Native polysaccharides, degradation enzymic

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]. 

Because of the lack of homogeneous, purified, cellulose-degrading enzymes, having a variety of action patterns, that will act on the native, unmodified polysaccharide, it has not yet been possible to investigate the fine structure of cellulose in a manner analogous to that used for amylose. The situation is complicated by the insolubility of the substrate and its resistance to degradation by any single enzyme. A system of enzymes, the function of at least one component of which is at present unclear, is required. For this reason, it has not yet been possible to examine the fine structure of cellulose enzymically. 

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