efficient and low energy consumption method for lignocellulose fractionation, has been applied to the valorization of Cynara cardunculus (cardoon) as an integrated biorefinery raw material. Cardoon is a perennial plant fully adapted to low fertility soils and could be a solution to improve the biomass supply in rural areas with marginal lands. The purpose of this study is to optimize the fractionation of cardoon biomass, maximizing glucose yield in the subsequent enzymatic saccharification. Operational conditions have been optimized using Taguchi statistical approach, being the responses: recovery of glucans, hydrolysis yield of xylans, delignification yield and enzymatic hydrolysis rate. The variables studied have been: time, temperature, liquid/solid (L/S) ratio and ethanol concentration; each variable was studied at three levels. The best treatment conditions are achieved at the maximum tested values for time, temperature and L/S ratio (120 min, 190 °C and 30 L/kg, respectively), and the intermediate level for the ethanol concentration (33%). Nevertheless, temperature is the most influential variable and, with a moderate energy input (60 min, 190 °C, 20 L/kg and 25% of ethanol), cardoon retains most of the glucans (> 97%), while significant amounts of xylans (> 68%) and lignin (> 58%) are removed, resulting in a a high glucose yield (c.a. 72%) in the subsequent enzymatic saccharification process. Therefore, EW treatment leads to similar glucose yields if compared to other pre-treatments, but at a fraction of the energy input.

Ethanol-water (EW) and diluted sulfuric acid (DSA) pre-treatment have been studied for lignocellulosic biomass (corn stover, Cynara cardunculus L. stems and wheat straw). Both pre-treatments have been compared taken into account: solids recovery, glucans recovery, xylans removed, delignification and glucose yield. In all cases, the amount of energy involved has been taken as a criterion for sustainability. In general terms, EW is more efficient to remove lignin and DSA more appropriate to hydrolysate xylans. The combined effect of delignification and xylans removal is responsible for the improvement in the enzymatic cellulose hydrolysis. Under conditions of moderate-low energy inputs, EW pre-treatment yields better results than DSA with glucose yields in the range of 50–60% for EW pre-treated corn stover and cardoon stems; while wheat straw pulps reach up to 80%. So, multiple raw materials biorefinery needs a previous study to fit the type and conditions of the pre-treatment to each feedstock.

The ability of the bacteria Gluconacetobacter sucrofermentans to produce high-quality cellulose is well known. This bacterial cellulose has unique properties, as the result of an ultrathin crosslinked structure. It is almost chemically pure (until 98% cellulose), has a high crystallinity, mechanical strength, elasticity and durability. It is compatible with plant cellulose and could be grown on a vegetal fibrous network what makes bacterial cellulose an excellent candidate to reinforce damaged papers. The objective of this work is to promote the production of bacterial cellulose on the surface of a variety of papers by the direct application of a culture of G. sucrofermentans and to test if this procedure could be an economic and feasible possibility in reinforcing papers or cellulosic surfaces. After 7 days of cultivation, G. sucrofermentans deposits a thin layer (ca. 10 µm) of bacterial cellulose on the papers surfaces. Microscopic observations have shown a heterogeneous covering of the surfaces, while the modified papers maintain their thickness and their basic weight. The treatment has not increased the papers mechanical properties, but maintains them after artificial aging. The changes in optical properties of the reinforced papers, such as opacity and colorimetric coordinates, are minor even after further aging. Air permeance is the paper characteristic that experiences more variations because the layers of bacterial cellulose inhibit the airflow through the papers. The changes in the static and dynamic contact angles suggest that the bacterial cellulose structure is more compact and make the surface more hydrophobic than the original paper surface. © 2017, Springer Science+Business Media New York.

One of the most common methods used to reinforce damaged paper is to apply a lining, using Japanese paper (JP). The reinforcing material must consolidate the paper without modifying its visual appearance. The unique properties of bacterial cellulose (BC) suggest that it could be efficiently used to reinforce degraded paper documents. The changes in the visual appearances of the printed commercial papers lined with BC and JP were examined in this study. Four commercial papers, coated and uncoated, were printed with cyan, magenta, yellow, and black offset inks. The printed samples were lined with BC and JP sheets. Print density, gloss, and CIELab coordinates were tested in the lined and unlined samples before and after aging. Lining with JP notably affected the print density and CIELab coordinates. The lining with BC resulted in lower decrements in color intensity. The gloss values of samples lined with BC differed widely amongst the papers, whereas in papers reinforced with JP these values never exceeded 6%. Subjecting the samples to an aging process did not markedly modify the results except for the BC-lined samples, in which color differences increased.

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 Câ and CSEâ 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 Câ áµ£g and CSEâ â áµ£g. 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.

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.

