The use of carbohydrate binding modules (CBMs) to monitor changes in fragmentation and cellulose fiber surface morphology during cellulase- and Swollenin-induced deconstruction of lignocellulosic substrates.

Although the actions of many of the hydrolytic enzymes involved in cellulose hydrolysis are relatively well understood, the contributions that amorphogenesis-inducing proteins might contribute to cellulose deconstruction are still relatively undefined. Earlier work has shown that disruptive proteins, such as the non-hydrolytic non-oxidative protein Swollenin, can open up and disaggregate the less-ordered regions of lignocellulosic substrates. Within the cellulosic fraction, relatively disordered, amorphous regions known as dislocations are known to occur along the length of the fibers. It was postulated that Swollenin might act synergistically with hydrolytic enzymes to initiate biomass deconstruction within these dislocation regions. Carbohydrate binding modules (CBMs) that preferentially bind to cellulosic substructures were fluorescently labeled. They were imaged, using confocal microscopy, to assess the distribution of crystalline and amorphous cellulose at the fiber surface, as well as to track changes in surface morphology over the course of enzymatic hydrolysis and fiber fragmentation. Swollenin was shown to promote targeted disruption of the cellulosic structure at fiber dislocations.

Exploring xylan removal via enzymatic post-treatment to tailor the properties of cellulose nanofibrils for packaging film applications.

Hemicellulose plays a key role in both the production of cellulose nanofibrils (CNF) and their properties as suspensions and films. While the use of enzymatic and chemical pre-treatments for tailoring hemicellulose levels is well-established, post-treatment methods using enzymes remain relatively underexplored and hold significant promise for modifying CNF film properties. This study aimed to investigate the effects of enzymatic xylan removal on the properties of CNF film for packaging applications. The enzymatic post-treatment was carried out using an enzymatic cocktail enriched with endoxylanase (EX). The EX post-treated-CNFs were characterized by LALLS, XRD, and FEG-SEM, while their films were characterized in terms of physical, morphological, optical, thermal, mechanical, and barrier properties. Employing varying levels of EX facilitated the hydrolysis of 8 to 35 % of xylan, yielding CNFs with different xylan contents. Xylan was found to be vital for the stability of CNF suspensions, as its removal led to the agglomeration of nanofibrils. Nanostructures with preserved crystalline structures and different morphologies, including nanofibers, nanorods, and their hybrids were observed. The EX post-treatment contributed to a smoother film surface, improved thermostability, and better moisture barrier properties. However, as the xylan content decreased, the films became lighter (lower grammage), less strong, and more brittle. Thus, the enzymatic removal of xylan enabled the customization of CNF films' performance without affecting the inherent crystalline structure, resulting in materials with diverse functionalities that could be explored for use in packaging films.

From production to performance: Tailoring moisture and oxygen barrier of cellulose nanomaterials for sustainable applications - A review.

Barrier materials are crucial in preserving product quality, safety and longevity across numerous applications, thereby contributing to sustainability, reducing waste and advancing technology. Among these materials, cellulose nanomaterials (CNs) have emerged as promising alternatives for traditional petroleum-based polymers. However, the wide range of sources and the different methods used to isolate and process CN-based materials can result in significant variations in moisture and oxygen barrier performance. In this review, we provide an in-depth discussion on the latest advancements in CN-based green barrier materials. We begin by offering a critical assessment of the barrier performance of CNs, both in their isolated form and when combined as hybrid materials. This includes their applications as standalone films, fillers and coatings in nanocomposites. This review also covers the influence of the isolation process and the stages of film formation on barrier efficacy. We further discuss the implications of the recycling process on barrier properties of CN-based materials, drawing a connection between barrier characteristics and the product's end-of-life. We conclude by highlighting the significant developments over the past five years, the present challenges, and the prospective future of CN-based materials in barrier applications.

Evaluating the reinforcing potential of enzymatic cellulose nanocrystals in polypropylene nanocomposite.

