An aerobic, Gram-negative bacterium, Gluconacetobacter xylinus, was successfully employed to produce a stretchable cellulose nanofiber pellicle using dissolved oxygen in a conventional cultured medium. The obtained nanofibers were highly crystalline with the metastable cellulose Iα phase being apparently the dominant phase by more than 90%. The obtained pellicle could be stretched by up to 1.5 times to provide oriented crystalline nanofibrous films. Low heating of the nanofibrous film induced the transformation of the dominant cellulose Iα crystalline phase into the Iβ crystalline phase without a loss of crystallinity or the high Young's modulus. The film also exhibited unique and anisotropic viscoelastic and mechanical properties as well as superior thermal stability compared with conventional high-performance synthetic polymeric materials. In addition, when G. xylinus cells were transferred to the oriented surface after stretched, they started to synthesize cellulose ribbons that parallel the nanofiber orientation of the substrate. This function as a template was evidenced by direct video imaging of the motion of the bacteria. The application of a bacterial culture using dissolved oxygen in the medium offers the fabrication of novel anisotropic and nanofibrous scaffold of cellulose Iα.
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