Single crystals and oriented crystallization of ivory nut mannan

Abstract

SynopsisThe preparation of lamellar single crystals of mannan[poly((l -4)-P-D-mannose)] is described. Electron diffractograms clearly identify the perpendicular orientation of the chain axis with respect to the lamellar surface. Since the degree of polymerization is 40 or less, no conclusion is made as to chain folding. The unit cell corresponds to the mannan I structure derived from x-ray fiber data on oriented algal mannan. The baseplane dimensions found were a = 7.22 8 and b = 8.92 8, and the systematic absences observed confirm the proposed P212121 group. It was found that cellulose microfibrils from Valonia uentricosa and bacterial cellulose could serve as extended chain nuclei for inducing oriented crystallization of mannan on cellulose. This produces a shish-kebab type of morphology.

13C CP/MAS NMR spectra of poly-β-D(1 → 4) mannose: mannan

“…The first sample is a pure mannan I as shown by X-ray powder diffraction and has been used in previous work (3,7). Additionally, a whole ivory nut was mounted on a lathe and turned down into a cylinder for direct insertion in the rotor.…”

“…It has been shown that these so-called hemicelluloses are oriented parallel to the microfibrils (2) but there is no evidence of mannan crystallization in this natural occurrence. Nevertheless, cellulose microfibrils can be made to serve as a crystallization template for mannan, producing an epitaxial crystallization of the mannan chains with their fibre axes parallel to that of cellulose (3).…”

“…As in cellulose, the fiber repeat of 10.3 A corresponds to an extended disaccharide residue with a twofold screw axis relating contiguous mannosyl residues. Thanks to the high quality electron diffraction data from lamellar single crystals of mannan I, the required systematic absences of the baseplane reciprocal lattice net are unequivocal (3,7), resulting in a two-chain unit cell with anti-parallel chains, as required by the P2,2121 space group. Accordingly, a single anhydromannose residue is the asymmetric unit.…”

Microbial Mannanases: An Overview of Production and Applications

“…Unsubstituted β-1,4-mannan, composed of a main chain of β-mannopyranose residues, is an important structural component of some marine algae (Yamasaki et al, 1998) and terrestrial plants such as ivory nut (Chanzy et al, 2004) and coffee bean (Nunes et al, 2006). It resembles cellulose in the conformation of the individual polysaccharide chains, and is water insoluble.…”

Crystalline structure and packing of mannan I

“…Corrections were made for Lorentz polarization and for the arcing of the diffraction spots using the relationship F i = Ap tan 28/(1 + cos 28), where A is the cross-sectional area, 8 …”