Cellulose nanocrystals (CNCs) produced through enzymatic hydrolysis exhibit physicochemical properties that make them attractive as eco-friendly reinforcing agents in polymer composites. However, the extent of their efficacy within a polymeric matrix is yet to be fully established. This study investigated the reinforcing capabilities of enzymatic CNC (approximately 3 nm in diameter) isolated from bleached eucalyptus Kraft pulp (BEKP), focusing on its application in polypropylene (PP) nanocomposites produced by injection molding. The study compared the performance of this enzymatic CNC (1-5 % wt) with PP composites reinforced with micro-sized cellulose fibers (BEKP at 10-30 % wt, approximately 13 µm) and additionally with commercial CNC produced by sulfuric acid hydrolysis. Despite enzymatic CNC experiencing agglomeration during spray-drying, leading to an average diameter increase to 3 µm, it still significantly increased the crystallization and glass transition temperature of the PP matrix. However, this agglomeration likely hindered the improvement of the mechanical properties within the nanocomposites. The results also showed that enzymatic CNC provided higher thermal stability at lower reinforcement levels compared to BEKP, but this came with a reduction in stiffness, posing a significant consideration in composite design. The addition of a coupling agent greatly enhanced the dispersion of reinforcements and the interfacial adhesion within the matrix, contributing to the enhanced performance of the composite properties. Additionally, enzymatic CNC demonstrated potential for superior reinforcement efficacy compared to commercially available CNC produced by sulfuric acid hydrolysis. In conclusion, enzymatic CNC exhibited a promising role as nano-reinforcement for thermoplastic polymer nanocomposites, exhibiting higher thermal properties at lower reinforcing loads than traditional micro-sized fiber reinforcements. The absence of sulfur, coupled with its higher thermal stability and sustainable potential, positions enzymatic CNC as a particularly favorable choice for applications involving direct contact with food, cosmetics, pharmaceuticals, and biomedical materials.

Bacterial cellulose nanocrystals obtained through enzymatic and acidic routes: A comparative study of their main properties and in vitro biological responses.

Cellulose nanocrystals (CNCs) are crystalline domains isolated from cellulosic fibers. They have been utilized in a wide range of applications, such as reinforcing fillers, antibacterial agents and manufacturing of biosensors. Whitin this context, the aim of this work was to obtain and analyze CNCs extracted from bacterial nanocellulose (BNC) using two distinct methods combined with milling pre-treatment: an acidic hydrolysis using 64 % sulfuric acid and an enzymatic hydrolysis using a commercial cellulase enzyme mixture. The CNCs obtained from the enzymatic route (e-CNCs) were observed to be spherical nanoparticles with diameter of 56 ± 11 nm. In contrast, the CNCs from the acid hydrolysis (a-CNCs) appeared as needle-shaped nanoparticles with a high aspect ratio with lengths/widths of 158 ± 64 nm/11 ± 2 nm. The surface zeta potential (ZP) of the a-CNCs was -30,8 mV, whereas the e-CNCs has a potential of +2.70 ± 3.32 mV, indicating that a-CNCs consisted of negatively charged particles with higher stability in solution. Although the acidic route resulted in nanocrystals with a slightly higher crystallinity index compared to the enzymatic route, e-CNCs was found to be more thermally stable than BNC and a-CNCs. Here, we also confirmed the safety of a-CNCs and e-CNCs using L929 cell line. Lastly, this article describes two different CNCs synthesis approaches that leads to the formation of nanoparticles with different dimensions, morphology and unique physicochemical properties. To the best of our knowledge, this is the first study to yield spherical nanoparticles as a result of BNC enzymatic treatment.

Endoglucanase pretreatment aids in isolating tailored-cellulose nanofibrils combining energy saving and high-performance packaging.

