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Levulinic acid: a novel sustainable solvent for lignin dissolution

Publication . Melro, Elodie; Filipe, Alexandra; Valente, Artur J. M.; Antunes, Filipe E.; Romano, Anabela; Norgren, Magnus; Medronho, Bruno

Lignin is a natural, renewable resource with potential to be used in biomaterials. Due to its complex structure, its efficient dissolution is still challenging, which hinders its applicability at large scale. This challenge become harder considering the current need of sustainable and environmentally friendly solvents. To the best of our knowledge, this work reports for the first time the dissolution of kraft lignin in levulinic acid, a "green" solvent, and compares its efficiency with common carboxylic acids and sulfuric acid. It has been found that levulinic acid has a high capacity to dissolve kraft lignin at room temperature (40 wt% solubility), and it efficiency is not compromised when diluting the acid with water (up to 40 wt% water content). the Kamlet-Taft pi* parameter of the different acidic solvents was estimated and found to correlate well with their solubility performance. Lignins previously dissolved in levulinic and formic acids were selected to be regenerated and minor differences were found in thermal stability and morphological structure, when compared to native kraft lignin. However, an increase in the content of the carbonyl groups in the regenerated lignin material was observed. (C) 2020 Elsevier B.V. All rights reserved.

2020-12Journal article

Open access

Encapsulation of Rosmarinus officinalis essential oil in β‐cyclodextrins

Publication . El Kharraf, Sara; Farah, Abdellah; El Hadrami, El Mestafa; El‐Guendouz, Soukaïna; Lourenço, João P.; Rosa Da Costa, Ana; Miguel, Maria

The aim of this study was to investigate the encapsulation process of R. officinalis (rosemary) essential oil (REO) in beta cyclodextrin (beta-CD), by co-precipitation, using response surface methodology (RSM), specifically the face-centered central composite design (FCCCD). Solid-to-solid (beta-CD/REO) and liquid-to-liquid (ethanol/water) ratios were selected as independent variables and their influence on the dependent variables was assessed. The recovered powder was characterized by different techniques, such as scanning electron microscope (SEM), Fourier Transform-Infrared Spectroscopy (FTIR) and X-Ray Diffractometry (XRD). Moreover, the release of REO from the beta-CD complexes was investigated at different temperatures and pH values. The responses were affected by the concentration of ethanol in the reaction mixture and the amount of REO used. The optimal responses set by the RSM model (p-value < 0.05) were obtained for the optimal parameters ranging from 1.25:1 to 1.7:1 and 16.25:83.75 to 17.5:82.5 for ethanol/water and beta-CD/REO ratios, respectively. The size of the inclusion complexes from the experimental condition 1:1 ethanol/water and 10:90 beta-CD/REO ratios was the highest, with a value of 2.735 +/- 0.192 mu m. Furthermore, the FTIR spectra of inclusion complexes revealed a band downshift relative to the spectrum of beta-CD, attributable to hydrogen bonding between REO components and beta-CD, as well as a new band at 1,747 cm(-1), revealing the presence of oil components, while the XRD patterns of beta-CD recorded before and after the inclusion process indicate a change from a cage-type packing to a channel-type packing of cyclodextrin, which, in turn, indicates a successful inclusion process. Practical applications The encapsulation of EOs into cyclodextrins can enhance their biological properties, which include antioxidant, antimicrobial, anticarcinogenic, anti-inflammatory, and antidepressant activities. Nevertheless, a careful evaluation of the encapsulation conditions should be carried out in order to ensure the highest encapsulation yield without quality loss. In this way, pH and temperature, among other conditions, must be considered for evaluation since food or other matrices may present diverse pH values and be subjected to different temperatures. The present work may contribute to the use of rosemary EOs, with antioxidant and antimicrobial properties, in food and cosmetic industries, avoiding the sometimes-unpleasant flavor and aroma characteristics.

2021Journal article

Restricted access