Abstract
The structure of microbial cellulose (MC) produced by Acetobacter xylinum was studied in presence of Fluorescent Brightener, Direct Blue 1, 14, 15, 53, Direct Red 28, 75 and 79, as probe. X-ray diffraction pattern of the product showed that it was a crystalline complex of dye and cellulose. The product has the structure in which the monomolecular layer of the dye molecule is included between the cellulose sheets corresponding to the (\( 1\bar{1}0 \)) planes of microbial cellulose. As a result of dye inclusion, d-spacing of lower angle plane (100) of products becomes 8.0–8.8 Å instead of 6.1 Å of MC. The d-spacing for the higher angle plane must be (010) plane due to stronger van der Waals forces between the pyranose rings which reduced 5.3 Å space of (110) plane of MC to 3.9–4.5 Å in the product. However, cellulose regenerated from FB, DR28 products was cellulose I and IV, respectively, and that from each DB1, 14, 15, 53, DR75 and 79 products was cellulose II. Solid state 13C NMR and deuteration-IR showed the product was non-crystalline which was contrasted to X-ray results. The regenerated celluloses were cellulose Iβ, IVI and II, respectively. Thus the structure of the product depends on the characteristics of dye which affects the conformation of cellulose at the nascent stage by the direct interaction with cellulose chains. The different regenerated celluloses as well as different fine structure in the same cellulose allomorph were produced depending mainly on number and position of the sulfonate groups in the dye.
Highlights
Cellulose is the most abundant macromolecules produced on earth (Zhao et al 2007) and most cellulose is produced by vascular plants
The product has the structure in which the monomolecular layer of the dye molecule is incorporated between cellulose sheets corresponding to the (1"10) plane of microbial cellulose
Cellulose regenerated from Fluorescent Brightener (FB) and DR28 products is Cellulose Ib and IVI, and that from each DB1, DB14, DB15, DB53, DR75 and DR79 product is Cellulose II
Summary
Cellulose is the most abundant macromolecules produced on earth (Zhao et al 2007) and most cellulose is produced by vascular plants. MC is an exopolysaccharide produced by various species of bacteria, such as those of the genera Acetobacter, Agrobacterium, Aerobacter, Achromobacter, Azotobacter, Rhizobium, Sarcina, and Salmonella (Chawla et al 2009). Four major types of cellulose allomorphs have been reported so far, cellulose I, II, III and IV on the basis of X-ray diffraction patterns (Isogai 1994; Sarko 1978; Marchessault and Sarko 1967; Walton and Blackwell 1973; Marchessault and Sundararajan 1985). Crystal structures of cellulose allomorphs, such as unit cell sizes, packing modes of cellulose chains, conformations at Cl, C4 and C6 (rotational angles /, u and v, respectively) have been studied from as early as 1920s by X-ray diffractometry, electron microscopy, IR spectroscopy and Raman spectroscopy, and other techniques
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