Cellulose nanofibrils (CNFs) have emerged as a potential alternative to synthetic polymers in packaging applications owing to their oxygen and grease barrier performance, as well as their strong mechanical properties. However, the performance of CNF films relies on the inherent characteristics of fibers, which undergo changes during the CNF isolation process. Understanding these variations in characteristics during CNF isolation is crucial for tailoring CNF film properties to achieve optimum performance in packaging applications. In this study, CNFs were isolated by endoglucanase-assisted mechanical ultra-refining. The alterations in the intrinsic characteristics of CNFs and their impact on CNF films were systematically investigated by considering the degree of defibrillation, enzyme loading, and reaction time through a design of experiments. Enzyme loading had a significant influence on the crystallinity index, crystallite size, surface area, and viscosity. Meanwhile, the degree of defibrillation greatly affected the aspect ratio, degree of polymerization, and particle size. CNF films prepared from CNFs isolated under two optimized scenarios (casting and coating applications) exhibited remarkable properties, including high thermal stability (approximately 300 °C), high tensile strength (104 - 113 MPa), excellent oil resistance (kit n°12), and low oxygen transmission rate (1.00 - 3.17 cc·m-2.day-1). Therefore, endoglucanase pretreatment can aid in obtaining CNFs with lower energy consumption, resulting in films that possess higher transmittance, superior barrier performance, and reduced surface wettability compared to control samples without enzymatic pretreatment and other unmodified CNF films reported in the literature, all while maintaining mechanical and thermal performance without significant loss.

High-yield production of rod-like and spherical nanocellulose by controlled enzymatic hydrolysis of mechanically pretreated cellulose.

In this study, a simple and scalable mechanical pretreatment was evaluated as means of enhancing the accessibility of cellulose fibers, with the objective of improving the efficiency of enzymatic reactions for the production of cellulose nanoparticles (CNs). In addition, the effects of enzyme type (endoglucanase - EG, endoxylanase - EX, and a cellulase preparation - CB), composition ratio (0-200UEG:0-200UEX or EG, EX, and CB alone), and loading (0 U-200 U) were investigated in relation to CN yield, morphology, and properties. The combination of mechanical pretreatment and specific enzymatic hydrolysis conditions substantially improved CN production yield, reaching up to 83 %. The production of rod-like or spherical nanoparticles and their chemical composition were highly influenced by the enzyme type, composition ratio, and loading. However, these enzymatic conditions had minimal impact on the crystallinity index (approximately 80 %) and thermal stability (Tmax within 330-355 °C). Overall, these findings demonstrate that mechanical pretreatment followed by enzymatic hydrolysis under specific conditions is a suitable method to produce nanocellulose with high yield and adjustable properties such as purity, rod-like or spherical forms, high thermal stability, and high crystallinity. Therefore, this production approach shows promise in producing tailored CNs with the potential for superior performance in various advanced applications, including, but not limited to, wound dressings, drug delivery, thermoplastic composites, 3D (bio)printing, and smart packaging.

Hydrophobic enzymatic cellulose nanocrystals via a novel, one-pot green method.

Cellulose nanocrystals (CNCs) are a rapidly growing bionanomaterial with remarkable properties that have been harnessed in various applications, including mechanical reinforcement, biomedical materials, and coatings. However, for non-water-based applications, hydrophobization of CNCs while preserving their integrity is crucial. In this study, we propose a new eco-friendly, one-pot surface esterification method for hydrophobizing enzymatic CNCs in aqueous suspension without solvent exchange. By establishing an appropriate set of reaction conditions, it was possible to create a miscibility gradient that enabled a low-cost, and renewable fatty acid to be utilized as an acyl donor and solvent, allowing direct hydrophobic modification of the as-produced aqueous suspension of enzymatic CNC. FT-IR and AFM-IR analyses confirmed the formation of ester groups, while 13C NMR confirmed the emergence of carboxyl groups. XPS revealed a high degree of surface substitution (0.39) in the modified CNC, while a substantial increase in contact angle (from 40 to approximately 90°) quantitatively confirmed the high efficiency of the enzymatic CNC's hydrophobic modification. Additionally, important properties such as morphology remained practically unchanged, except for a slight increase in thermal stability and crystallinity of the CNCs. Therefore, hydrophobic enzymatic CNCs were successfully produced via a simple, scalable, and environmentally friendly approach without compromising their properties. These hydrophobic CNCs have the potential to enhance nanocomposite compatibility, improve packaging performance for electronics and foods, optimize adhesion in coatings, and offer advancements in cosmetics and drug delivery. However, comprehensive studies are needed to confirm their applicability across these sectors.

