Abstract

The continuous increasing in phenol price has lead to the search for new sources of raw material for formulation of adhesive resins for wood panels. The aim is to replace completely or partially the phenol from a nonrenewable to a renewable source. Lignin is one of the most abundant polymers in nature, composed by phenolic structures which could be a technically and sustainable alternative. Wood decomposition caused by brown rot fungi could allow the obtainment of a biomodified lignin (biolignin or BLG) with suitable chemical characteristics to replace phenol in the preparation of adhesive resins. In order to obtain the biolignin in an economically feasible way, and considering that in nature the biodegradation of wood by brown rot fungi takes a long time, the requirement is to decrease the time needed to it from years to a few weeks. In this study, Pinus radiata wood chips were decayed by the brown-rot basidiomycete Gloeophyllum trabeum using soil (GPS) and compost (GPC) as support in order to evaluate their effect on the biodegradation rate compared to a control without support (GP). Mass loss and chemical characterization (soluble and insoluble lignin determination) of wood chips inoculated under laboratory conditions were determined at 30, 60, 90 and 120 days of biodegradation. In parallel, the chemical characterization of a naturally biodegraded P. radiata (natural biolignin) was performed. Samples collected at 90 and 120 days from the inoculated wood chips, and natural biodegraded wood were extracted with alkali to obtain a soluble fraction of biolignin. The reactivity of the biolignin with formaldehyde through hydroxymethylation was evaluated. Results showed that mass loss of wood was higher when using soil as support for biodegradation, reaching 36% loss after 120 days. The maximum lignin content in wood chips decayed under laboratory conditions, was obtained using compost as support (48 %), which was significantly lower than the naturally degraded wood, which had a low proportion of carbohydrates (<10%) and high lignin content (~ 82%). The reactivity of laboratory and natural biolignin with formaldehyde was similar and consistent to those published earlier. The next step of the investigation is to assess the replacement of phenol currently used in the formulation of adhesive resins (especially in the plywood industry) by biolignin.