Kinetics of Strong Acid Hydrolysis of a Bleached Kraft Pulp for Producing Cellulose Nanocrystals (CNCs)

Cellulose nanocrytals (CNCs) are predominantly produced using the traditional strong acid hydrolysis process. In most reported studies, the typical CNC yield is low (approximately 30%) despite process optimization. This study investigated the hydrolysis of a bleached kraft eucalyptus pulp using sulfuric acid between 50 and 64 wt % at temperatures of 35–80 °C over time periods of up to 240 min for the production of CNCs. The experimental design captured the feature of the coexistence of a variety of reaction products, such as CNC, cellulosic solid residue (CSR), glucose, and xylose, in the product stream for accurate kinetic modeling to improve the CNC production yield. The kinetic model describing the solubilization of cellulose fibers used three phenomenological reactions, namely, hydrolysis of xylan to form xylose, depolymerization of cellulose to CNCs, and hydrolysis of cellulose to form glucose, each of which can be described by pseudohomogenous first-order kinetics. The concept of “degrees of hydrolyzable xylan or cellulose” to reflect the inhomogeneity of xylan or cellulose in hydrolysis was incorporated into the kinetic modeling to improve model accuracy. The developed model showed excellent predictability for CNC production. Both the experimental data and the model clearly indicate that CNC production was limited by cellulose depolymerization at low acid concentrations of below 58 wt %, but controlled by CNC degradation when the acid concentration was higher than 58 wt %. This work for the first time provides the most plausible description of CNC production kinetics, which is significant for the commercial production of CNCs

Hydrogels Prepared from Cross-Linked Nanofibrillated Cellulose

Nanocomposite hydrogels were developed by cross-linking nanofibrillated cellulose with poly­(methyl vinyl ether-co-maleic acid) and polyethylene glycol. The cross-linked hydrogels showed enhanced water absorption and gel content with the addition of nanocellulose. In addition, the thermal stability, mechanical strength, and modulus increased with an increase in the amount of nanocellulose in hydrogels, and this can be attributed to efficient cross-linking between the nanocellulose and the matrix. The addition of softwood nanocellulose showed much higher strength and strain properties in the hydrogels than with the addition of hardwood nanocellulose. The enhanced physical properties confirm that in situ cross-linking of nanofibrillated cellulose with the matrix polymer forms hydrogels that are not just blends of starting materials but are distinctively unique and formed by cross-linking interactions between the filler and matrix

Biorefinery Lignosulfonates from Sulfite-Pretreated Softwoods as Dispersant for Graphite

Two biorefinery lignosulfonates (LSs), Ca-LS-DF and Na-LS-LP, were, respectively, isolated from pilot-scale sulfite-pretreated spent liquor of lodgepole pine and fermentation residue of Douglas-fir harvest forest residue. The molecular weights of Na-LS-LP and Ca-LS-DF were approximately 9 000 and 11 000 Da, respectively. The two LSs were applied as dispersant for graphite in aqueous suspensions. The dispersion stability was evaluated by a scanning electron microscope and Turbiscan Lab Expert. LS performance in modifying graphite was better than that of a commercial dispersant Reax-85A as indicated by the Turbiscan TSI values, zeta potential of suspension particles, and SEM imaging. The practical importance of this study lies in the fact that the pilot-scale sulfite pretreatments that produced the two LSs also produced excellent bioethanol yields at high titer without detoxification and washing, suggesting the LSs are a true value-added coproduct for high yield biofuel production

Contribution of Residual Proteins to the Thermomechanical Performance of Cellulosic Nanofibrils Isolated from Green Macroalgae

Cellulosic nanofibrils (CNFs) were isolated from one of the most widespread freshwater macroalgae, Aegagropila linnaei. The algae were first carboxylated with a recyclable dicarboxylic acid, which facilitated deconstruction into CNFs via microfluidization while preserving the protein component. For comparison, cellulosic fibrils were also isolated by chemical treatment of the algae with sodium chlorite. Compared with the energy demanded for deconstruction of wood fibers, algal biomass required substantially lower levels. Nevertheless, the resultant nanofibrils were more crystalline (crystallinity index > 90%) and had a higher degree of polymerization (DP > 2500). Taking advantage of these properties, algal CNFs were used to produce films or nanopapers (tensile strength of up to 120 MPa), the strength of which resulted from protein-enhanced interfibrillar adhesion. Besides being translucent and flexible, the nanopapers displayed unusually high thermal stability (up to 349 °C). Overall, we demonstrate a high-end utilization of a renewable bioresource that is available in large volumes, for example, in the form of algal blooms

Knockdown of Hsc70-5/mortalin induces loss of synaptic mitochondria in a Drosophila Parkinson's disease model

