WAXS and 13C NMR study of Gluconoacetobacter xylinus cellulose in composites with tamarind xyloglucan

Model composites, produced using cellulose from stationary cultures of the bacterium Gluconoacetobacter xylinus and tamarind xyloglucan, were examined by wide-angle X-ray scattering (WAXS) and CP/MAS solid-state C-13 NMR spectroscopy. The dominant crystallite allomorph of cellulose produced in culture media with or without xyloglucan was cellulose I-alpha (triclinic). The presence of xyloglucan in the culture medium reduced the cross-section dimensions of the cellulose crystallites, but did not affect the crystallite allomorph. However, when the composites were refluxed in buffer, the proportion of cellulose I-beta allomorph increased relative to that of cellulose I-alpha. In contrast, cellulose I-alpha remained the dominant form when cellulose, produced in the absence of xyloglucan, was then heated in the buffer. Hence the presence of xyloglucan has a profound effect on the formation of the cellulose crystallites by G. xylinus. (c) 2007 Elsevier Ltd. All rights reserved.