Chitin and chitosan: Properties and applications

https://faculty.washington.edu/renatab/courses/PSE490/downloads/pretreatment.pdf

Features of promising technologies for pretreatment of lignocellulosic biomass.

As the most important skeletal component in plants, the polysaccharide cellulose is an almost inexhaustible polymeric raw material with fascinating structure and properties. Formed by the repeated connection of D-glucose building blocks, the highly functionalized, linear stiff-chain homopolymer is characterized by its hydrophilicity, chirality, biodegradability, broad chemical modifying capacity, and its formation of versatile semicrystalline fiber morphologies. In view of the considerable increase in interdisciplinary cellulose research and product development over the past decade worldwide, this paper assembles the current knowledge in the structure and chemistry of cellulose, and in the development of innovative cellulose esters and ethers for coatings, films, membranes, building materials, drilling techniques, pharmaceuticals, and foodstuffs. New frontiers, including environmentally friendly cellulose fiber technologies, bacterial cellulose biomaterials, and in-vitro syntheses of cellulose are highlighted together with future aims, strategies, and perspectives of cellulose research and its applications.

Cellulose: Fascinating Biopolymer and Sustainable Raw Material

Chitin is the most abundant natural amino polysaccharide and is estimated to be produced annually almost as much as cellulose. It has become of great interest not only as an underutilized resource, but also as a new functional material of high potential in various fields, and recent progress in chitin chemistry is quite noteworthy. The purpose of this review is to take a closer look at chitin and chitosan applications. Based on current research and existing products, some new and futuristic approaches in this fascinating area are thoroughly discussed.

A review of chitin and chitosan applications

This critical review provides a processing-structure-property perspective on recent advances in cellulose nanoparticles and composites produced from them. It summarizes cellulose nanoparticles in terms of particle morphology, crystal structure, and properties. Also described are the self-assembly and rheological properties of cellulose nanoparticle suspensions. The methodology of composite processing and resulting properties are fully covered, with an emphasis on neat and high fraction cellulose composites. Additionally, advances in predictive modeling from molecular dynamic simulations of crystalline cellulose to the continuum modeling of composites made with such particles are reviewed (392 references).

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Cellulose nanomaterials review: structure, properties and nanocomposites

Lignin represents a vastly under-utilized natural polymer co-generated during papermaking and biomass fractionation. Different types of lignin exist, and these differ with regard to isolation protocol and plant resource (i.e., wood type or agricultural harvesting residue). The incorporation of lignin into polymeric systems has been demonstrated, and this depends on solubility and reactivity characteristics. Several industrial utilization examples are presented for sulfur-free, water-insoluble lignins. These include materials for automotive brakes, wood panel products, biodispersants, polyurethane foams, and epoxy resins for printed circuit boards.

Recent Industrial Applications of Lignin: A Sustainable Alternative to Nonrenewable Materials

The viscoelastic properties of mod were investigated using dynamic mechanical thermal analysis and differential scanning calorimetry. Under a limited set of conditions, two separate glass transitions (T
 g) could be identified with both techniques. These two transitions were identified as arising from the amorphous lignin and hernicellulose matrix in the wood cell wall. Moisture dramatically affected the temperature at which the two dispersions occurred and, consequently, the ability to resolve their independent responses. The relationship betweenT
 g and moisture for both components could be modelled with the Kwei equation, which accounts for the presence of secondary interactions. Annealing and specific interactions of a series of organic diluents were wed in an attempt to enhance the resolution of the two components values ofT
 g. Time-temperature superposition was shown to be applicable to wood plasticized with ethyl formamide, following Williams-Landel-Ferry behaviour over the temperature rangeT
 g toT
 g + 85° C. These observations allow certain conclusions to be drawn concerning the applicability of existing models of the wood cell wall's supermolecular morphology. Most notably, models of thein situ morphology of the three wood components can be limited to those which consider the amorphous matrix of lignin and hemicellulose to be immiscible.

Relaxation behaviour of the amorphous components of wood

Separation, characterization and hydrogel-formation of hemicellulose from aspen wood.

The impact of lignins of various origins on filter paper hydrolysis by fungal cellulase was evaluated. Powdered lignins were added to enzyme incubations, either as isolated or after thorough hydroxypropylation of phenolic sites. Extent of cellulose hydrolysis was reduced by 14−60% by the addition of up to 15% lignin to the substrate. Unmodified lignins were more detrimental to cellulose hydrolysis than hydroxypropylated lignins. The inhibitory effect of lignin addition was only partially overcome by a 10-fold increase in cellulase activity, suggesting inhibitory lignin interactions with both substrate and enzyme. Preincubation of cellulase with underivatized lignins resulted in reduced enzyme activity and soluble protein concentration in the supernatant, suggesting protein precipitation with lignin rather than reduced activity of a lignin−enzyme complex as the inhibitory mechanism. Two further experiments showed that the negative impact of lignin on cellulose hydrolysis can be counteracted by addition of ...

Lignin Impact on Fiber Degradation. 3. Reversal of Inhibition of Enzymatic Hydrolysis by Chemical Modification of Lignin and by Additives

This books reports on lignins, irregular phenylpropane biopolymers that make up approximately 20-30% of the available polymeric content of hardwood tree stems. In plants, lignin is second in natural abundance only to cellulose. This material offers, therefore, a valuable resource that must be utilized if the full value of harvested tree crops is to be attained. The yearly growth of the world forests is about 7-9 billion cubic meters of biomass. During the production of 140 million tons of cellulose and pulp from a part of this biomass, about 50 million tons of lignin are formed. Over 95% of the lignin is used as an energy source to operate pulping mills.

Wolfgang G. Glasser

Papers

Recent Industrial Applications of Lignin: A Sustainable Alternative to Nonrenewable Materials

Relaxation behaviour of the amorphous components of wood

Separation, characterization and hydrogel-formation of hemicellulose from aspen wood.

Lignin Impact on Fiber Degradation. 3. Reversal of Inhibition of Enzymatic Hydrolysis by Chemical Modification of Lignin and by Additives

Lignin: properties and materials.