SUSFOR PROGRAM: SUSTAINABLE FORESTS AND PRODUCTS

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Hydroxystilbene glucosides are incorporated into Norway spruce bark lignin

Publication . Rencoret, Jorge; Neiva, Duarte M.; Marques, Gisela; Gutiérrez, Ana; Kim, Hoon; Gominho, Jorge; Pereira, H.; Ralph, John; Rio, José C. del

Recent investigations have revealed that, in addition to monolignols, some phenolic compounds derived from the flavonoid and hydroxystilbene biosynthetic pathways can also function as true lignin monomers in some plants. In this study, we found that the hydroxystilbene glucosides isorhapontin (isorhapontigenin-O-glucoside) and, at lower levels, astringin (piceatannol- O-glucoside) and piceid (resveratrol-O-glucoside) are incorporated into the lignin polymer in Norway spruce (Picea abies) bark. The corresponding aglycones isorhapontigenin, piceatannol, and resveratrol, along with glucose, were released by derivatization followed by reductive cleavage, a chemical degradative method that cleaves b-ether bonds in lignin, indicating that the hydroxystilbene glucosides are (partially) incorporated into the lignin structure through b-ether bonds. Twodimensional NMR analysis confirmed the occurrence of hydroxystilbene glucosides in this lignin, and provided additional information regarding their modes of incorporation into the polymer. The hydroxystilbene glucosides, particularly isorhapontin and astringin, can therefore be considered genuine lignin monomers that participate in coupling and crosscoupling reactions during lignification in Norway spruce bark

2019Journal article

Open access

An integrated characterization of Picea abies industrial bark regarding chemical composition, thermal properties and polar extracts activity

Publication . Neiva, Duarte M.; Araújo, Solange; Gominho, Jorge; Carneiro, Angélica de Cássia; Pereira, Helena

The present work determines the chemical and thermal characteristics as well as the phytochemical and antioxidant potential of the polar extractives of the Picea abies bark from an industrial mill, their wood and bark components and also different bark fractions obtained by mechanical fractionation (fine B1, Φ<0.180 mm, medium B3, 0.450 < Φ<0.850 mm and coarse B6, 2 < Φ<10 mm). The aim is to increase the knowledge on the Picea abies bark to better determine possible uses other than burning for energy production and to test an initial size reduction process to achieve fractions with different characteristics. Compared to wood, bark presented similar lignin (27%), higher mineral (3.9% vs 0.4%) and extractives (20.3% vs 3.8%) and lower polysaccharides (48% vs 71%) contents. Regarding bark fractions the fines showed higher ash (6.3%), extractives (25%) and lignin (29%) than the coarse fraction (3.9%, 19% and 25% respectively). Polysaccharide contents increased with particle size of the bark fractions (38% vs 52% for B1 and B6) but showed the same relative composition. The phytochemical profile of ethanol and water extracts presented higher contents for bark than wood of total phenols (2x higher), flavonoids (3x higher) and tannins (4- 10x higher) with an increasing tendency with particle size. Bark antioxidant activity was higher than that of wood for ferric-reducing antioxidant power (FRAP, 10 vs 6 mmolFe2+/gExt for the ethanol extract) and free radical scavenging activity (DPPH, 6 vs 18 mg/L IC50 for the ethanol extract) methods. The different bark fractions antioxidant activity was very similar. Bark thermal properties showed a much lower volatiles to fixed carbon ratio (V/FC) than wood (3.1 vs 5.2) although the same higher heating value (20.3 MJ/kg). The fractions were quite similar. Bark presented chemical features that point to their possible upgrade, whether by taking advantage of the high extractives with bioactive compounds or the production potential for hemicellulose-derived oligomers with possible use in nutraceutical and pharmaceutical industries

2018Journal article

Open access

Bark biorefinery: deconstruction and chemical potential of Eucalyptus globulus and Picea abies barks

Publication . Neiva, Duarte Miranda; Pereira, Helena; Gominho, Jorge

Eucalyptus globulus and Picea abies barks are huge industrial residues with upgradable potential. This research thesis aims at further the knowledge on these barks envisaging production of biomaterials, building blocks, chemicals and fuels. Both industrial barks contained high wood and mineral extraneous contaminants, presenting higher extractives (10-20%) and ash (4-5%), but lower polysaccharides (52-61%) than their respective woods. E. globulus bark hemicelluloses (glucuronoxylan) and lignin (S/G=2.8, enriched in β-O-4’, 83% of all inter-unit linkages elucidated by 2D HSQC-NMR) were similar to those of wood, while P. abies bark differed substantially in hemicelluloses (pectin, higher arabinan, lower mannan) and lignin (γ-OH significant acetylation, presence of hydroxystilbenes glucosides as “nonconventional” true lignin monomers, adding to the canonical established monolignols precursors). The presence of glucosides in lignin was reported for the first time with positive ramifications regarding possible design and bioengineering of polymers with special attributes (hydrophilicity, bioactivity) Deconstruction pathways were tested considering the knowledge gathered. Bleached kraft pulp was produced from E. globulus bark due to previously determined appropriate physical and chemical characteristics. Hydrothermal pre-treatment tested decreased extractives content allowing for lower active alkali (15%) usage in pulping process (resulting in 40% yield) with subsequent bleached pulp and respective handsheets showing similar characteristics to those produced with E. globulus wood. Bark proved to be a possible fiber source feedstock for pulp and paper production. Crude extracts recovered with different solvents were analyzed for neutral monosaccharides and phenolic composition, antioxidant activity, antimicrobial and quorum-sensing potential. Polar extracts showed good or very good antioxidant activity. Gram positive and Candida strains had their growth highly impaired when exposed to n-hexane and ethanol extracts concentrations above 0.04 mg/mL. Extractive-free barks were autohydrolysed and the solid residues saccharified with commercial enzymes (Saczyme and Ultimase), resulting in xylooligosaccharides/arabinooligosaccharides enriched liquors from autohydrolysis, glucose rich streams from enzymatic saccharification and lignin enriched solid residues. This thesis evidences that these abundant industrial residues are interesting materials to be upgraded within a biorefinery concept of full biomass utilization with potential to generate several products and streams with different end-uses

2020Doctoral thesis

Open access