title: Bacterium organizes hierarchical amorphous structure in microbial cellulose.
abstract: A pellicle, a gel film of microbial cellulose, is a supermolecular system containing 99% of water by weight, which is closely related to an amorphous structure in it. Using ultra-small-angle neutron scattering, in order to cover over a wide range of length scales from nm to 10 microm, we examined the hierarchical amorphous structure in the microbial cellulose, which is synthesized by a bacterium (Acetobacter xylinum). The microbial cellulose swollen by water shows small-angle scattering that obeys a power law q -behavior according to q -alpha as a function of the magnitude of the scattering vector q . The power law, determined by scattering, is attributed to a mass fractal due to the distribution of the center of mass for the crystallite (microfibril) in amorphous cellulose swollen by water. As q increases, alpha takes the values of 2.5, 1, and 2.35, corresponding, respectively, to a gel network composed of bundles, a bundle composed of cellulose ribbons, and concentration fluctuations in a bundle. From the mass fractal q -behavior and its length scale limits, we evaluated a volume fraction of crystallite in microbial cellulose. It was found that 90% of the cellulose bundle is occupied by amorphous cellulose containing water.
authors.affiliation: Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki, Tokai, Japan. koizumi.satoshi@jaea.go.jp
authors.forename: S
authors.initials: S
authors.lastname: Koizumi
authors.forename: Z
authors.initials: Z
authors.lastname: Yue
authors.forename: Y
authors.initials: Y
authors.lastname: Tomita
authors.forename: T
authors.initials: T
authors.lastname: Kondo
authors.forename: H
authors.initials: H
authors.lastname: Iwase
authors.forename: D
authors.initials: D
authors.lastname: Yamaguchi
authors.forename: T
authors.initials: T
authors.lastname: Hashimoto
mesh_terms: D002482:Cellulose / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D004798:Enzymes / Q000378:metabolism; D041822:Gluconacetobacter xylinus / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D033363:Neutron Diffraction; D011108:Polymers / Q000378:metabolism; D053838:Scattering, Small Angle
chemical_list: D004798:Enzymes; D011108:Polymers; D002482:Cellulose