Degradation of dextrans

Fig. 63. Scission rate constant for the ultrasonic degradation of dextran as a function of molecular weight (M), in different solvents (according to Ref. [179]) ( ) formamide (a) 10% MgSQ4 ( ) water...

Degradation of Dextran by Ultrasonic Waves, M. Stacey, Research, 4 (1951) 48. 

Figure 8. Enzymatic degradation of dextran and carbamate derivatives of dextran by dextranase. Degree of modification (%) ...

Coimmobilization of both enzymes offers the most efficient approach for this type of reaction and its potential scale-up. Basically, action of DN on the DSR-S dextran aggregates must be considered if combined operation of both enzymes is intended. Degradation of dextran which is tightly associated with DSR-S occurs by DN and causes complete inactivation of DSR-S [27]. 

Vercauteren et al that the in vitro degradation of dextrans in the presence of lysosomal glucosidases or endodextranases is rather slow. Moreover, it was shown that chemical modification of the dextran further reduces its biodegrad-ability. ... 

The action patterns of a purified, intracellular dextranase and three intracellular a-D-glucosidases from Pseudomonas UQM733 on pure isomalto-oligosaccharides have been studied. The a-D-glucosidases had optimal activity on isomaltotetraose and were therefore classified as oligoglucanases . They have been used to determine the structure of two branched isomalto-oligosaccharides obtained by enzymic degradation of dextran. 

Portenlanger G, Heusinger H (1997) The influence of frequency on the mechanical and radical effects for the ultrasonic degradation of dextranes. Ultrason Sonochem 4 127-130... 

The opposite effect is found if dietiiyl ether is present in tlw solution. Because of its high volatflity the collapse of cavitation bubbles is considerably damped, resulting in a decrease of the rate constant. Basedow and Ebert fcxind that the rate of degradation of dextran in water was decreased to one tenth of its initiid value, if the solution was saturated with diethyl ether. 

Other important examples are blood and blood products, which are collected and processed in sterile containers, and plasma substitutes, for example dextrans and degraded gelatin. Dextrans, glucose polymers consisting essentially of (1 - 6) a-links, are produced as a result of the biochemical activities of certain bacteria of the genus Leuconostoc, e.g. L. mesenteroides (see Chapter 25). 

Fig. 5.11. Effect of irradiation time on the ultrasonic degradation of aqueous native dextran [2% w/v 60 W 30°C 20 kHz).

Fig. 5.14. The effect of the enthalpy of vaporisation on the degradation rate constant of dextran solutions. A - Water ...

Tab. 5.12a Rate constant and limiting molar masses (after 8 h ultrasonic irradiation) for the ultrasonic degradation of aqueous dextran (a) at 30°C and variable ultrasonic power (b) at an ultrasonic power input of 60 W and variable temperature.

The main product of anaerobic degradation of sugars by these organisms is lactic acid. Other products of bacterial carbohydrate metabolism include extracellular dextrans (see p. 40)—insoluble polymers of glucose that help bacteria to protect themselves from their environment. Bacteria and dextrans are components of dental plaque, which forms on inadequately cleaned teeth. When Ca salts and other minerals are deposited in plaque as well, tartar is formed. 

Cyclodextrins are formed in the degradation of starch and dextran by the action of cyclodextrin/glucanosyltran-sferases [EC 2.4.1.19]. These enzymes also catalyze so-called acceptor reactions in which the cyclodextrin ring is opened and an acceptor molecule (e.g., glucose) is added to the reducing end of the maltodextrin chain. 

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