[EN] As the fungal laccase production depends on some com-ponents which induce it, we have examined the indepen-dent effects of ethanol, wheat straw and copper sulphate and their combinations on the volumetric laccase activity of Pycnoporus sanguineus. Wheat straw and copper sulphate gave the best results showing a synergic effect after 13 days of incubation (lac-case activity was 3 and 4.5 times greater than the activ-ity generated when they were used alone). Ethanol on the contrary, was found to have a negative effect on laccase production.The laccase produced by the fungus Pycnoporus sanguin-eus maintains a good stability in a wide range of tempera-tures; a stability which also depends on the pH. By choos-ing the adequate pH, the level and stability of the laccase activity are satisfactory in a range of temperatures from 25 to 70ºC, which would allow the diversification of laccase use in industrial applications., [ES] Como la producción de lacasa fúngica depende de al-gunos componentes que la inducen, hemos estudiado el efecto del etanol, la paja de trigo y el sulfato de cobre de forma independiente y combinada sobre la actividad volu-métrica de la lacasa de Pycnoporus sanguineus. La paja de trigo y el sulfato de cobre han dado los mejores resultados, mostrando un efecto sinérgico en el décimo tercer día de incubación (la actividad lacasa fue 3 y 4,5 veces mayor que la actividad obtenida con cada uno de ellos por separado). Por el contrario, el etanol afectó nega-tivamente a la producción de lacasa. La lacasa producida por Pycnoporus sanguineus mantie-ne su estabilidad en un amplio intervalo de temperatura; estabilidad que depende también del pH. Eligiendo un pH adecuado, el nivel y la estabilidad de la actividad lacasa se mantienen satisfactoriamente a temperaturas entre 25 y 70ºC, lo que diversificaría el uso industrial de esta lacasa, [CAT] Donat que la producció de lacasa fúngica depèn d’alguns components que la indueixen, s’estudia l’efecte de l’eta-nol, la palla de blat i el sulfat de coure de forma indepen-dent i combinada sobre l’activitat volumètrica de la lacasa de Pycnoporus sanguineus. La palla de blat i el sulfat de coure donen els millors resul-tats, mostrant un efecte sinèrgic en el tretzè dia d’incuba-ció (l’activitat lacasa és 3 i 4,5 cops superior que l’activitat obtinguda amb cadascun d’ells per separat). Per contra, l’etanol afecta negativament a la producció de lacasa. La lacasa produïda per Pycnoporus sanguineus manté la seva estabilitat en un ampli interval de temperatura; esta-bilitat que depèn també del pH. Elegint un pH adequat, el nivell i l’estabilitat de l’activitat lacasa es mantenen satis-factòriament a temperatures entre 25 i 70ºC, el que diver-sificaria l’ús industrial d’aquesta lacasa.

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 (<150 rpm), 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 300 rpm 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. © 2016 Elsevier Ltd.

Enzymatic hydrolysis of corn stover was studied at agitation speeds from 50 to 500 rpm in a stirred tank bioreactor, at high solid concentrations (20% w/w dry solid/suspension), 50 °C and 15.5 mgprotein·gglucane −1. Two empirical kinetic models have been fitted to empirical data, namely a potential model and a fractal one. For the former case, the global order dramatically decreases from 13 to 2 as agitation speed increases, suggesting an increment in the access of enzymes to cellulose in terms of chemisorption followed by hydrolysis. For its part, the fractal kinetic model fits better to data, showing its kinetic constant a constant augmentation with increasing agitation speed up to a constant value at 250 rpm and above, when mass transfer limitations are overcome. In contrast, the fractal exponent decreases with rising agitation speed till circa 0.19, suggesting higher accessibility of enzymes to the substrate. © 2016 Elsevier Ltd

Preservation of documentary heritage is one of the biggest challenges facing paper conservators today. The singular properties of bacterial cellulose (BC) lead us to propose to reinforce paper with BC sheets. In the first part of this study, the reinforcing capability of BC was tested on model papers of well-known fiber composition. The aim of the present study was to verify the suitability of rebuilding degraded old papers with BC. The degraded papers were characterized before and after the reinforcement. In addition, lined samples were characterized before and after an aging process in order to study the stability in time. The same methodology was used with Japanese paper (JP), a material commonly used by paper conservators, in order to compare both materials as reinforcement. Mechanical properties of paper lined with BC are as good as those obtained with JP. Papers lined with BC have more marked modifications on their optical properties than those restored with JP. Nevertheless, letters in books lined with BC are more legible. Moreover, only the papers restored with BC show high changes in porosity. The aging process leads to a slight decrement in burst index. Changes on tear index and optical properties with the aging process depend on the paper to be restored. This study suggests that BC improves deteriorated paper quality, without altering the information contained therein, and that this improvement is maintained over time. Hence, BC is a promising alternative material for the restoration of paper. © 2015, Springer Science+Business Media New York.

