Enzymatically prepared n-alkyl esters of glucuronic acid: the effect of freeze-drying conditions and hydrophobic chain length on thermal behavior.

In this work, some of the physicochemical properties of enzymatically prepared n-alkyl esters of glucuronic acid are presented. Two questions are addressed. The first concerns the influence of post-purification freeze-drying conditions on octyl glucuronate thermotropic behavior. Depending on the amount of water added before freeze-drying, the alpha/beta anomeric ratio determined by (1)H NMR is affected and differences are observed in DSC thermograms probably due to polymorphism. The second question concerns the effect of hydrophobic chain length on the thermal behavior. An increase of both transition temperature and transition enthalpy is observed by increasing the number of carbon atoms in the alkyl chain (C8

Influence of homogenization treatment on physicochemical properties and enzymatic hydrolysis rate of pure cellulose fibers.

The aim of this study is to compare the effect of different homogenization treatments on the physicochemical properties and the hydrolysis rate of a pure bleached cellulose. Results obtained show that homogenization treatments improve the enzymatic hydrolysis rate of the cellulose fibers by 25 to 100 %, depending of the homogenization treatment applied. Characterization of the samples showed also that homogenization had an impact on some physicochemical properties of the cellulose. For moderate treatment intensities (pressure below 500 b and degree of homogenization below 25), an increase of water retention values (WRV) that correlated to the increase of the hydrolysis rate was highlighted. Result also showed that the overall crystallinity of the cellulose properties appeared not to be impacted by the homogenization treatment. For higher treatment intensities, homogenized cellulose samples developed a stable tridimentional network that contributes to decrease cellulase mobility and slowdown the hydrolysis process.

Influence of steam explosion on physicochemical properties and hydrolysis rate of pure cellulose fibers.

The aim of this study is to compare the effect of different steam explosion treatments on the physicochemical properties and the hydrolysis rate of a pure bleached cellulose. The results showed that moderate steam explosion treatments (severity factor below 5.2) did not appear to improve the enzymatic hydrolysis rate of the cellulose fibers. However, characterization of the samples showed a modification of the physicochemical properties of the cellulose, resulting in an increase of the water retention values (WRV) coupled to an increase of the overall crystallinity. For higher treatment intensities, an important thermal degradation of the cellulose was highlighted. This thermal degradation caused an important modification of the cellulose composition which leads to a decrease of the hydrolysis rate.