Fungi as a commercial source of eumelanin: current understanding & prospects.

Melanins represent a diverse collection of pigments with a variety of structures and functions. One class of melanin, eumelanin, is recognizable to most as the source of the dark black color found in cephalopod ink. Sepia officinalis is the most well-known and sought-after source of non-synthetic eumelanin, but its harvest is limited by the availability of cuttlefish, and its extraction from an animal source brings rise to ethical concerns. In recent years, these limitations have become more pressing as more applications for eumelanin are developed-particularly in medicine and electronics. This surge in interest in the applications of eumelanin has also fueled a rise in the interest of alternative, bio-catalyzed production methods. Many culinarily utilized fungi are ideal candidates in this production scheme, as there are examples of which have been shown to produce eumelanin, whose growth at large scales are well-understood, and can be cultivated on recaptured waste streams. However, much of the current research on fungal production of eumelanin focuses on pathogenic fungi and eumelanin's role in virulence. In this paper, we will review the potential for culinary fungi to produce eumelanin, evaluate the economic feasibility of current methods of fungal eumelanin production, and provide suggestions for new research areas that would be most impactful in the search for improved fungal eumelanin producers.