The disappearance of bibliographic heritage is one of the biggest problems facing libraries. One of the most common methods used to restore paper, lining, is to apply a reinforcing layer to the document. This study focuses on lining papers with bacterial cellulose (BC) sheets from Gluconacetobacter sucrofermentans. For this purpose, several model papers have been selected. They have been characterized before and after the lining with this BC and a specific Japanese paper (JP) to compare both materials. Taking into account the differences between bacterial and vegetal cellulose is expected that the results may be similar to other BC and JP. The samples have been characterized before and after an aging process. There are no significant differences in some of the characteristics studied. Nevertheless, BC-lined papers present higher gloss values and b* coordinate. The wettability decreases with both BC and JP. However, in papers lined with BC, the wettability decreases more markedly and independently of the model paper used. This is related to the sealing of the surface structure by BC, which also leads to a reduction of air permeability. When the lined papers go through an aging process, there are no significant changes in any characteristic, except in b* and L* color coordinates. Additionally, the wettability rate decreases in all cases. This study indicates that papers lined with BC are stable over time. Finally, the use of BC as reinforcing material may offer advantages for specific conservation treatments, being more suitable for certain types of paper than JP. © 2015, Springer Science+Business Media New York.

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. © 2014 Elsevier Ltd.

Growing interest in alternative and renewable energy sources has brought increasing attention to the integration of a pulp mill into a forest biorefinery, where other products could be produced in addition to pulp. To achieve this goal, hemicelluloses were extracted, either by steam explosion or by steam treatment, from Eucalyptus globulus wood prior to pulping. The effects of both pre-treatments in the subsequent kraft pulping and paper strength were evaluated. Results showed a similar degree of hemicelluloses extraction with both options (32-67% of pentosans), which increased with the severity of the conditions applied. Although both pre-treatments increased delignification during pulping, steam explosion was significantly better 12.9 kappa number vs 22.6 for similar steam unexploded pulps and 40.7 for control pulp. Finally, similar reductions in paper strength were found regardless of the type of treatment and conditions assayed, which is attributed to the increase of curled and kinked fibers. © 2013 Elsevier Ltd.

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. © 2014 Elsevier Ltd.

Bacterial cellulose (BC) synthesized by Gluconacetobacter sucrofermentans has a high degree of crystallinity, durability, great resistance, and biocompatibility. This study evaluates the effect that carbon and nitrogen sources, present in HS (Hestrin-Schramm) culture medium, have on BC from G. sucrofermentans CECT 7291 used to restore damaged documents. The initial pH of the medium and the temperature were set for all assays, which were conducted in static conditions. The cellulose layers were obtained at four time points. The growth media were characterized at each time point (pH and carbon source consumption). Cellulose layers were washed, pressed, dried, and characterized by determining their pH, dry weight, and optical and mechanical properties. The best combination of carbon and nitrogen sources proved to be fructose plus yeast extract-corn steep liquor, with or without ethanol, which provided a good balance between BC production and carbon source consumption, and generated a resistant and homogeneous cellulose layer.

The production of laccase from Trametes sp. I-62 was optimized, and then it was applied for the first time in biobleaching in order to contribute to solve some problems associated with pulp bleaching. When wheat straw and copper sulfate were used in combination as inductors, the maximum laccase activity was obtained. The resulting enzymatic fluid was applied at optimum pH and temperature jointly with acetosyringone in a pretreatment stage (L) aimed to enhance the subsequent bleaching consisting of an alkaline extraction (E) and a hydrogen peroxide stage (P). Results showed that, even when a significantly lower amount of hydrogen peroxide was consumed in the LEP sequence (41.9% vs 89.9% for EP), higher delignification (40.6% vs 33.4%) and brightness (63.6 vs 56.3% ISO) were achieved. After accelerated aging, the optical properties of the biobleached pulp were found to be less stable but still remained higher than those of control pulps. © 2013 American Chemical Society.

Some pretreatments that swell and/or open the structure of wood fibers could increase the effectiveness of a biobleaching process, allowing for an industrial application. To this end, a chemical pretreatment (urea, U), a physical pretreatment (refining, R), and their combinations (RU and UR) were optimized to evaluate and compare their enhancement of the LE biobleaching sequence (laccase-mediator treatment plus alkali extraction). The urea pretreatment before biobleaching (ULE) provided the highest delignification (37.5%) and the highest increase in brightness (6.1 points % ISO). As expected, adding a refining process before or after the urea pretreatment increased paper strength. However, when the refining was applied after the urea pretreatment (URLE), the delignification was higher than that obtained after RULE. Thus, URLE provided a similar Kappa number and an increase of 97%, 149%, and 98% in the tensile, tear, and burst indexes, respectively, compared with ULE treatment, but it had a reduction of 2.8 points (% ISO) in brightness, caused by the action of refining. Therefore, depending on the final use of the paper (which can require high optical properties or high strength), either ULE or URLE would be the optimal sequence.

