In-depth characterization of the aggregation state of cellulose nanocrystals through analysis of transmission electron microscopy images.

Dispersion of cellulose nanocrystals (CNCs) is of utmost importance to guarantee their reliable application. Nevertheless, there is still no consensual method to characterize CNC aggregation. The hypothesis of this paper is that dispersion could be quantified through the classification of aggregates detected in transmission electron microscopy images. k-Means was used to classify image particulate elements of five CNC samples into groups according to their geometric features. Particles were classified into five groups according to their maximum Feret diameter, elongation, circularity and area. Two groups encompassed the most application-critical aggregates: one integrated aggregates of high complexity and low compactness while the other included elongated aggregates. In addition, the characterization of CNC dispersion after different levels of sonication was achieved by assessing the change in the number of elements belonging to each cluster after sonication. This approach could be used as a standard for the characterization of the aggregation state of CNCs.

A Halotolerant Endo-1,4-ß-Xylanase from Aspergillus clavatus with Potential Application for Agroindustrial Residues Saccharification.

The use of non-potable water (such as seawater) is an attractive alternative for water intensive processes such as biomass pretreatment and saccharification steps in the production of biochemicals and biofuels. Identification and application of halotolerant enzymes compatible with high-salt conditions may reduce the energy needed for non-potable water treatment and decrease waste treatment costs. Here we present the biochemical properties of a halotolerant endo-1,4-ß-xylanase produced by Aspergillus clavatus in submerged fermentation, using paper sludge (XPS) and sugarcane bagasse (XSCB), and its potential application in the hydrolysis of agroindustrial residues. The peptide mass fingerprint and amino acid sequencing of the XPS and XSCB enzymes showed primary structure similarities with an endo-1,4-ß-xylanase from Aspergillus clavatus (XYNA_ASPCL). Both enzyme preparations presented good thermal stability at 50 °C and were stable over a wide range of pH and Vmax up to 2450 U/mg for XPS. XPS and XSCB were almost fully stable even after 24 h of incubation in the presence of up to 3 M NaCl, and their activity were not affected by 500 mM NaCl. Both enzyme preparations were capable of hydrolyzing paper sludge and sugarcane bagasse to release reducing sugars. These characteristics make this xylanase attractive to be used in the hydrolysis of biomass, particularly with brackish water or seawater.

Effect of drying methods on the powder and compaction properties of microcrystalline cellulose derived from Gossypium herbaceum

The effect of drying method, a process variable, on the powder and compaction properties of microcrystalline cellulose (MCC) obtained from the partial acid hydrolysis of bleached alpha (α) cellulose content of matured linters of Gossypium herbaceum (GH) was investigated. A portion of the wet MCC obtained was fluid bed dried at 60 ± 1 ºC, inlet air of 30 m3 min-1 for 3 h (coded MCC-GossF). The second portion was lyophilized at - 45 ± 2 ºC for 6 h (coded MCC-GossL). The physicochemical, scanning electron micrographs, X ray diffraction patterns and micromeritic properties of the derived MCCs were determined using standard methods. The cohesiveness and compactibility of the powders were investigated using Kawakita model while the deformation and compressibility pattern were determined using Heckel model. Avicel® PH 102 (AV-102) was used as comparing standard. Ash values of < 2%, pH (6.54 ± 0.23 to 6.58 ± 0.08), degree of polymerization, DP (231.50) was obtained. MCC-GossF had higher moisture content, swellability, better flow indices, and lesser porosity than MCC-GossL. Kawakita model demonstrated good consolidation and compactibility for both powders. Compacts of MCC-GossL were significantly (p < 0.05) harder than those of MCC-GossF. Heckel analysis demonstrated good compressibility and deformation pattern that was comparable with AV-102. Compacts of MCC-GossL had better mechanical and tablet compression properties than MCC-GossF

Characterization of Developmental Immature Fiber ( im) Mutant and Texas Marker-1 (TM-1) Cotton Fibers Using Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy.