The emergence of hybrid cellulose nanomaterials as promising biomaterials.

Cellulose nanomaterials (CNs) are promising green materials due to their unique properties as well as their environmental benefits. Among these materials, cellulose nanofibrils (CNFs) and nanocrystals (CNCs) are the most extensively researched types of CNs. While they share some fundamental properties like low density, biodegradability, biocompatibility, and low toxicity, they also possess unique differentiating characteristics such as morphology, rheology, aspect ratio, crystallinity, mechanical and optical properties. Therefore, numerous comparative studies have been conducted, and recently, various studies have reported the synergetic advantages resulting from combining CNF and CNC. In this review, we initiate by addressing the terminology used to describe combinations of these and other types of CNs, proposing "hybrid cellulose nanomaterials" (HCNs) as the standardized classifictation for these materials. Subsequently, we briefly cover aspects of properties-driven applications and the performance of CNs, from both an individual and comparative perspective. Next, we comprehensively examine the potential of HCN-based materials, highlighting their performance for various applications. In conclusion, HCNs have demonstraded remarkable success in diverse areas, such as food packaging, electronic devices, 3D printing, biomedical and other fields, resulting in materials with superior performance when compared to neat CNF or CNC. Therefore, HCNs exhibit great potential for the development of environmentally friendly materials with enhanced properties.

Endoglucanase effects on energy consumption in the mechanical fibrillation of cellulose fibers into nanocelluloses.

Enzymatic processing is considered a promising approach for advancing environmentally friendly industrial processes, such as the use of endoglucanase (EG) enzyme in the production of nanocellulose. However, there is ongoing debate regarding the specific properties that make EG pretreatment effective in isolating fibrillated cellulose. To address this issue, we investigated EGs from four glycosyl hydrolase (GH) families (5, 6, 7, and 12) and examined the roles of the three-dimensional structure and catalytic features, with a focus on the presence of a carbohydrate binding module (CBM). Using eucalyptus Kraft wood fibers, we produced cellulose nanofibrils (CNFs) through mild enzymatic pretreatment, followed by disc ultra-refining. Comparing the results with the control (without pretreatment), we observed that GH5 and GH12 enzymes (without CBM) reduced fibrillation energy by approximately 15 %. The most significant energy reduction, 25 and 32 %, was achieved with GH5 and GH6 linked to CBM, respectively. Notably, these CBM-linked EGs improved the rheological properties of CNF suspensions without releasing soluble products. In contrast, GH7-CBM exhibited significant hydrolytic activity, resulting in the release of soluble products, but did not contribute to a reduction in fibrillation energy. This discrepancy can be attributed to the large molecular weight and wide cleft of GH7-CBM, which led to the release of soluble sugars but had little impact on fibrillation. Our findings suggest that the improved fibrillation observed with EG pretreatment is primarily driven by efficient enzyme adsorption on the substrate and modification of the surface viscoelasticity (amorphogenesis), rather than hydrolytic activity or release of products.

Peculiarities of brown-rot fungi and biochemical Fenton reaction with regard to their potential as a model for bioprocessing biomass.

This work reviews the brown-rot fungal biochemical mechanism involved in the biodegradation of lignified plant cell walls. This mechanism has been acquired as an apparent alternative to the energetically expensive apparatus of lignocellulose breakdown employed by white-rot fungi. The mechanism relies, at least in the incipient stage of decay, on the oxidative cleavage of glycosidic bonds in cellulose and hemicellulose and the oxidative modification and arrangement of lignin upon attack by highly destructive oxygen reactive species such as the hydroxyl radical generated non-enzymatically via Fenton chemistry [Formula: see text]. Modifications in the lignocellulose macrocomponents associated with this non-enzymatic attack are believed to aid in the selective, near-complete removal of polysaccharides by an incomplete cellulase suite and without causing substantial lignin removal. Utilization of this process could provide the key to making the production of biofuel and renewable chemicals from lignocellulose biomass more cost-effective and energy efficient. This review highlights the unique features of the brown-rot fungal non-enzymatic, mediated Fenton reaction mechanism, the modifications to the major plant cell wall macrocomponents, and the implications and opportunities for biomass processing for biofuels and chemicals.

