SYNTHESIS OF CELLULOSE BY ACETOBACTER XYLINUM

Abstract

The transfer of the glucosyl moiety from uridine diphosphate glucose in the presence of Acetobacter xylinum cell-free extracts led to the formation of a mixture of alkali-soluble and -insoluble cellodextrins. Typical cellulose fibrils could not be detected by electron microscopy in this product. Immediately after release into the medium, cellulose formed by whole cells is in a "prefibrous" form which passes through Millipore filters of 0.45 and 0.8 # pore diameter. Non-filtrable fibrils arise from this material probably by a process of crystallization involving no cxtracellular enzymes. Fibrils formed in shaken cell suspensions intertwine and form aggregates visible to the naked eye. In quiet suspensions pcllicles arc formed which float on the surface. Soluble Na-carboxymethylccllulosc (CMC) is incorporated into cellulose fibrils formed in its presence, probably by a process of cocrystallization. Aggregation of fibrils containing CMC is delayed because of electrostatic repulsion between carboxylic groups. The aggregation time depends on the amount of CMC incorporated, its degree of substitution, the pH of the medium, and the ionic strength. The amount of CMC incorporated depends on the relative concentration CMC/ccllulose and on the similarity of the CMC and the cellulose molecules i.e. in molecular weight and the number of carboxyl substitutions. CeUulos¢ pellicles formed in the presence of CMC by unshaken cell suspensions consist of crossed, superimposed layers of parallel oriented cellulose fibrils. The same phenomenon is observed when phosphomannan, but not levan, is substituted for CMC. The biogenesis of oriented cellulose fibrils is envisaged as a process comprising the following steps: polymerization of the monomeric precursor, diffusion of the molecule to crystallization sites, crystallization, and orientation. It is proposed that charged polysaccharides play a role similar to that of CMC in affecting the orientation of cellulose fibrils in the plant cell wall.

Biobynthesis of Carboxymethylated-bacterial cellulose with coconut-water

“…This may be because the added CMC in static culture had delayed the aggregation and the crystallization of cellulose microfibrils, and resulted in the crystallite index and cellulose I content decreased. This confirmed that added polysaccharides and hemicelluloses can interact with the BC microfibrils and change its morphology [15][16][17]. …”

STRUCTURE AND DISTRIBUTION OF GLUCOMANNAN AND SULFATED GLUCAN IN THE CELL WALLS OF THE RED ALGA KAPPAPHYCUS ALVAREZII (GIGARTINALES, RHODOPHYTA)

“…Besides interconnecting functions, the sulfated glucan could also modulate cellulose assembly and control its orientation. Such effects have been inferred from results obtained with composites of cellulose synthesized by the bacterium A. xylinum in the presence of anionic or neutral cellulosic derivatives (Ben‐Hayyim and Ohad 1965, Haigler et al 1982, Yamamoto et al 1996). Additionally, the sulfated glucan may also be at the interface of cellulose fibrils and the matrix galactans.…”

Influential factors to enhance the moving rate of Acetobacter xylinum due to its nanofiber secretion on oriented templates

“…Carboxymethylcellulose sodium salt (CMC), which is known as a water soluble polysaccharide, was employed to add to the Schramm-Hestrin (SH) medium (Hestrin & Schramm, 1954) used for the cultivation of A. xylinum. The CMC could be considered as an inhibitor for self-assembly of secreted cellulose microfibrils by the surface electrostatic repulsion due to the carboxymethyl groups of attached CMC (Ben-Hayyim & Ohad, 1965;Watanabe, Gondo, & Kitao, 2004). Concerning the condition of the templates, the surface properties of NOC were modified by changing the draw ratio, and also addition of chitin as an additive.…”