Purification, polysaccharides

However, in comparing results among different sample preparations many factors, such as the time of harvesting the polysaccharide, purification techniques, and preparative fractionation, will result in samples of slightly different characteristics. In one preparation, we could not even dissolve the group C polysaccharide in buffer solution before further treatment. Thus, we are not surprised to find the molecular weight difference between C-1 and C(ll) polysaccharides as listed in Table I. 

The author thanks Universidad Nacional de San Luis [Project 2-81/11], FONCyT [PICT 2004-N°23-2548 and PICT 2008-N 21-84], CONICET [PIP 6324 Res. 1905/05] and PROIPRO 2-2414 [Regional Polysaccharides Purification and Physicochemical Characterization. Applications Analytics, Separative Processes and Food Industry] for the financial support. 

R673 E. K. Fukuda, A. F. D. Vasconcelos, A. C. Matias, A. De Melo Barbosa, R. F. H. Dekker and M. L. Corradi da Silva, Fungal Cell Wall Polysaccharides Purification and Characterization , Semina Ciencias Agrarias,... 

Ultrafiltration can be introduced in the polysaccharide purification scheme instead of the alcohol precipitation step, but the membranes must be optimized in each case. Fouling of the membrane can completely change its selectivity, and the fouling properties of the solution depend on the way the extract is obtained. Twin-screw extrusion or stirred extraction leads to solutions with partially hydrolyzed molecules. The size spectra of the molecules is very large, and the small molecules produced can be a source of membrane fouling. The best performance is obtained with the 50 kDa membrane for the stirred extract and with the 10 kDa, as concerns the twin-screw extract. It can be concluded from these results that the twin-screw extract contains smaller molecules than the stirred extract. 

This seaweed became known as Irish moss. The extraction and purification of the polysaccharide from Irish moss was patented in 1871 (29). This polysaccharide eventually became known as carrageenan it was not produced and marketed until 1937. 

Purifications are made simpler with Toyopearl HW media because there is no risk of leached polysaccharides to contaminating eluted fractions. Saccharide derivatives have been known to leach from conventional low-pressure column packings, such as dextran or agarose gels. 

In 1967, Heidelberger, Stacey et al. reported the purification, some structural features, and the chemical modification of the capsular polysaccharide from Pneumococcus Type I. Difficulties of direct hydrolysis of the polysaccharide were overcome and it was possible to identify some of the fragments in the hy-drolyzate. At least six products resulted from nitrous acid deamination. Two were disaccharides, which were identified, and sequences of linked sugar units were proposed. As modification of the polysaccharide decreased the amounts of antibody precipitated by anti-pneumococcal Type I sera, the importance of the unmodified structural features in contributing to the specificity of the polysaccharide was indicated. 

This class of polysaccharide was well known in sugar refineries as the causative agent of ropiness it was formed from cane or beet sugar by bacteria of the Leuconostoc genus. Over many years, numerous papers were published, mainly with E. J. Bourne [Adv. Carbohydr. Chem. Biochem., 34 (1977) 1-22] and S. A. Barker as co-authors, describing the isolation, purification, properties, and structural features of dextrans. 

The isolation and purification of sufficient amoimts of pure bioactive polysaccharides in a reproducible manner was difficult due to the lack of isolation and purification methods. 

In a more recent study it was shown that the roots from G. uralensis, after isolation, fractionation and purification, contain two bioactive polysaccharides of the pectin family termed GU-3IIa-2 and 3IIb-l. 

Fractionation. The process by which components are extracted firm bacterial eells or from the medium in whieh the baeteria are grown and obtained in a purified form. The polysaccharide antigens of Neisseria meningitidis are separated from the bacterial cells by treatment with hexadecyltrimethylammonium bromide and those of Streptococcus pneumoniae with ethanol. The purity of an extracted material may be improved by resolubilization in a suitable solvent and precipitation. After purification, a component may be dried to a powder, stored indefinitely and, as required, incorporated into a vaccine in precisely weighed amounts at the blending stage. 

Neisseria meningitidis Types A and Ct, Cultures of N. meningitidis of serotypes A and C 1 Precipitation with hexadecyl-trimethyammonium bromide 2 Solubilization and purification 3 Blending 4 Freeze-drying Estimation of capsular polysaccharide content ... 

Total polysaccharides were recovered in the ultrafiltration retentates on a Carbosep M5 membrane (Tech-Sep, MWCO 20 kDa) in the case of the red wine, or on a Centricon 30 membrane (Amicon, MWCO 30 kDa) in the ease of the apple and tomato juices. RG-II purification from the total polysaccharide coneentrates included, if necessary, several chromatography steps ... 

Polysaccharide formation may be endocellular, exocellular or capsular. The polysaccharide is usually a normal metabolic product, frequently a major product. Isolation and purification of a bacterial polysaccharide generally involve continued precipitations from a buffered solution, together with electrodialysis or ultrafiltration. 

A large number of polyfructosans that have been reported from time to time by different authors have been investigated by Schlubach and his associates. In order to obtain polysaccharides of constant optical rotation, 100 to 300 precipitations from aqueous solution by the addition of alcohol were necessary. Fifty to 150 precipitations from chloroform solution with petroleum ether were required for purification of the acetate derivatives. These were methylated according to the procedure of Haworth and Straight,24 and upon hydrolysis partially methylated fructoses were obtained. 

The polysaccharide was acetylated with acetic anhydride in the presence of pyridine. Purification of the acetate consisted in precipitation of a 10% boiling benzene solution with petroleum ether. One hundred and fifty such precipitations were necessary before a constant-rotating product resulted [a]D20 = — 20.1° (c = 1.0, chloroform). Cryoscopic molecular weight determinations in benzene solution gave an average value of 3918. 

D-aZbacterial polysaccharides.174- 176(al Plants show heptulokinase activity176 1 the purification of D-aZfro-heptulose phosphate from Sedum spectabile has been described.176 1 The occurrence of D-wumno-heptulose phosphate in... 

The purification of a pneumococcal polysaccharide may be difficult, and the polysaccharide material is sometimes contaminated by a cell-wall component known as the C-substance. The methods for structural analysis of polysaccharides (which, like several of the pneumococcal polysaccharides, contain amino sugar and uronic acid... 

Microbial polysaccharides, 20 573-578 major, 20 574t purification of, 20 574-575 Microbial reductions, 76 401-402 Microbial resistance, origin and spread of, 75 303-304... 

The ubiquity of lignin in plant tissue presents an obstacle to the removal and purification of xylan. Lignin retards or prevents the complete solution of xylan either because of mechanical obstruction or perhaps by reason of attachment through as yet unidentified covalent bonds. Furthermore, lignin is partially soluble in the various aqueous alkaline solutions used for dissolving xylan and, consequently, poses a purification problem in various subsequent steps designed to isolate the pure polysaccharide. 

Many substances besides xylan may be extracted from plant material and, hence, if this polysaccharide alone is desired one or preferably more purification steps must be employed. 

---