Xylanase increases the selectivity of the enzymatic hydrolysis with endoglucanase to produce cellulose nanocrystals with improved properties.

Enzyme-mediated isolation of cellulose nanocrystals (CNCs) is a promising environment friendly method with expected lower capital and operating expenditures compared to traditional processes. However, it is still poorly understood. In this study, an endoxylanase was applied as accessory enzyme to assess its potential to increase the selectivity of an endoglucanase during cellulose hydrolysis to isolate CNCs with improved properties. Only combinations of the enzymes with xylanase activity equal to or higher than the endoglucanase activity resulted in CNCs with improved properties (i.e., crystallinity, thermostability, uniformity, suspension stability and aspect ratio). The beneficial effects of the accessory enzyme are related to its hydrolytic (xylan and cellulose hydrolysis) and non-hydrolytic action (swelling of cellulose fibers and fiber porosity) and on the ratio of the enzymes, which in turn allows to tailor the properties of the CNCs. In conclusion, compared to the traditional sulfuric acid hydrolysis method, accessory enzymes help to isolate cellulose nanomaterials with improved and customized (sizes, aspect ratio and morphology) properties that may allow for new applications.

Paludibacter propionicigenes GH10 xylanase as a tool for enzymatic xylooligosaccharides production from heteroxylans.

Bioconversion of lignocellulosic biomass into value-added products relies on polysaccharides depolymerization by carbohydrate active enzymes. This work reports biochemical characterization of Paludibacter propionicigenes xylanase from GH10 (PpXyn10A) and its application for enzymatic xylooligosaccharides (XOS) production from commercial heteroxylans and liquor of hydrothermally pretreated corn cobs (PCC). PpXyn10A is tolerant to ethanol and NaCl, and releases xylobiose (X2) and xylotriose (X3) as the main hydrolytic products. The conversion rate of complex substrates into short XOS was approximately 30% for glucuronoxylan and 8.8% for rye arabinoxylan, after only 4 h; while for PCC, PpXyn10A greatly increased unbranched XOS yields. B. adolescentis fermentation with XOS from beechwood glucuronoxylan produced mainly acetic and lactic acids. Structural analysis shows that while the glycone region of PpXyn10A active site is well preserved, the aglycone region has aromatic interactions in the +2 subsite that may explain why PpXyn10A does not release xylose.

Lignocellulosic polysaccharides and lignin degradation by wood decay fungi: the relevance of nonenzymatic Fenton-based reactions.

The brown rot fungus Wolfiporia cocos and the selective white rot fungus Perenniporia medulla-panis produce peptides and phenolate-derivative compounds as low molecular weight Fe³+-reductants. Phenolates were the major compounds with Fe³+-reducing activity in both fungi and displayed Fe³+-reducing activity at pH 2.0 and 4.5 in the absence and presence of oxalic acid. The chemical structures of these compounds were identified. Together with Fe³+ and H2O2 (mediated Fenton reaction) they produced oxygen radicals that oxidized lignocellulosic polysaccharides and lignin extensively in vitro under conditions similar to those found in vivo. These results indicate that, in addition to the extensively studied Gloeophyllum trabeum--a model brown rot fungus--other brown rot fungi as well as selective white rot fungi, possess the means to promote Fenton chemistry to degrade cellulose and hemicellulose, and to modify lignin. Moreover, new information is provided, particularly regarding how lignin is attacked, and either repolymerized or solubilized depending on the type of fungal attack, and suggests a new pathway for selective white rot degradation of wood. The importance of Fenton reactions mediated by phenolates operating separately or synergistically with carbohydrate-degrading enzymes in brown rot fungi, and lignin-modifying enzymes in white rot fungi is discussed. This research improves our understanding of natural processes in carbon cycling in the environment, which may enable the exploration of novel methods for bioconversion of lignocellulose in the production of biofuels or polymers, in addition to the development of new and better ways to protect wood from degradation by microorganisms.

