ABSTRACT
In this study, fermentable sugars and cellulose nanocrystals (CNCs) were co-produced from endoglucanase treatment of wood pulp, followed by acid hydrolysis. Enzymatic hydrolysis was performed using two endoglucanases differentiated by the presence or absence of a cellulose-binding domain (CBD). The enzyme with an intact CBD gave the higher glucan conversion (up to 14.1 ± 1.2 wt %) and improved the degree of crystallinity of the recovered wood pulp fiber (up to 83.0 ± 1.0%). Thus, this endoglucanase-assisted treatment successfully removed amorphous content from the original cellulosic feedstock. CNC recovery (16.9 ± 0.7 wt %) from the feedstock going into the acid hydrolysis was improved relative to untreated pulp (13.2 ± 0.6 wt %). The mass loss from enzymatic treatment did not cause a decrease in the CNC yield from the starting material. The characteristics of CNCs obtained through acid hydrolysis (with or without enzyme treatment of pulp) were analyzed using X-ray diffraction, transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and differential scanning calorimetry as characterization techniques. The CNCs generated through acid hydrolysis of endoglucanase-treated wood pulp displayed comparable properties relative to those generated using untreated pulp. Thus, endoglucanase treatment can enable co-production of CNCs and sugars for biofuel fermentation.
ABSTRACT
Integrating enzymatic treatment and acid hydrolysis potentially improves the economics of cellulose nanocrystal (CNC) production and demonstrates a sustainable cellulosic ethanol co-generation strategy. In this study, the effect of enzymatic treatment on filter paper and wood pulp fibers, and CNCs generated via subsequent acid hydrolysis were assessed. Characterization was performed using a pulp quality monitoring system, scanning and transmission electron microscopies, dynamic light scattering, X-ray diffraction, and thermogravimetric analysis. Enzymatic treatment partially reduced fiber length, but caused swelling, indicating simultaneous fragmentation and layer erosion. Preferential hydrolysis of less ordered cellulose by cellulases slightly improved the crystallinity index of filter paper fiber from 86% to 88%, though no change was observed for wood pulp fibre. All CNC colloids were stable with zeta potential values below -39 mV and hydrodynamic diameters ranging from 205 to 294 nm. Furthermore, the temperature for the peak rate of CNC thermal degradation was generally not affected by enzymatic treatment. These findings demonstrate that CNCs of comparable quality can be produced from an enzymatically-mediated acid hydrolysis biorefining strategy that co-generates fermentable sugars for biofuel production.
ABSTRACT
The discotic molecule 4-chloro-2,6-bis(octadecylamino)-pyrimidine-5-carbaldehyde, displays gelation behavior in dodecane, heptane, chloroform, and dichloromethane. The aggregation behavior of this material was studied by dynamic light scattering, differential scanning calorimetry, scanning electron microscopy, polarized optical microscopy, small-angle X-ray diffraction, and wide-angle X-ray diffraction techniques. Combined with molecular modeling calculations, Fourier transform infrared, and 1H NMR studies, we propose a mechanism for the self-assembly of this fibrous lamellar architecture. Notably, we have shown that the fibers grow via stacking interactions along their main axis, via hydrogen bonding along their short axis, and via van der Waals interactions (lamellae) along the third axis. This type of morphology is desirable since it provides an opportunity to synthetically control and optimize mechanical, electrical, optical, and transport properties along the length of the fiber.
ABSTRACT
Understanding the optimal processing conditions for the fabrication of polymer nanocomposites is of fundamental importance in designing materials with balance of properties. To understand these conditions in the case of maleic anhydride grafted polypropylene (PP-g-MA)/layered mesostructured silica (LMS) nanocomposites, the effect of temperature, shear rate, and residence time during processing on the structure of the nanocomposites were studied. The results showed that the combination of temperature, residence time, and mechanical shears have strong effect on the structure of the nanocomposites, rather than just interfacial interactions between the polymer matrix and silicate layers. However, interfacial interactions between the polymer matrix and silicate layers primarily play an important role to the intercalation of polymer chains into the silicate galleries. On the basis of our experimental results, a first explanation of the formulation mechanism of PP-g-MA/LMS nanocomposites is proposed. Finally, a general concept of processing conditions for manufacturing of polymer nanocomposites by melt-compounding process in a batch-mixer is described.
