D-Linked Glucans

All reports on starchlike polymers cannot be covered herein. However, the cell walls of Fusicoccum amygdali are stained blue with iodine and attacked by alpha amylase.8 Extracts of Sporothrix schenckii 

Many other fungi contain alkali-soluble, (1— 3)-linked a-D-gluco-pyranans these are summarized in Table I. In Histoplasma capsula-tum, the cell wall contains a glucan, whereas the mycelial form con- 

Fungi Whose Cell Walls Contain Alkali-Soluble, (1— 3)-Linked a-D-Clucopyranans 

Few reports exist on nigeran, except that it occupies an inaccessible position in the cell wall of Aspergillus niger, and is resistant to enzymic attack.32 

An a-D-glucopyranan from fruit bodies of Lentinus edodes is slightly branched, with (1— 3) and (1— 4) linkages in the ratio of 5.3 1. It is partially degraded by amylolytic enzymes, and it was concluded that the (1— 4) linkages are concentrated in regions not far from nonreducing ends.33 

Kooiman separated exocellular amylose formed in liquid media at pH 5 by Cryptococcus albidus and Cryptococcus laurentii var. flavescens NRRL Y-1401 from a polysaccharide containing D-man-nose, D-xylose, and D-glucuronic acid. X-Ray diffraction patterns of the retrograded amyloses were identical with that of tuber starch (B modification). Periodate oxidation, optical rotational measurements, and hypoiodite oxidation data suggested a linear a-D-(l— 4)-linked structure having a chain length of about 44 units for the Cr. albidus amylose. Cryptococcus neoformans produces a crystalline amylose that was isolated by the method of Schoch. It has an iodine value and alpha- and hefa-amylase hydrolysis characteristics similar to those of corn amylose. 

Early comparisons of glycogens of bakers yeast and of animal origin were made on the basis of the red-brown color formed with iodine solution, the specific rotation, and the opalescent appear-ance. Jeanloz, in 1944, purified yeast glycogen by electrodialysis, 

Aspergillus oryzae A glycogen-like material occurs in the sorocarps of Dictyostelium discoideum. It is attacked by alpha-amylase or by a mixture of alpha- and befc-amylase, and, althou inert to beta-amylase, it becomes susceptible after treatment with hot, aqueous alkali.  

Property Bakers yeast Brewers yeast Babbit liver Polyporus gigantetis  

Data on pullulan gathered by Wallenfels, Lindberg, and Adams and their coworkers are consistent with a linear polymer containing mainly maltotriose residues connected by a-D- l- 6)-linkages (1). Pullulan prepared directly from solution or through 

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Figure 2 compares the conformational transition curves of wild-type yeast glucan (branch frequency = 0.20) and PGG (branch frequency = 0.50). Wild-type yeast glucan required approximately 0.1M NaOH to disrupt the triple helical conformation, whereas this transition is observed at approximately 0.04 M NaOH with PGG. This trend is consistent with the observation that curdlan, an entirely linear p-D(l-3)-linked glucan, requires approximately 0.25M NaOH to disrupt the ordered conformation (76). Hence, it is concluded that the highly branched PGG molecules only form weak inter-chain associations resulting in the formation of predominantly single-helical zones. 

On the basis of the data, it was concluded1 that the synthetic polyglucoses obtained by this method are linear, /3-d- (1— 4) -linked glucans which possess properties similar to those of cellulose. It is especially significant that this polymerization proceeded with apparent stereospecificity, to form only the /S-d anomeric linkage. The mild conditions under which the polycondensation occurs probably contribute to this selectivity of reaction. 

In an effort to prepare a stereospecifically (1—>6)-linked glucan, the polymerizatioii of l,6-anhydro-2,3,4-tri-O-benzyl-0-D-glucopyranose (tri-O-benzylievoglucosan) has been studied. Polymerization of this monomer in dichloromethane at —78°, using the Lewis acid catalyst, phosphorus... 

Kim YT, Kim EH, Cheong C, Williams DL, Kim CW, Lim ST (2000) Structural characterization of beta-D-(l fwdarw 3, 1 fwdarw 6)-linked glucans using NMR spectroscopy. Carbohydr Res 328 331-341 Kirchman DL (2002) The ecology of Cytophaga-Flavo-bacteria inaquatic environments. FEMS Microbiol Ecol 39 91-100... 

The cell wall of Saccharomyces cerevisiae has a structure of crossed molecules of /3-D-linked D-glucan, which gives the wall its strength and the cell its shape. This glucan is embedded in other polysaccharide(s) or in glycoprotein. Thus, yeast cell-walls consist mainly of polysaccharide, with relatively little protein, lipid, or min-... 

Pullulan is a glucan of (1 6)-a-D-linked maltotriose residues produced by Aureobasidium pullulans from starch or sucrose feedstockJ It is well soluble in aqueous medium and forms films that possess thermal stability and are antistatic and elastic. Pullulan has adhesive properties and is directly compressible under heat with moisture. The polysaccharide is produced on an industrial scale and is used for multiple applications, including food, pharmaceuticals, and cosmetics. It has recently been classified as GRAS by the U.S. FDA. 

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