High yield biorefinery products from sugarcane bagasse: Prebiotic xylooligosaccharides, cellulosic ethanol, cellulose nanofibrils and lignin nanoparticles.

An integrated biorefining strategy was applied to fractionate Sugarcane bagasse (SCB) into its major constituents, enabling high-yield conversion of the fractionated materials into high-value coproducts alongside cellulosic ethanol. Pilot-scale steam explosion produced a hydrolysate rich in low molecular weight xylooligosaccharides that had a high in vitro efficacy as a prebiotic towards different bifidobacteria. Lignin recovered after alkaline treatment of the steam-exploded SCB was converted into uniform spherical lignin nanoparticles (11.3 nm in diameter) by a green mechanical method. The resulting cellulose was hydrolyzed at 17.5% (w/v) consistency and low enzyme loading (17.5 mg/g) to yield a pure glucose hydrolysate at a high concentration (100 g/L) and a cellulosic solid residue that was defibrillated by disc ultra-refining into homogeneous cellulose nanofibrils (20.5 nm in diameter). Statistical optimization of the cellulosic hydrolysate fermentation led to ethanol production of 67.1 g/L, with a conversion yield of 0.48 g/g and productivity of 1.40 g/L.h.

Effect of chemical treatment of pineapple crown fiber in the production, chemical composition, crystalline structure, thermal stability and thermal degradation kinetic properties of cellulosic materials.

Recently, the growing environmental concerns and economic demands have driven the need to develop effective solutions for the treatment of vegetal fibers to be used as renewable source for various industrial applications. The present study aimed to explore pineapple crown fibers (PCs) as an alternative source of cellulose. The three treatments (alcohol-insoluble residue (AIR), alkaline (AT), and organosolv) evaluated promoted chemical and morphological changes to the PCs. Fresh and treated PCs were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), thermogravimetric analysis (TG), and chemical composition. The XRD results showed that the Cellulose-I allomorph was not altered during extraction, and that the crystallinity index of the fibers treated with AT, first bleaching step, second bleaching step, and the second bleaching step followed by KOH treatment (2B_KOH) increased to 77.8; 83.2; 83.5 and 86% when compared with fresh PC (62.3%). Results from the thermal analysis revealed that thermal stability increased for the isolated cellulose, and the maximum degradation for (2B_KOH) is 350 °C. Chemical composition results showed a decrease in the content of hemicellulose, lignin and other soluble materials after alkaline treatment, suggesting high-quality 2B_KOH with 74.6% of cellulose. SEM revealed changes in the morphological structure on fibers. Alkaline treatment followed by H2O2 bleaching is an excellent alternative for the removal of non-cellulosic material and facilitates the isolation of cellulose. These results suggested that there is a potential to isolate cellulose from PC via the sequence of treatment of a methodology by chlorite-free.

Co-production of xylo-oligosaccharides, xylose and cellulose nanofibrils from sugarcane bagasse.

This work investigated the integration of a two-stage hydrothermal treatment for production of xylooligosaccharides (XOS), a high-value product, into the isolation process of cellulose nanofibrils (CNF) from sugarcane bagasse. Under optimized conditions, the first stage yielded a XOS-rich, high purity hydrolysate and in the second stage only a xylose-rich hydrolysate could be obtained at high purity. The resulting solid cellulosic fraction was delignified and bleached to obtain a cellulose-rich pulp, which was mechanically defibrillated by disc ultra-refining to CNF. Except for the viscosity, the sugarcane CNF showed properties (i.e., thermal stability, crystallinity and diameter size) comparable or superior to the CNF prepared from commercial bleached eucalyptus Kraft pulp. In conclusion, the integration of the two-stage hydrothermal treatment is an efficient and promising strategy to obtain hemicellulose-derived high-value co-products in the process of isolating CNF. In addition, lignin was also recovered as a co-product with yield comparable to other biomass fractionation approaches.

