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Bark biorefinery: deconstruction and chemical potential of Eucalyptus globulus and Picea abies barks
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Resumo(s)
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
Descrição
Doutoramento em Engenharia Florestal e dos Recursos Naturais / Instituto Superior de Agronomia. Universidade de Lisboa
Palavras-chave
bark fractionation enzymatic hydrolisis lignin characterization extractives bioactivity Kraft pulp
Contexto Educativo
Citação
Neiva, D.M. - Bark biorefinery: deconstruction and chemical potential of Eucalyptus globulus and Picea abies barks. Lisboa: ISA, 2020, 196 p.