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Because of the increasing concerns related to fiber wastes resulting from non-biodegradable plastics and their impact in terms of environmental pollution, the demand for the development of biodegradable fibers has increased. Regenerated fibers of polysaccharides are expected as biomass fibers because of their biodegradability and structural variety. In this study, a linear polysaccharide synthesized by in vitro enzymatic polymerization, α-1,3-glucan, was wet-spun using 8% (w/w) lithium chloride in a dimethylacetamide solution. When ethanol (EtOH) was used in the coagulation bath, the resulting fibers were transparent, flexible, and dense, whereas the fibers produced with water in the coagulation bath were translucent, brittle, and aggregated. The former regenerated fibers exhibited tensile strength (11 cN/tex, 138 MPa), elongation at break (12%), and Young's modulus (3.5 GPa). The X-ray fiber diagram of the regenerated fibers coagulated in EtOH showed that the fibers were well-oriented along the fiber axis. The crystalline structure was determined to consist of a twofold helix with crystal lattice parameters of a = 1.59 nm, b = 0.976 nm, and c (fiber axis) = 0.852 nm.

Owing to the environmental impact of the textile industry, which distributes petroleum-based synthetic fibers on a large scale, there is a growing demand for renewable biomass-based biodegradable fiber. Curdlan, a linear β-1,3-glucan, can be potentially converted into a functional fiber with excellent sustainability and biodegradability because of its helical crystalline structure and unique physicochemical properties. Herein, we demonstrate a facile and green preparation of regenerated curdlan fibers and characterize the fiber properties via mechanical and structural analyses. Curdlan (9 wt %) in an ionic liquid (1-ethyl-3methylimidazolium acetate, [Emim][OAc]), was sequentially extruded under a mild condition at 80 °C, drawn in an air gap, and coagulated in water. The resulting fiber was transparent, soft, and had high water-absorption ability (∼86%). By changing the draw ratio from 1 to 10, the molecular orientation of the regenerated fibers increased, resulting in enhanced tenacity (5.2 ± 0.1 cN tex −1 or 75 ± 1 MPa) and Young's moduli (2.7 ± 0.1 GPa). Although the mechanical strength of these curdlan-regenerated fibers is not comparable to those of conventional cellulose-regenerated fibers, their exceptionally excellent elongation (20−50%) in the dry state is noteworthy, indicating their potential use in different applications from those desired for the cellulose fibers.

Polysaccharides are promising renewable alternatives to petroleum-based plastics, and are high-value-added materials in various industries. In this work, we synthesized dextran (α-1,6-glucan) ester derivatives substituting acyl groups with different carbon numbers from acetate to laurate. We found that the thermal stability of dextran was improved by esterification. Moreover, using differential scanning calorimetry and X-ray diffraction, we revealed that dextran ester derivatives were amorphous. Self-standing, transparent, solvent-cast films of dextran ester derivatives were prepared. Dextran ester derivatives adhered to various materials, including polyvinyl alcohol (PVA) films, wood, glass, and aluminum. In addition, the adhesive interfaces were transparent, which is important for practical applications. The adhesive strength for PVA films increased with concentration, exceeding the breaking strength of the PVA film at 0.3 g/mL. Moreover, dextran valerate and dextran hexanoate behaved as hot-melt-type adhesives. These results demonstrate the potential of dextran ester derivatives as biomass-based adhesives.

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