Biomimetic oxidative treatment of spruce wood studied by pyrolysis-molecular beam mass spectrometry coupled with multivariate analysis and 13C-labeled tetramethylammonium hydroxide thermochemolysis: implications for fungal degradation of wood.

In this work, pyrolysis-molecular beam mass spectrometry analysis coupled with principal components analysis and (13)C-labeled tetramethylammonium hydroxide thermochemolysis were used to study lignin oxidation, depolymerization, and demethylation of spruce wood treated by biomimetic oxidative systems. Neat Fenton and chelator-mediated Fenton reaction (CMFR) systems as well as cellulosic enzyme treatments were used to mimic the nonenzymatic process involved in wood brown-rot biodegradation. The results suggest that compared with enzymatic processes, Fenton-based treatment more readily opens the structure of the lignocellulosic matrix, freeing cellulose fibrils from the matrix. The results demonstrate that, under the current treatment conditions, Fenton and CMFR treatment cause limited demethoxylation of lignin in the insoluble wood residue. However, analysis of a water-extractable fraction revealed considerable soluble lignin residue structures that had undergone side chain oxidation as well as demethoxylation upon CMFR treatment. This research has implications for our understanding of nonenzymatic degradation of wood and the diffusion of CMFR agents in the wood cell wall during fungal degradation processes.

A review on commercial-scale high-value products that can be produced alongside cellulosic ethanol.

The demand for fossil derivate fuels and chemicals has increased, augmenting concerns on climate change, global economic stability, and sustainability on fossil resources. Therefore, the production of fuels and chemicals from alternative and renewable resources has attracted considerable and growing attention. Ethanol is a promising biofuel that can reduce the consumption of gasoline in the transportation sector and related greenhouse gas (GHG) emissions. Lignocellulosic biomass is a promising feedstock to produce bioethanol (cellulosic ethanol) because of its abundance and low cost. Since the conversion of lignocellulose to ethanol is complex and expensive, the cellulosic ethanol price cannot compete with those of the fossil derivate fuels. A promising strategy to lower the production cost of cellulosic ethanol is developing a biorefinery which produces ethanol and other high-value chemicals from lignocellulose. The selection of such chemicals is difficult because there are hundreds of products that can be produced from lignocellulose. Multiple reviews and reports have described a small group of lignocellulose derivate compounds that have the potential to be commercialized. Some of these products are in the bench scale and require extensive research and time before they can be industrially produced. This review examines chemicals and materials with a Technology Readiness Level (TRL) of at least 8, which have reached a commercial scale and could be shortly or immediately integrated into a cellulosic ethanol process.

Kinetic changes in cellulose properties during defibrillation into microfibrillated cellulose and cellulose nanofibrils by ultra-refining.

Defibrillation of cellulose fibers can lead to the isolation of microfibrillated cellulose (MFC) or cellulose nanofibrils (CNF) with intrinsic properties suitable for various applications. However, to what extent these properties are preserved, enhanced, gained or lowered during defibrillation and how they are related remains unclear. In this study, a kinetic study of the ultra-refining of bleached eucalyptus Kraft pulp (BEKP) in a disc ultra-refiner was performed and characterized in terms of physical-structural, morphological and thermal properties and their interactions and compromises. Defibrillation of BEKP to MFC substantially decreased the fiber diameter and increased viscosity, surface area and morphological heterogeneity. It also led to a remarkable increase in transparency and essentially did not alter the thermostability but significantly degraded the crystallinity. A higher degree of defibrillation to isolate CNF led to fibers with smaller diameter and increased diameter uniformity but required a substantial amount of energy to only marginally increase viscosity and transparency. Crystallinity and thermostability were not altered, comparing with CMF. In conclusion, most changes occurred during the defibrillation of BEKP to CMF. Further defibrillation to CNFs with smaller diameters and better uniformity did not significantly reflect on other important structural cellulose physical properties, despite the much higher energy consumption and degree of defibrillation.