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 aim of this work is to study the reinforcement capacity of pulps obtained from Hesperaloe funifera using a simple and low energy consumption process (chemi refiner mechanical pulping) once they are added in different percentages to recycled pulps from newspaper and from old corrugated containers (OCC). Pinus radiata kraft pulp was used as a referent reinforcement material. H. funifera acted as a reinforcement material in newspaper and OCC recycled pulps, improving their optical and mechanical properties. While a 25% of H. funifera was the optimal amount added to reinforce the OCC pulp, only a 10% was needed for newspaper pulp. However, the OCC optimal mixture was better reinforced as it showed higher increase in all properties than the optimal newspaper mixture, apart from tensile index. Finally, all mixtures with P. radiata kraft pulp produce handsheet with lower properties, apart from tear index, suggesting than H. funifera is a better reinforcement material.

A non-wood raw material with high potential for pulp and paper applications (Hesperaloe funifera) was subjected to a steam explosion pre-treatment, and the subsequent effect of this pretreatment on biopulping and biobleaching was studied. An increase in the delignification rate, bigger than that reported for autohydrolysis and acid hydrolysis pre-treatments, and a reduction in chemical consumption were found during kraft pulping of the exploded samples. However, biopulping with the laccase-mediator system (LMS) did not lead to a reduction in the kappa number in either non-exploded or exploded unbleached pulps. On the other hand, the steam explosion pretreatment boosted the advantages of the LMS pre-treatment (decrease in kappa number and increase in brightness) favored biobleaching, with a 53.1% delignification rate and a final brightness of 67% ISO. Finally, the steam explosion pre-treatment also improved the color properties of the bleached pulp and reduced the hydrogen peroxide consumption by 24.6%. © 2012 Elsevier Ltd.

The aim of this work was to evaluate the response to biobleaching of steam exploded kraft pulps and to compare the results with the controls. For this end, a laccase-mediator treatment using commercial laccase (Novozyme 51003) and a natural mediator (acetosyringone) were assayed, followed by alkaline extraction and hydrogen peroxide stages. Our approach resulted in exploded biobleached pulps with lower kappa number and improved optical properties compared to controls, even after subjecting pulps to accelerated ageing. Additionally, use of hydrogen peroxide was reduced. The LMS (laccase-mediator system) had a smaller impact on the properties of the bleached pulps and on hydrogen peroxide consumption than the steam explosion process did. © 2010 Elsevier Ltd.

The effect of a pretreatment consisting of steam explosion (SE) followed by a laccase mediator system (LMS) stage on Eucalyptus globulus kraft pulping has been evaluated and compared with fungal pretreatments. Pretreatment with SE and LMS was more efficient than pretreatments using Pycnoporus sanguineus and Trametes sp. I-62. Steam explosion not only improved the enzyme penetration into the wood chips and shortened the pulping process by 60%, but also extracted around 50% of the hemicelluloses which could be converted into value-added products. The optimal conditions for the LMS treatment were 3h, 3UA/g and 40°C. Compared to SE, the SE/LMS treatment yielded an increase in delignification of 13.9% without affecting pulp properties, provided a similar screened kraft yield, and reduced consumption of chemical reagents Na2S and NaOH by 11.5% and 6.3%, respectively. Therefore, SE/LMS is a promising pretreatment for converting the pulp mill into a forest bio-refinery. © 2011 Elsevier Ltd.

Steam explosion has been proposed for a wide range of lignocellulosic applications, including fractionation of biomass, pre-treatment of biomass for ethanol production, or as an alternative to conventional mechanical pulping. Nevertheless, a steam explosion process could also be used as pretreatment before chemical pulping, expecting a reduction in cooking time due to the open structure of the exploded chips. Thus, to evaluate the effect of steam explosion as a pretreatment in the kraft pulping of Eucalyptus globulus, steam exploded chips and control chips were subjected to kraft cookings. Steam exploded chips provided pulps with reductions of kappa number by up to 70% with no significant change in viscosity. Therefore, the cooking time could be shortened by 60%, increasing the productivity and obtaining pulps with similar delignification degree to those of the control pulp. Furthermore, not only the production rate could be increased, but also most of the hemicelluloses could be recovered before pulping and converted to a value-added product. Finally, although exploded pulp had inferior mechanical strength, the optical properties, which are more important in eucalyptus pulps, were found to be better.

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.