Condensed tannins from pine bark: A novel wood surface modifier assisted by laccase

• Published in: Industrial crops and products 2017-09, Vol.103, p.185-194
• Main Authors: Filgueira, D., Moldes, D., Fuentealba, C., García, D.E.
• Format: Article
• Language: English
• Subjects: Condensed tannins; Grafting; Hydroxypropylation; Laccase; Pinus radiata
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2017.03.040

[Display omitted] •Polyflavonoids from Pinus radiata bark is proposed as a wood surface modifier.•The pH, laccase enzyme, and the chemical modification of polyflavonoids affect the grafting on the wood surface.•Grafting of modified/unmodified polyflavonoids onto the wood surface was enhanced by using laccase at pH 10. Condensed tannins (CTs) from Pinus radiata bark were chemically modified with propylene oxide in order to improve their hydrophobicity for beech wood (Fagus sylvatica L.) surface modification. CTs and hydroxypropylated tannins (HPTs) were used for laccase catalyzed wood surface grafting at different pH (3, 7, and 10) for the first time. The impact of the modification on the wood surfaces was evaluated by FT-IR mapping, Confocal Fluorescence Emission Microscopy (CFEM) and Water Uptake Behavior (WUB). The effect of the enzyme was evaluated by measuring the total phenolic content (TPC) of the washing solution. The leaching of CTs and HPTs was decreased due to the enzyme activity. HPTs showed up to 30% less leaching after the surface coating in comparison to CTs. CFEM results suggested that the best grafting conditions occurred at pH 10, for both polyphenols used. CT- and HPT-treated samples increased their surface hydrophobicity, which resulted in a lower water uptake, during the first 12h. The results highlighted that the enzymatic grafting of CTs and HPTs on beech wood surfaces can be a promising strategy for the functionalization of lignocellulosic materials in order to provide new properties for a wide range of applications.