The immature fiber ( im) mutant is one type of cotton fiber mutant with unique characteristics of non-fluffy cotton bolls. Compared to its near-isogenic wild type Texas Marker-1 (TM-1), im fiber has a thin secondary cell wall and is less mature. In this work, we applied the previously proposed principal component analysis (PCA) and simple algorithms to analyze the attenuated total reflection Fourier transform infrared (ATR FT-IR) spectra of developmental im and TM-1 fibers. The results from these approaches could not effectively and consistently indicate the inherent difference between TM-1 and im fibers at the same developmental stage. The difference between TM-1 and corresponding im fibers was detected when comparing the normalized intensity variations of the 730 cm-1 bands. The 730 cm-1 band intensities in developmental im fibers are temporally lower than those in developmental TM-1 fibers although they became similar when the TM-1 and im fibers are fully mature. The observation might imply the likelihood of temporal reduction of amorphous regions in developmental im fibers rather than in developmental TM-1 fibers.

Binding specificity and thermodynamics of cellulose-binding modules from Trichoderma reesei Cel7A and Cel6A.

In this work, Family 1 cellulose binding modules CBMCel7A and CBMCel6A were heterologously expressed and purified from Escherichia coli , and the binding properties between these CBMs and cellulose substrates were studied. Cellulose nanowhiskers (CNWs, the crystalline portion of cellulose), microcrystalline cellulose Avicel PH101 (partially crystalline cellulose), and phosphoric acid swollen cellulose (PASC, amorphous cellulose) were used as representative models for cellulose to better understand the binding interactions between the CBMs and different regions of native cellulose. Isothermal titration calorimetry (ITC) was combined with adsorption-isotherm experiment to analyze the thermodynamics of CBM binding to various cellulose substrates. N2 adsorption and static light scattering (SLS) data were used to estimate the accessible surface area of cellulose which was then used for ITC data analysis. A new method of determining the cellulose molarity based on the available surface area for CBM binding was developed, which allows different cellulose substrates to be compared for binding experiments. The ITC results showed that the binding constant (Ka) to crystalline CNWs was ∼10(5) M(-1) for CBMCel7A, while ∼10(6) M(-1) for CBMCel6A, suggesting a higher binding affinity of CBMCel6A to CNWs. For Avicel, lower binding constants for both CBMs were observed, and weak bindings to PASC were characterized, suggesting that the binding between CBMCel7A,Cel6A and cellulose to some extent relates to the crystallinity of cellulose. Additionally, the binding reactions were driven by a favorable enthalpy change, offset partially by an unfavorable entropy change. It is suggested that CBMCel6A preferentially binds to the reducing end of cellulose chain, while CBMCel7A does not show such end binding specificities. Cello-oligosaccharides less than two glucose units did not bind with CBMs, and improved binding affinities were observed for cello-oligosaccharides with longer glucose units.

Effect of cellulase mole fraction and cellulose recalcitrance on synergism in cellulose hydrolysis and binding.

Elucidating the molecular mechanisms that govern synergism is important for the rational engineering of cellulase mixtures. Our goal was to observe how varying the loading molar ratio of cellulases in a binary mixture and the recalcitrance of the cellulose to enzymatic degradation influenced the degree of synergistic effect (DSE) and degree of synergistic binding (DSB). The effect of cellulose recalcitrance was studied using a bacterial microcrystalline cellulose (BMCC), which was exhaustively hydrolyzed by a catalytic domain of Cel5A, an endocellulase. The remaining prehydrolyzed BMCC (PHBMCC) was used to represent a recalcitrant form of cellulose. DSE was observed to be sensitive to loading molar ratio. However, on the more recalcitrant cellulose, synergism decreased. Furthermore, the results from this study reveal that when an exocellulase (Cel6B) is mixed with either an endocellulase (Cel5A) or a processive endocellulase (Cel9A) and reacted with BMCC, synergism is observed in both hydrolysis and binding. This study also revealed that when a "classical" endocellulase (Cel5A) and a processive endocellulase (Cel9A) are mixed and reacted with BMCC, only limited synergism is observed in reducing sugar production; however, binding is clearly increased by the presence of the Cel5A.

Application of multidimensional scaling to preformulation sciences: a discriminatory tool to group microcrystalline celluloses.

