The formation of Gluconacetobacter xylinum cellulose under the influence of the dye brilliant yellow

Abstract

The structural characteristics of the nascent fibril produced by Gluconacetobacter xylinum (G. xylinum) have been studied under the influence of the cellulose binding dye brilliant yellow (BY) by wide angle X-ray diffraction (WAXD), Fourier transform infrared spectroscopy (FTIR) and 13C solid-state nuclear magnetic resonance. BY is found to be more effective at reducing crystallinity than fluorescent brightener 28 (FB28), pontamine fast scarlet 4 (S4B) and other dyes previously studied. Under static cultivation conditions, increasing concentrations of brilliant yellow in the growth media from 20, 50, 100 to 250 μM, result in decreasing cellulose crystallinity from 73 to 18%, respectively, as compared to 82% exhibited by the control. FTIR data indicate that the presence of BY is most effective at suppressing intra-molecular hydrogen bonding. After boiling in 70 vol% aqueous EtOH solution for 12 h, the extracted dye-altered cellulose becomes more ordered, which may be due to the extraction of BY from the BY-cellulose complex. FTIR data indicate that compared to control cellulose, the reclaimed brilliant yellow-altered cellulose contains more cellulose Iβ, where the FB28 and S4B altered cellulose remains principally Iα. Based on WAXD and NMR data we propose a dye-cellulose complex structure associated with BY. This model supports the hypothesis that microfibrils assemble through the hydrogen bonding of formed mini-sheets that consist of stacked glucan chains linked by van der Waals forces.