| Autor: |
Ibarra D; Forest Sciences Institute (ICIFOR-INIA), CSIC, Ctra. de la Coruña Km 7.5, 28040 Madrid, Spain., García-Fuentevilla L; Forest Sciences Institute (ICIFOR-INIA), CSIC, Ctra. de la Coruña Km 7.5, 28040 Madrid, Spain., Domínguez G; Department of Biomedicine and Biotechnology, University of Alcalá, 28805 Alcalá de Henares, Spain., Martín-Sampedro R; Forest Sciences Institute (ICIFOR-INIA), CSIC, Ctra. de la Coruña Km 7.5, 28040 Madrid, Spain., Hernández M; Department of Biomedicine and Biotechnology, University of Alcalá, 28805 Alcalá de Henares, Spain., Arias ME; Department of Biomedicine and Biotechnology, University of Alcalá, 28805 Alcalá de Henares, Spain., Santos JI; General Services of Research SGIKER, University of the Basque Country (UPV/EHU), Edificio Joxe Mari Korta Avda. Tolosa 72, 20018 Donostia-San Sebastian, Spain., Eugenio ME; Forest Sciences Institute (ICIFOR-INIA), CSIC, Ctra. de la Coruña Km 7.5, 28040 Madrid, Spain. |
| Abstrakt: |
The usage of laccases is a sustainable and environmentally friendly approach to modifying the Kraft lignin structure for use in certain applications. However, the inherent structure of Kraft lignin, as well as that resulting from laccase modification, still presents challenges for fundamental comprehension and successful lignin valorization. In this study, bacterial and fungal laccases were employed to modify eucalypt Kraft lignin. To evaluate the type and range of the chemical and structural changes of laccase-treated lignins, different NMR techniques, including solution 1 H and 2D NMR (heteronuclear single quantum correlation (HSQC)), and solid-state 13 C NMR, were applied. Size exclusion chromatography and infrared spectroscopy were also used. Interestingly, HSQC analysis showed substantial changes in the oxygenated aliphatic region of lignins, showing an almost complete absence of signals corresponding to side-chains due to laccase depolymerization. Simultaneously, a significant loss of aromatic signals was observed by HSQC and 1 H NMR, which was attributed to a deprotonation of the lignin benzenic rings due to polymerization/condensation by laccase reactions. Then, condensed structures, such as α-5', 5-5', and 4-O-5', were detected by HSQC and 13 C NMR, supporting the increment in molecular weight, as well as the phenolic content reduction determined in lignins. |
