Eur. Phys. J. E (2008) 26: 137-142
https://doi.org/10.1140/epje/i2007-10259-3

ISMC-2007

Bacterium organizes hierarchical amorphous structure in microbial cellulose

¹ Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Tokai, Japan
² Bio-Architecture Center and Graduate School of Bioresource and Bioenviromental Sciences, Kyushu University, Fukuoka 812-8581, Fukuoka, Japan

^* e-mail: koizumi.satoshi@jaea.go.jp

Received: 31 October 2007
Accepted: 19 December 2007
Published online: 3 March 2008

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 10μm, 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 ^-α 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, α 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.