Alginate bionanocomposite films containing sepiolite modified with polyphenols from myrtle berries extract.

Alginate nanocomposite films incorporating sepiolite (Sep) modified with myrtle berries extract (MBE) rich in polyphenols were prepared by solution casting method. The effects of different extract concentrations on the film properties were determined by measuring physicochemical, mechanical and antioxidant properties of the films. Fourier transform infrared (FTIR) spectra indicated that strong interactions between the polyphenols present in the MBE and sepiolite were involved in the films. The results suggested that incorporation of Sep-MBE hybrids into the films improved elongation at break, tensile strength, water vapor and UV barrier properties compared to the control film. The antioxidant activity of the films was significantly improved and raised with increasing content of MBE. The release kinetics results of MBE polyphenols from the active films into alcoholic food simulant indicated that the addition of Sep-MBE hybrids to alginate film is able to slow the release of MBE polyphenols. This study revealed the benefits of incorporation of Sep-MBE hybrids into the alginate films and their potential application as active packaging films or coating material.

Chemical and thermal analysis of lignin streams from Robinia pseudoacacia L. generated during organosolv and acid hydrolysis pre-treatments and subsequent enzymatic hydrolysis.

Lignin streams produced in biorefineries are commonly used to obtain energy. In order to increase the competitiveness of this industry, new lignin valorization routes are necessary, for which a depth characterization of this biological macromolecule is essential. In this context, this study analyzed lignin streams of Robinia pseudoacacia L. generated during organosolv and acid hydrolysis pre-treatments and during the subsequent enzymatic hydrolysis. These lignins included dissolved lignins from pre-treatment liquors and saccharification lignins from pre-treated materials. Chemical composition and structural features were analyzed by analytical standard methods and Fourier Transform Infrared spectroscopy (FTIR), size exclusion chromatography (SEC), 13C solid state nuclear magnetic resonance (13C NMR) and 1H-13C two-dimensional nuclear magnetic resonance (2D NMR); while thermal characterization included thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). In general, all studied lignins contained a predominance of ß-O-4' aryl ether linkages, followed by resinol (ß-ß') and phenylcoumaran (ß-5'), with a predominance of syringyl over guaiacyl and hydroxyphenyl units. Nevertheless, the dissolved lignins revealed a removal of linkages, especially ß-O-4', leading to an enrichment of phenolic groups. Moreover, high thermal stability and good thermoplasticity were characteristics of these lignins. Contrary, the saccharification lignins exhibited a more intact structure, but with an important remaining carbohydrates content.

Enhancement of enzymatic saccharification of Eucalyptus globulus: steam explosion versus steam treatment.

Steam explosion and steam pre-treatment have proved capable of enhancing enzymatic saccharification of lignocellulosic materials. However, until now, these methods had not been compared under the same operational conditions and using the same raw material. Both pre-treatments lead to increased yields in the saccharification of Eucalyptus globulus; but results have been better with steam pre-treatments, despite the more accessible surface of exploded samples. The reason for this finding could be enzymatic inhibition: steam explosion causes a more extensive extraction of hemicelluloses and releases a greater amount of degradation products which can inhibit enzymatic action. Enzymatic inhibition is also dependent on the amount and chemical structure of lignin, which was also a contributing factor to the lower enzymatic yields obtained with the most severe pre-treatment. Thus, the highest yields (46.7% glucose and 73.4% xylose yields) were obtained after two cycle of steam treatment, of 5 and 3 min, at 183°C.

Integration of a kraft pulping mill into a forest biorefinery: pre-extraction of hemicellulose by steam explosion versus steam treatment.

Growing interest in alternative and renewable energy sources has brought increasing attention to the integration of a pulp mill into a forest biorefinery, where other products could be produced in addition to pulp. To achieve this goal, hemicelluloses were extracted, either by steam explosion or by steam treatment, from Eucalyptus globulus wood prior to pulping. The effects of both pre-treatments in the subsequent kraft pulping and paper strength were evaluated. Results showed a similar degree of hemicelluloses extraction with both options (32-67% of pentosans), which increased with the severity of the conditions applied. Although both pre-treatments increased delignification during pulping, steam explosion was significantly better: 12.9 kappa number vs 22.6 for similar steam unexploded pulps and 40.7 for control pulp. Finally, similar reductions in paper strength were found regardless of the type of treatment and conditions assayed, which is attributed to the increase of curled and kinked fibers.

Lignin changes after steam explosion and laccase-mediator treatment of eucalyptus wood chips.

Eucalyptus globulus chips were steam exploded followed by treatment with a laccase-mediator system (LMS) under different experimental conditions. Removal of hemicelluloses and, to a lesser extent, lignin was observed. Thermogravimetic analyses of whole meal obtained from chips before and after steam explosion indicated an increase in lignin degradation temperature due to lignin condensation. In contrast, application of LMS treatment caused a reduction in lignin and polysaccharide degradation temperatures. Lignins were isolated from wood samples before and after each treatment and analyzed by 2D NMR and (13)C NMR. An increase in carboxyl and phenolic hydroxyl groups and a significant decrease in ß-O-4 structures were found in steam-exploded samples. The most relevant changes observed after laccase treatment were increased secondary OH and degree of condensation.