Native polysaccharides, degradation

As referred previously, two main types of cellulolytic systems are currently recognized. Those based on free , soluble enzymes, produced mostly by aerobic microbes that secrete individual cellulases, which act synergistically on native cellulose and those based on complexes of cellulolytic enzymes, or cellulosomes , produced by some anaerobic bacteria and fungi, which are usually attached to the outer surface of the microorganism [40, 101]. CBMs play a role in the phase transfer of a soluble free enzyme onto the insoluble substrate [68, 69]. CBMs are present in several polysaccharide-degrading enzymes, namely in hemicellulases [56, 58, 102], endomannanases [12], xylanases [56, 103], acetyl-xylanesterases [104] and )3-glucosidases [71]. 

The first paper on the bioactive polysaccharides from Glycyrrhiza uralensis roots was published in 1996 by Kiyohara et al. [57]. They isolated a pectic type polymer with anti-complementary and mitogenic activity that was an acidic pectin, possibly containing rhamnogalacturonan type I as part of the total structure. Degradation of the uronic acid part of the molecule decreased both types of bio activities. The neutral oligosaccharide chains were shown to retain some of the activities of the native polymer, but it was suggested that they should be attached to the acidic core to retain maximum activity. 

Although lichenin has been shown to possess an unbranched structure, further investigations, particularly of the degradation occurring during the preparation of derivatives, appear to be necessary to determine the molecular size of the polysaccharide in its native state. 

The results of the measurements of the shape and size of polysaccharides show that few such polymers have been adequately characterized. Relatively little is known of their size in the native state, and the problems concerned with the isolation of these substances, and the preparation of derivatives have not been completely solved. A paramount problem is the avoidance of degradation. Nevertheless, valuable information on the high-polymer characteristics of a number of defined polysaccharide materials has been obtained. Many polysaccharides of known chemical structure have not yet been examined, and the whole field is an attractive one for further investigations. 

As we know at present, the mucoproteose fraction includes the following materials (1) most of the gastric fucomucins, as well as some of the blood group substances, i.e., most of the neutral polysaccharides of the dissolved mucin fraction linked to their peptide moiety, (2) y-globulin and probably also P-globulin, which pass into the gastric juice from the serum (G16, G42, Hll, H20, H55) and probably account for the presence of mannose in this fraction (Gll), (3) some of the pep-tidic degradation products of serum albumin and visible mucus, which are partly dialyzable (G16, K2), (4) native intrinsic factor, the related primary vitamin Bi2 binder, and tertiary vitamin Bia binder related to the neutral mucosubstances (G14, Ul, U2). 

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