Characterization of Betula pendula Outer Bark Regarding Cork and Phloem Components at Chemical and Structural Levels in View of Biorefinery Integration
2017
Ferreira, Joana P. A. | Quilhó, Teresa | Pereira, Helena
Betula pendula outer bark includes a cork-rich periderm and a rhytidome, including periderm and phloem layers. Cork and phloem from the outer bark were chemically analyzed after fractioning into different particle sizes; coarser fractions were obtained in higher yields. Cork and phloem chemical composition were different: the coarse and medium fractions of cork were enriched in suberin (37.7–38.4%) and lipophilic extractives (31.1%); phloem fractions were enriched in lignin (32.2%) and polysaccharides (43.0%). Lipophilic and suberin extracts were analyzed by GC-MS. Triterpenes constitute the most abundant identified compounds (90.1–97.1% in cork, 76.1–90.2% in phloem), and betulin is the most representative (64.6–70.7%). The majority of the suberin monomers are ω-hydroxyacids, (55.2–83.9%); namely, 9,10-epoxy-18-hydroxyoctadecanoic, 9,10,18-trihydroxyoctadecanoic, and 22-hydroxydocosanoic acids. A chemical valorization of the cork component from B. pendula outer bark as an industrial residue is proposed based on the fractionated production of triterpenoids, suberinic acids, oligo/monosaccharides, and lignin.
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