Microbial dyes: dyeing of poplar veneer with melanin secreted by Lasiodiplodia theobromae isolated from wood.

Dyeing methods that conform to environmental protection requirements and adapt to the development of industry are investigated using bleached poplar wood dyed with melanin secreted by Lasiodiplodia theobromae in this paper. Prolonging the dyeing time of coarse melanin can improve the dye uptake of veneers, and the brightness value increases, and the reflectivity declines with the increase of dyeing time. The stained surface of the vessel is gradually covered by coarse melanin dye, and more melanin particles can be clearly observed accumulating together on the stained surface with agar. Infrared measurements show that the absorption peak of -C=O in carboxylic acid disappears at 1740 cm-1, which can be attributed to the fact that -C=O (1776 cm-1) in an anhydride or ketone group is formed by further oxidation and condensation of agar and NaOH. The veneer dyed for 6 h showed a well light and water resistance. Additionally, dyeing can improve the wettability of water, phenolic resin, and urea formaldehyde resin on the surface of veneer. These results support the use of pigment secreted by stain fungi for wood and provide data for evaluating their use as sustainable materials for other applications.