Algal cellulose

Algal cellulose Algal cultures Algal gums Algiade... 

Treatment of the algal cellulose (mixture of la—IP) from Valonia in ethylenediamine to give Cellulose IIIj simultaneously induced sub fibrillation in the initial microfihril (75). Thus crystallites 20 nm wide were spHt into subunits only 3—5 nm wide, even though the length was retained. Conversion of this IIIj back to I gave a material with an electron diffraction pattern and nmr spectmm similar to that of cotton Cellulose ip. 

The considerations and interpretation of the spectra have been discussed in detail by Earl and Van der Hart13). Here we shall follow Atalla s interpretation of spectra of celluloses from various origins algal cellulose, cotton linters, ramie, and the celluloses of pure polymorphic froms I and II 17,19). The experimental spectra are given in Fig. 4. 

M. Koyama, J. Sugiyama, and T. Itoh, Systematic survey on crystalline features of algal celluloses, Cellulose, 4 (1997) 147-160. 

Cellulosic materials usually form crystal structures in part, and water cannot penetrate the inside of crystalline domains at room temperature. Native celluloses form crystalline microfibrils or bundles of cellulose chains 2-5 nm in width for higher plant celluloses and 15-30 nm for algal celluloses, which are observable by electron microscope. Almost all native celluloses have X-ray diffraction patterns of cellulose I with crystallinity indexes (Cl) 13] of about 40-95 %. 

Attention was then directed to the analysis of the spectra of algal celluloses wherein the component is the... 

VanderHart and Atalla also took advantage of the spectra derived from the acid-hydrolyzed samples of the algal cellulose to generate more highly resolved representative spectra of the and I/3 forms. These are shown in... 

On the basis of the results of electron diffraction studies by Sugiyama, Nishiyama et al undertook their very elaborate analyses of the diffraction patterns of the two forms of cellulose using X-ray, synchrotron, and neutron scattering. They also concluded that the two forms of cellulose have different unit cells, which imply that three different conformations coexist in the algal celluloses that are 60-70% of the Iq, form. This not only contradicts the clear evidence from the Raman spectra shown in Figure 9, but even more importantly is in direct conflict with the results of the lattice image studies reported earlier by Sugiyama et alJ that showed the nanofibrils of... 

Electron diffraction studies carried out on algal celluloses after the discovery of the Iq/I duality have been interpreted to indicate that the two forms may alternate along the length of individual microfihrils. These observations can also be interpreted as manifestations of the slow twisting about the long axis that has been observed in other studies of similar algal celluloses. 

The previous studies (1-3) suggested that the higher plant celluloses, like cotton and ramie, were rich in Ig while the content was appreciable if not dominant in the algal celluloses and the bacterial cellulose obtained from Acetobacter xylinum. In Figure 2 the considerable contrast between the spectra of cotton linter cellulose, both dry (2A) and wet (2B), and algal cellulose (2C) from Valonla ventricosa is Illustrated. Because the lateral... 

In this report we present experimental evidence derived from these four approaches. In the end, the hypothesis that unit cell inequivalence alone causes the observed multiplicity for chemically equivalent carbons is supported. Therefore, the crystalline composite hypothesis, although slightly revised, is strongly supported, particularly for the algal celluloses. 

Mechanical beating of an algal cellulose from Cladophora glomerata was carried out for 5 hr in a Waring blender at 1% and 3% solids consistency. Beating was judged more efficient in the latter case based on a greater retention of water. 

Spectra of Several Native Celluloses. In Figure 3 the CP-MAS spectra of several higher plant celluloses are compared and are also contrasted to the spectrum of algal cellulose from Cladophora glomerata (bottom spectrum). In Figure 4, the spectra of two samples of bacterial cellulose from two different sources of Acetobacter xylinum, several algal celluloses, and the Cladophora, beaten at 1% solids consistency, are shown. 

Figure 6 shows spectra of five preparations of algal celluloses obtained from Cladophora spectrum A is from the original purified cellulose, spectrum B is that of the same cellulose beaten in a Waring Blender for 5 h while dispersed in water at 1 solids consistency, spectrum C is like B except that the beating was carried out at 3 solids consistency, spectrum D is that of the beaten cellulose in spectrum B following acid hydrolysis in 4N HCl for 44 h at 100 C (22 mass recovery), and... 

Figure 8. CP-MAS spectra of the highly crystalline algal cellulose, Rhizoclonium hleroglyphicum as a function of proton spin locking time.

A survey of several native celluloses reinforced the similarity of the higher plant celluloses to one another, although limits of resolution and questions of chemical purity in the cellulose chains make comparison difficult and less meaningful. A parallel survey of NMR spectra from the more chemically pure algal celluloses and the bacterial cellulose, Acetobacter xylinum, indicated a general uniformity, albeit these spectra were distinct from the spectra of the higher plant celluloses. These algal cellulose spectra, however, showed small variations, outside of experimental error, which were taken as evidence for crystalline polymorphy. 

Chaln unit cell. They argued that algal celluloses consist of pure 8-chaln unit cells, whereas higher plant celluloses, like ramie, are mixtures of 2-chain and 8-chain unit cells. 

We wish to express our profound thanks to Dr. J.-F. Revol of the Pulp and Paper Research Institute of Canada for his interest, discussions, and his willingness to characterize the lateral dimensions of crystallites in certain of the algal cellulose preparations. 

Orientation. The orientation of the cellulose chain axis in a number of different fibers has been studied in detail (21-22). Much less is known about the cellulose orientation in the plane perpendicular to the chain axis. The orientation in this plane is determined by the lateral arrangement of the microfibrils relative to each other. In algal celluloses, the evidence from x-ray and electron diffraction indicates that the microfibrils are arranged nonrandomly in the plane perpendicular to the chain axis (21-29). Preston (22) proposed the model shown in Figure 1 to explain his x-ray data. There are two different orientations of the microfibrils. The 002 planes in one set of microfibrils are approximately perpendicular to the 002 planes in the second set. In both sets of micro-fibrils, the 101 planes are oriented parallel to the cell wall surface (refer to Figure 1). Preston s model has been confirmed in more recent studies (29). In the remainder of this report, the type of orientation shown in Figure 1 will be referred to as alternating orientation. 

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