A small group of soft rotting wood decay fungi produce extracellular pigments as secondary metabolites in response to stress and as a means of resource capture. These fungi are collectively known as "spalting fungi" and have been used in wood art for centuries. The pigments produced by these fungi are finding increasing usage in industrial dye applications and green energy but remain problematic to grow in batch culture. Additionally problematic is that the pigments, especially the blue-green pigment known as xylindein, produced by Chlorociboria species, have yet to be fully synthesized. In order to further research development of these pigments and find success in areas such as textile and paint dyeing, wood UV protection, and organic photovoltaic cells, methods must be developed to mass produce the pigments. To date, three distinct methods have been developed, with varying degrees of success depending upon the fungal species (amended malt agar plates, shake liquid culture, and stationary liquid culture). This chapter details these three methods, their history, advantages and disadvantages, as well as their potential for industrial scale-up in the future. Graphical Abstract.
Keywords: Chlorociboria spp.; Fungal dyes; Fungal pigments; Scytalidium cuboideum; Scytalidium ganodermophthorum; Secondary metabolites; Spalting; Zone lines.