Alkaline extraction of polyphenols for valorization of industrial spruce bark

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7 Citations (Scopus)


Industrial spruce bark is an abundant side-stream from forest industries that contains tannins and other phenolic compounds that can be exploited in a variety of applications. In this study, alkaline extractions of spruce bark conducted under a wide range of process conditions showed that 20–27 % of the bark could be extracted as polyphenols, mainly tannins and some lignin. The polyphenols in alkaline extracts from two selected scale-up extractions, conducted at 100 °C with 15 % NaOH and at 160 °C with 24 % NaOH, were then recovered by acidic precipitation and tested as surfactants. Despite their different composition, the polyphenol-rich precipitates showed similar surface activity than a commercial biosurfactant, and were also soluble under neutral conditions. Moreover, sugar yields above 80 % could be obtained by enzymatic saccharification of the extracted bark residues. These results demonstrated that alkaline extraction is a promising technology for valorization of industrial bark side-streams.

Original languageEnglish
Article number101129
Number of pages8
JournalBioresource Technology Reports
Early online date23 Jun 2022
Publication statusPublished - Sept 2022
MoE publication typeA1 Journal article-refereed


  • Alkaline extraction
  • Bark
  • Polyphenols
  • Saccharification
  • Surface tension
  • Tannins


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