Pre-formulation studies constitute the first step of any pharmaceutical product development and manufacture. Establishment of a comprehensive library of critical physical, chemical, biological and mechanical properties of all materials used for a formulation can be costly, tedious and time consuming, despite its importance in quality manufacturing management. This study seeks to demonstrate the pharmaceutical application of multidimensional scaling (MDS) by incorporating it as a pre-formulation tool for grouping an expanded range of microcrystalline celluloses (MCC). MDS presents the various MCC grades in two-dimensional space based on their torque rheological properties; thus conferring an extra dimension to the pre-formulation tool to facilitate the visualization of the relative positions of each MCC grade. Through this work, the utility of MDS for expediting pre-formulation studies, in particular, grouping of excipients that are available in different brands and grades can be amply exemplified.

Temperature effect in the production of multiple xylanases by Aspergillus fumigatus.

This work has evaluated the temperature effect in the production of multiple xylanases by a locally isolated strain of Aspergillus fumigatus Fresenius. Three isoenzymes, identified as xylanases I, II, and III with apparent molecular weight of 45.7 KDa, 39.8 KDa and 18.2 KDa, respectively, were produced in cultures developed at 30 degrees C and at 42 degrees C. The pattern of distribution of xylanase activity among the three isoenzymes was greatly affected by the growth temperature: at 30 degrees C, the total xylanase activity was distributed homogeneously among the three enzymes, while at 42 degrees C, the total xylanase activity was mainly due to the fractions with the highest MW (I and II) and the xylanase III was a minor component.

Cellulose-degrading potentials and phylogenetic classification of carboxymethyl-cellulose decomposing bacteria isolated from soil.

In a previous study, culturable carboxymethyl-cellulose (CMC) decomposing soil bacteria isolated from different sampling positions across an agricultural encatchment have been classified into 31 pattern groups by digestion of amplified 16S rDNA using a single restriction enzyme (Ulrich and Wirth: Microb. Ecol. 37, 238-247, 1999). In order to reveal relationships between phylogenetic diversity and phenotypic functions, a further differentiation of two selected site-specific pattern groups (I and H) was performed, resulting in a sub-classification of four and three ARDRA groups, respectively. Based on sequencing a representative isolate of each ARDRA group, the isolates were assigned to the genus Streptomyces. The ARDRA groups were dispersed across various clades of the genus with a direct affiliation to species known for cellulolytic activity in one group, only. The isolates differed in potentials to degrade colloidal, native or highly crystalline cellulose derivatives. Out of 39 isolates, 11 were capable of degrading all substrates, 17 were restricted to degrade CMC only, and 11 were active decomposers of exclusively both CMC and colloidal cellulose. In most cases, the genetic classification of the isolates corresponded with groupings based on cellulose degrading capabilities. Thus, isolates of four ARDRA groups were restricted to the degradation of CMC, while two further isolates which efficiently degraded all cellulose derivatives formed two separate ARDRA groups. The major ARDRA group, however; displayed a high variability of degradation capabilities. The study of additional phenotypic features revealed a broad potential to decompose a set of various carbon substrates, which matched the phylogenetic classification in several cases.

Comparative tablet and rheological properties of new microcrystalline cellulose: direct compression and wet granulation methods.

The overall objective of this study was to compare the rheological properties and tablet characteristics of two new varieties of celluloses (Vivacel 101 and 102), recently produced and commercialized, with the classical varieties of celluloses (Avicel and Elcema). The results showed no significant differences in the rheological properties of Vivacel and Avicel, while significant differences were found between the two celluloses and Elcema. Furthermore, there were no statistically significant differences in the disintegration times and Td values of Vivacel and Avicel. In conclusion, it was found that these new celluloses offer all the known advantages of Avicel.

Dietary fibers: their definition and nutritional properties.

Fiber is a variable material with respect to its nutritional qualities depending upon its composition and physical properties. Biological properties possessed by one type of fiber might not be shared by another type. Separate methods are required to describe quantity, composition, and quality of fiber in foods. Fibers can be generally classified into three groups: vegetable fibers, which are highly fermentable with low indigestible residue; brans, which are less fermentable; and chemically purified fibers such as wood cellulose, which are relatively unfermentable. A class of soluble substances including pectins and gums may not be true fibers, but are considered part of the dietary fiber complex because of the similar effects they can elicit in the diet. A major need is the replacement of the crude fiber method, the present official method, which is seriously defective. Since crude fiber values are erratic and poorly related to the true fiber value of food, a second major need is the reanalysis of all foodstuffs by appropriate methods and the replacement of standard tables of food composition. Accomplishment of these purposes will require more support and promotion than is presently being received.