Mortalin is an essential component of the molecular machinery that imports nuclear-encoded proteins into mitochondria, assists in their folding, and protects against damage upon accumulation of dysfunctional, unfolded proteins in aging mitochondria. Mortalin dysfunction associated with Parkinson's disease (PD) increases the vulnerability of cultured cells to proteolytic stress and leads to changes in mitochondrial function and morphology. To date, Drosophila melanogaster has been successfully used to investigate pathogenesis following the loss of several other PD-associated genes. We generated the first loss-of-Hsc70-5/mortalin-function Drosophila model. The reduction of Mortalin expression recapitulates some of the defects observed in the existing Drosophila PD-models, which include reduced ATP levels, abnormal wing posture, shortened life span, and reduced spontaneous locomotor and climbing ability. Dopaminergic neurons seem to be more sensitive to the loss of mortalin than other neuronal sub-types and non-neuronal tissues. The loss of synaptic mitochondria is an early pathological change that might cause later degenerative events. It precedes both behavioral abnormalities and structural changes at the neuromuscular junction (NMJ) of mortalin-knockdown larvae that exhibit increased mitochondrial fragmentation. Autophagy is concomitantly up-regulated, suggesting that mitochondria are degraded via mitophagy. Ex vivo data from human fibroblasts identifies increased mitophagy as an early pathological change that precedes apoptosis. Given the specificity of the observed defects, we are confident that the loss-of-mortalin model presented in this study will be useful for further dissection of the complex network of pathways that underlie the development of mitochondrial parkinsonism

Thermally Stable Cellulose Nanocrystals toward High-Performance 2D and 3D Nanostructures

Cellulose nanomaterials have attracted much attention in a broad range of fields such as flexible electronics, tissue engineering, and 3D printing for their excellent mechanical strength and intriguing optical properties. Economic, sustainable, and eco-friendly production of cellulose nanomaterials with high thermal stability, however, remains a tremendous challenge. Here versatile cellulose nanocrystals (DM-OA-CNCs) are prepared through fully recyclable oxalic acid (OA) hydrolysis along with disk-milling (DM) pretreatment of bleached kraft eucalyptus pulp. Compared with the commonly used cellulose nanocrystals from sulfuric acid hydrolysis, DM-OA-CNCs show several advantages including large aspect ratio, carboxylated surface, and excellent thermal stability along with high yield. We also successfully demonstrate the fabrication of high-performance films and 3D-printed patterns using DM-OA-CNCs. The high-performance films with high transparency, ultralow haze, and excellent thermal stability have the great potential for applications in flexible electronic devices. The 3D-printed patterns with porous structures can be potentially applied in the field of tissue engineering as scaffolds

Bioconversion of Beetle-Killed Lodgepole Pine Using SPORL: Process Scale-up Design, Lignin Coproduct, and High Solids Fermentation without Detoxification

Mountain pine beetle killed Lodgepole pine (<i>Pinus contorta</i> Douglas ex Loudon) wood chips were pretreated using an acidic sulfite solution of approximately pH = 2.0 at a liquor to wood ratio of 3 and sodium bisulfite loading of 8 wt % on wood. The combined hydrolysis factor (CHF), formulated from reaction kinetics, was used to design a scale-up pretreatment on 2000 g wood chips at a relatively low temperature of 165 °C that reduced furan formation and facilitated high solids saccharification and fermentation. The pretreated solids and liquor were disk milled together to result in a biomass whole slurry of 25% total solids. The whole biomass slurry was directly used to conduct simultaneous enzymatic saccharification and combined fermentation (SSCombF) using a commercial cellulase and <i>Saccharomyces cerevisiae</i> YRH400 without detoxification. A terminal ethanol titer of 47.1 g L^–1 with a yield of 306 L (tonne wood)⁻¹, or 72.0% theoretical, was achieved when SSCombF was conducted at an unwashed solids loading of 18%. The lignosulfonate (LS) from SPORL was highly sulfonated and showed better dispersibility than a high purity commercial softwood LS, and therefore has potential as a directly marketable coproduct

Superflexible Wood

Flexible porous membranes have attracted increasing scientific interest due to their wide applications in flexible electronics, energy storage devices, sensors, and bioscaffolds. Here, inspired by nature, we develop a facile and scalable top-down approach for fabricating a superflexible, biocompatible, biodegradable three-dimensional (3D) porous membrane directly from natural wood (coded as flexible wood membrane) via a one-step chemical treatment. The superflexibility is attributed to both physical and chemical changes of the natural wood, particularly formation of the wavy structure formed by simple delignification induced by partial removal of lignin/hemicellulose. The flexible wood membrane, which inherits its unique 3D porous structure with aligned cellulose nanofibers, biodegradability, and biocompatibility from natural wood, combined with the superflexibility imparted by a simple chemical treatment, holds great potential for a range of applications. As an example, we demonstrate the application of the flexible, breathable wood membrane as a 3D bioscaffold for cell growth