Bacterial cellulose crystal surfaces

Iwata et al. (27) observed by X-ray analysis that out of different glucans, xylans and galactans, it was indeed the mannans that showed the highest affinity towards bacterial cellulose. The sorption mechanism of different hemicelluloses is, moreover, not necessarily the same. Uhlin et al (28) found that bacterial cellulose crystallized in a different form in the presence of wood hemicelluloses than in their absence (Ip, rather than Iq). Furthermore, xylans and mannans seemed to interact with cellulose in different ways - xylans co-crystallized with cellulose producing defects in the crystalline structure, while mannans mainly decreased the crystallite size and thus also the over all degree of crystallinity. Xylan and mannan chains have been shown to undergo different conformational transitions upon sorption (29). The mannans were able to form a two-fold helix and lay down on the cellulose chain quite nicely and seemed to interact with two cellulose chains, while xylan took on a three-fold molecular axis and could, therefore, not sorb as efficiently. Larsson et al (30) showed through solid-state NMR analysis that xylans can, anyhow, interact directly with cellulose surfaces. Tetramers were the smallest polymers to sorb onto cellulose surfaces (29). 

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