Cellobiose degradation

A summary of the key information has been compiled on the anaerobic and aerobic bacteria discussed above. Comparison of the substrates for growth of these organisms (Table I) show that all utilize cellobiose and various forms of cellulose. The two species belonging to Bacteroides have different specificity for substrates, while those for Ruminococcus, Cellulomonas and Thermomonospora were the same. Table I also allows comparison of the behavior of the 13 species of cellulolytic bacteria toward cellobiose. More variability is noted in this regard and no correlation between induction/repression can be made with the mechanism of cellobiose degradation. 

R. W. Kane and J. D. Timpa, A high-performance liquid chromatography study of D-cellobiose degradation under Fenton conditions, J. Carbohydr. Chem., 11 (1992) 779-797. 

RunUnococcus albus and Ruminococcus flavefadens. These bacteria are important cellulose-degraders found in the rumen of cattle and sheep (2). Most isolated strains ferment cellulose and xylan and all ferment cellobiose. Fermentation of glucose and some other carbohydrates depends on the particular strain. R flavefadens and B. succinogenes can ferment the highly ordered crystalline cellulosic su trates but R albus cannot. No evidence has been found for extracellular cellulase production by R albus, but Ohmiya et al. purified cellobiosidase from this culture 17). Laboratory growth of R albus has been conducted at pH 7.0 and 37 C. 

The first group is comprised that of compounds which potentially could be degraded to form G-l-P by phosphorolysis by beta-linkage specific enzymes. They include IPTGlu, cellobiose, sophorose, salicin, and sucrose. Addition of these compounds, or exogenous G-l-P, to Solka Floe fermentations improved maximum cellulase yields from 171 to 309%, and the time period for enzyme synthesis was reduced from 95 to 59% compared with using Solka Floe only. 

TGA analysis shows that polymer degradation starts at about 235°C which corresponds to the temperature of decomposition of the cellobiose monomer (m.p. 239°C with decom.). Torsion Braid analysis and differential scanning calorimetry measurements show that this polymer is very rigid and does not exhibit any transition in the range of -100 to +250 C, e.g. the polymer decomposition occurs below any transition temperature. This result is expected since both of the monomers, cellobiose and MDI, have rigid molecules and because cellobiose units of the polymer form intermolecular hydrogen bondings. Cellobiose polyurethanes based on aliphatic diisocyanates, e.g. HMDI, are expected to be more flexible. 

Subsequently, Ordin and Hall (25, 26) found that particulate preparations from oat coleoptiles could use UDP-D-glucose as substrate for polysaccharide formation. Upon degradation of the polysaccharide derived from UDP-D-glucose with impure cellulase, cellobiose, and to a lesser extent a substance identified as a trisaccharide containing mixed / -(1 - 4), / -(1 - 3) glucosyl linkages were obtained. 

Cellobiose is a sugar obtained by degradation of cellulose. If200.0 mL of aqueous solution containing 1.500 g of cellobiose at 25.0°C gives rise to an osmotic pressure of 407.2 mm Hg, what is the molecular mass of cellobiose ... 

In respect to its ability for degrading H3P04-swollen cellulose, Ci is similar to Cx, but the mode of attack clearly is different (Figure 2). Whereas Ci attacks from the end of the chain and produces little change in degree of polymerization, Cx attacks at random. Glucose, cellobiose, and cellotriose are found in the products of the action of Cx C i produces principally cellobiose, as would be expected from a cellobiohydrolase. 

Both major and minor protein components separated in this way were Ci types. This was established when it was found that either acted in synergism with a mixture of the Cx and / -glucosidase activities to the same extent in solubilizing cotton cellulose (Table II). Furthermore, both components were cellobiohydrolases in that they could degrade H3PO4 cellulose to cellobiose. 

Mannobiose was predominant throughout the enzymatic reaction its amount relative to mannose decreased, however, with incubation time (Table II). Besides mannobiose and mannose, glucose was present in the reaction solutions (Figure 2). The amount of glucose relative to the mannosaccharides increased with time it was about 1 8 after 5 hr of incubation and about 1 4-5 after 23 to 80 hr. No cellobiose and no degradation products from the arabino-4-O-methylglucuronoxylan were found (cf. Figure 2 and Table I, Columns 3 and 4). 

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