Cellulose formation

There are several schemes for the synthesis of cellulose formates (slow) reaction of the polymer with formic acid faster reaction in the presence of a mineral acid catalyst, e.g., sulfuric or phosphoric acid. The latter route is usually associated with extensive degradation of the polymer chain. Reaction of SOCI2 with DMF produces the Vilsmeier-Haack adduct (HC(Cl) = N (CH3)2C1 ) [145]. In the presence of base, cellulose reacts with this adduct to form the unstable intermediate (Cell - O - CH = N" (CH3)2C1 ) from which cellulose formate is obtained by hydrolysis. The DS ranges from 1.2 to 2.5 and the order of reactivity is 5 > C2 > C3 [140-143,146]. 

Cellulose formate, manufacture, 5 418 Cellulose heptylate, moisture properties, 5 416t... 

Plant cell walls are complex, heterogeneous structures composed mainly of polymers, such as cellulose, hemicelluloses, and lignins. In spite of several decades of research, cell wall assembly and the biosynthesis and ultimate biodegradative pathways of individual polymers are still far from being fully understood. One simple example will suffice Even today, no enzyme capable of catalyzing cellulose formation in vitro has been obtained. 

Tobacco primary cell wall and normal bacterial Acetobacter xylinum cellulose formation produced a 36.8 3A triple-stranded left-hand helical microfibril in freeze-dried Pt-C replicas and in negatively stained preparations for transmission electron microscopy (TEM). A. xylinum growth in the presence of 0.25 mM Tinopal disrupted cellulose microfibril formation and produced a... 

Coumarin (2H-l-benzopyran-2-one) is a known inhibitor of cellulose formation,355-357 and Hopp and coworkers358 found that, in membranes from the alga Prototheca zopfii, it inhibits the transfer in vitro of the lipid-linked cello-oligosaccharide to its protein acceptor (see Section II,2,b). 

These products are characterized in terms of moles of substitution (MS) rather than DS. MS is used because the reaction of an ethylene oxide or propylene oxide molecule with cellulose leads to the formation of a new hydroxyl group with which another alkylene oxide molecule can react to form an oligomeric side chain. Therefore, theoretically, there is no limit to the moles of substituent that can be added to each D-glucopyranosyl unit. MS denotes the average number of moles of alkylene oxide that has reacted per D-glucopyranosyl unit. Because starch is usually derivatized to a considerably lesser degree than is cellulose, formation of substituent poly(alkylene oxide) chains does not usually occur when starch is hydroxyalkylated and DS = MS. 

However, other workers claim that UDP-D-glucose may also be an effective donor for cellulose formation with preparations from higher plants, but we could not substantiate their results in our laboratory. 

Gluconacetobacter xylinus to optimize cellulose formation on the laboratory-scale [12]. As a result of systematic and comprehensive research over the last 10-15 years, broad knowledge of the formation and structure of BC has been acquired. This work is an important part of the integration of biotechnological methods into polysaccharide chemistry and the development of cellulose products with new properties and application potential. 

Bacteriological culture media, dulcitol, mannitol and sorbitol in, I, 192 Bacterium amylobacter, in fermentation of wood sugars, IV, 184 Bacterium dysenteries, antigens, II, 199 Bacterium xylinoides, cellulose formation by, II, 206... 

It is natural that with the growing interest in cellulose acetate, chemists have investigated other organic cellulose esters. Cellulose formate, the ester of the lowest member of the fatty acid series, has been studied. sufficiently to show that it is unlikely to be of commercial im-portance. It is difficult to produce a high degree of esterification of cellulose with this acid, and the ester which is obtained is very limited in solubility, and is highly unstable toward moisture and elevated temperatures. 

NH2), pK2 6.4 (P04 ). Purification can be carried out by passage through a DEAE-cellulose formate column, then through a Dowex 50 (H+) column to remove Na ions, concentrated by lyophilisation and redissolved in H2O. It is commercially available as a solution of 0.05g/mL of H2O. The concentration of acetoacetylcoenzyme A is determined by the method of Stem et al. [J Biol Chem 221 15 1956]. It is stable at pH 7-7.5 for several hours atO (half-life ca l-2hours). At room temperature it is hydrolysed in ca l-2hours at pH 7-7.5. At pH 1.0/20° it is more stable than at neutrality. A solution of the trisodium salt (0.05g/mL H2O) adjusted to pH 5 with 2N NaOH can be stored frozen for several weeks. It is stable at pH 2-3/-17° for at least 6 months. [Hersch Jencks J Biol Chem 242 3468 1967, Clikenbeard et al. J Biol Chem 250 3108 1975, Simon Shemin J Am Chem Soc 75 2520 1953, Moffatt KhoranaSl 1265 1959, Salem et al. Biochem J 258 563 1989, Beilstein 26 III/IV 3668.]... 

Figure 4. Cellulose formation by Ps. fluorescens in a C-supply controlling culture using cellobiose as carbon source...

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