IN-SITU CRYSTALLIZATION OF BACTERIAL CELLULOSE .1. INFLUENCES OF POLYMERIC ADDITIVES, STIRRING AND TEMPERATURE ON THE FORMATION CELLULOSES I-ALPHA AND I-BETA AS REVEALED BY CROSS-POLARIZATION MAGIC-ANGLE-SPINNING (CP/MAS) C-13 NMR-SPECTROSCOPY

To obtain further information about the formation of cellulose I-alpha and I-beta, cross polarization/magic angle spinning (CP/MAS) C-13 NMR spectroscopy was used to study the effects of polymeric additives, stirring and culture temperature on the I-alpha fraction for cellulose from cultures of Acetobacter xylinum. When xyloglucan (XG) or carboxymethyl cellulose sodium salt (CMC) was added to the incubation medium, the amount of cellulose I alpha decreased markedly, from a normal level of 64% to as low as 30%, with the most additive giving the lowest levels of I-alpha. Moreover, stirring causes mixtures containing even small amounts of XG to have a large effect. These results suggest that CMC or XG interferes with the aggregation of fibrillar units into the normal ribbon assemblies. It may be that there is a strain associated with this aggregation that results in the higher-energy I-alpha form. Thus, cellulose I-beta may grow preferentially when the strain caused by aggregation is not present. Lower temperatures (36-10 degrees C) gave an increase in I-alpha (from 56 to 72%).