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To establish a sustainable material production system and preserve the Earth’s environment, “biomass plastics” that are made from renewable biomass instead of petroleum and “biodegradable plastics” that are completely degraded into carbon dioxide and water by enzymes secreted by microorganisms in the environment are desirable products. This miniature review describes a series of studies on microbial polyesters and polysaccharide ester derivatives, including the synthesis of novel polymers, development of new processing techniques for high-performance films and fibers, elucidation of the relationship between structure and properties using synchrotron radiation, and control of the rate of enzymatic degradation.To establish a sustainable material production system and preserve the Earth’s environment, “biomass plastics” that are made from renewable biomass instead of petroleum and “biodegradable plastics” that are completely degraded into carbon dioxide and water by enzymes secreted by microorganisms in the environment are desirable products. This miniature review describes a series of studies on microbial polyesters and polysaccharide ester derivatives, including the synthesis of novel polymers, development of new processing techniques for high-performance films and fibers, elucidation of the relationship between structure and properties using synchrotron radiation, and control of the rate of enzymatic degradation.

Regenerated fibers have garnered considerable attention in the textile industry because of their inherent biocompatibility and biodegradability. Polysaccharides are abundant renewable biomass resources, and their structural diversity depends on the constituent monosaccharides and linkage styles; thus, the resultant fibers can exhibit a wide range of performance and functions. However, most conventional studies and applications have only focused on β-1,4-glucan (cellulose), and other polysaccharides have not been fully explored. This focus review covers two specific polysaccharides: β-1,3-glucan (curdlan) and α-1,3-glucan. In particular, their characteristic fiber properties are introduced with insights related to the different structures of crystalline and molecular chains. Moreover, the appropriate parameters for dry-jet wet spinning of these polysaccharides are described, such as the concentration of the dope, the appropriate spinning and coagulation solvents for each polysaccharide, and the post-treatment method for the regenerated fibers.Regenerated fibers of β-1,3-glucan (curdlan) and α-1,3-glucan were fabricated by dry-jet wet spinning, and the fiber properties and structures are summarized in this review. The flexible and water-absorbent curdlan and the stiff and strong α-1,3-glucan would be utilized in different applications from conventional cellulose. As a new type of post-treatment, a two-step stretching method in water was developed for α-1,3-glucan by utilizing its crystal transition. This can be applied to various polysaccharides for future production of high-performance 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.

This study probed in vitro the mechanisms of competition/coexistence between Streptococcus sanguinis (known for being correlated with health in the oral cavity) and Streptococcus mutans (responsible for aciduric oral environment and formation of caries) by means of quantitative Raman spectroscopy and imaging. In situ Raman assessments of live bacterial culture/coculture focusing on biofilm exopolysaccharides supported the hypothesis that both species engaged in antagonistic interactions. Experiments of simultaneous colonization always resulted in coexistence, but they also revealed fundamental alterations of the biofilm with respect to their water-insoluble glucan structure. Raman spectra (collected at fixed time but different bacterial ratios) showed clear changes in chemical bonds in glucans, which pointed to an action by Streptococcus sanguinis to discontinue the impermeability of the biofilm constructed by Streptococcus mutans. The concurrent effects of glycosidic bond cleavage in water-insoluble α − 1,3–glucan and oxidation at various sites in glucans’ molecular chains supported the hypothesis that secretion of oxygen radicals was the main “chemical weapon” used by Streptococcus sanguinis in coculture.

This study probed in vitro the mechanisms of competition/coexistence between Streptococcus sanguinis (known for being correlated with health in the oral cavity) and Streptococcus mutans (responsible for aciduric oral environment and formation of caries) by means of quantitative Raman spectroscopy and imaging. In situ Raman assessments of live bacterial culture/coculture focusing on biofilm exopolysaccharides supported the hypothesis that both species engaged in antagonistic interactions. Experiments of simultaneous colonization always resulted in coexistence, but they also revealed fundamental alterations of the biofilm with respect to their water-insoluble glucan structure. Raman spectra (collected at fixed time but different bacterial ratios) showed clear changes in chemical bonds in glucans, which pointed to an action by Streptococcus sanguinis to discontinue the impermeability of the biofilm constructed by Streptococcus mutans. The concurrent effects of glycosidic bond cleavage in water-insoluble α − 1,3-glucan and oxidation at various sites in glucans' molecular chains supported the hypothesis that secretion of oxygen radicals was the main \"chemical weapon\" used by Streptococcus sanguinis in coculture.

Polyphosphate (polyP) is one of the most conserved biomacromolecules and can form aggregates, such as polyP granules in bacteria, which are generated through liquid–liquid phase separation (LLPS). Studies have examined the mechanism of polyP aggregation using LLPS systems containing artificial polyP molecules as aggregation system models, where LLPS is typically induced by multivalent salts and polyelectrolytes. Although the typical concentrations of monovalent ions in living cells are approximately 100 times higher than those of divalent ions, the effects of monovalent ions on the LLPS of polyP solutions are little known. This study demonstrated that submolar NaCl induces LLPS of polyP solutions, whereas other monovalent salts did not at the same concentrations. Small-angle X-ray scattering measurements revealed that NaCl significantly stabilizes the intermolecular association of polyP, inducing LLPS. These findings suggest that the modulation of monovalent ion concentrations is an underlying mechanism of polyP aggregate formation/deformation within living cells.