Antifungal activity in vitro using kraft-pulping crude black liquor and hydrothermal treatment black liquor against wood-decaying fungi

Abstract

We investigated antifungal properties of two kraft-pulping liquors as potential environmentally friendly wood preservatives targeting in deterioration by white rot (WRF) and brown rot fungi (BRF). The in vitro antifungal activity of crude black liquor (BL) and the product from a hydrothermal gasification (BLW_Supc) process were investigated. Both products showed high bioactivity, with BL completely inhibiting the activity of WRF and BRF; 80% was entirely suppressed at low BL concentrations (5–10% vol/vol). Using the BLW_Supc at 2.55% wt/wt, we achieved the same inhibitory effect as BL (15% vol/vol) for the two fungi. These antifungal effects can be explained by the composition of liquors that act as antioxidants, promoting enzymatic inactivation and inhibiting the growth of WRF and BRF. BLW_Supc exhibited radical quenching activity against DPPH of 43.9%, and the BL, a phenolic content about 20 times higher (23.635 mg/L) than BLW_Supc (2.093 mg/L), suggesting that antifungal activity of BL and BLW is related to their chemical composition. An opportunity demonstrated by this study is the reuse of BLW_Supc as a protective treatment within a sustainable chain.

Keywords:

• Brown rot
• wood protection
• white rot
• phenolics compounds
• lignin kraft pulping

Conflict of interest

We declare that we have no conflict of interest.

Additional information

Funding

The authors are grateful for the assistance provided by the Research Support Centers Complex (COMCAP/UEM) of the State University of Maringa and the Biodeterioration and Wood Protection Laboratory at the Federal University of Espírito Santo (UFES) for the provision of fungal strains. This study was financed by the Coordination for the Improvement of Higher Education Personnel - Brazil (CAPES) - Finance Code 001.