Enzymatic and chemical degradation of curdlan targeting the production of β-(1 → 3) oligoglucans

Obtaining biologically active oligosaccharides from hydrolysed polysaccharides is nowadays of great interest. Curdlan is one of the polysaccharides with interesting properties and represents the main source for β-(1 → 3)-oligoglucans. Curdlan degradation remains a challenge due to its high resistance to hydrolysis. In this study, curdlan was hydrolysed both with mild acid treatments (TFA or H2SO4, 1 M) as well as with the use of an unpurified enzymic extract produced from Trichoderma harzianum. The kinetics of degradation and the production of the β-(1 → 3)-oligoglucans were followed in detail by HPAEC analysis. A comparison of results clearly demonstrated the advantage of the enzymic extract with a complete hydrolysis of the curdlan within 90 h whereas less than 25% hydrolysis yield can be reach with the acidic methodologies. More, the quality of the obtained compounds is particularly dissimilar even between the two acid treatments

Flax ( Linum usitatissimum ) Seed Cake: A Potential Source of High Molecular Weight Arabinoxylans?

International audienceWater-soluble polysaccharides were extracted from flaxseed cake and analyzed. Two groups were separated by anion-exchange chromatography. The first one (nonretained) was the major fraction (83%) and possessed a high molecular weight (HMW) arabinoxylan (56%) with an Ara/Xyl ratio of 0.32 and an Mw of 846 000. This polymer was accompanied by a smaller galactoglucan (44%), with an Mw of 6.5 × 104. The latter group (17%), retained by the gel, was further described as a HMW pectin heterogeneous group, with, respectively, 3.1 × 105 and 1.3 × 105. Despite the presence of HMW arabinoxylans, the investigation of rheological flow sweep at the concentration of 2% (w/v) has shown a slight shear thinning behavior with a small zero-rate viscosity at 9.6 Pa·s

Contributions of Intermolecular Interactions between Constitutive Arabinoxylans to the Flaxseeds Mucilage Properties

International audienceThe main fraction (about 75%) of the mucilage extracted from seeds of Linum usitatissimum which consists of arabino-xylans (AX) has been studied in dilute and semidilute regimes by SEC/MALLS analysis and rheology, respectively. It has been found that AX contains 3 populations of about 5 000 000 g mol-1 (less than 10%), 1 000 000 g mol-1 (about 40%), and 200 000 g mol-1 (about 50%). We have also observed a great retention of polymer during the filtration procedure, which is much pronounced as the AX concentration increases. This evidences the presence of large aggregates in the solution. The retention can be greatly diminished if the filtration is conducted under higher temperature. Aggregation could result from the establishment of intermolecular associations via hydrogen bonds. This hypothesis seems to be confirmed by the two higher populations in molar masses which present a random coil conformation consistent with a low degree of branching. Rheological measurements, conducted at 20 g L-1, have confirmed the association tendency leading to pseudo gels behavior. Viscoelastic properties have been evidenced by time−temperature master curves of dynamic spectra. Such master curves have also been established with addition of chaotropic (i.e., KSCN) and lyotropic (i.e., NaCl) salts. It has been shown that intermolecular associations are greatly diminished under chaotropic salts influence. This has been also confirmed by SEC/MALLS analysis. These results point out the role of hydrogen bonds in the organization of the AX system

History of mediaeval political theory in the west /

v.1. Second century to the ninth, by A.J. Carlyle. - v.2. Political theory of the Roman lawyers and the canonists, from the tenth century to the thirteenth century, by A.J. Carlyle. - v.3. Political theory from the tenth century to the thirteenth, by A.J. Carlyle. - v.4. Theories of the relation of the empire and the papacy from the tenth century to the twelfth, by A.J. Carlyle. - v.5. Political theory of the thirteenth century, by R.W. Carlyle and A.J. Carlyle. - v.6. Political theory from 1300 to 1600, by A.J. Carlyle.Mode of access: Internet