# Production of Fungal Pigments: Molecular Processes and Their Applications
## 3 Stress Factors and Fungal Pigment Production
The findings offer important insights into the evolution and adaptation of this industrially significant fungus, thereby broadening the avenues for genetic manipulation of this strain for an enhanced pigment production in the future [78]. Previous investigations with _M. purpuneus_ LPB 97 via solid-state fermentation demonstrated an alteration in pigment production and growth after treatments of high temperature and high-level salt. Specifically, exposure to a temperature over 45 \({}^{\circ}\)C was observed to induce the yield of more yellow pigments than untreated controls. A high concentration of NaCl was found to greatly stimulate red pigment production as well as to induce condiation, but with a significant decrease in biomass [116]. The impacts of temperature and salinity on fungal pigment yield and growth have also been revealed in _Talaromyces albobivreticillius_ 30548, a red-pigment-producing isolate derived from the Indian Ocean. The maximal yield of pigment was achieved in a non-salted medium, at 27 \({}^{\circ}\)C after 10 d of submerged fermentation in potato dextrose broth. However, maximal biomass production in dry weight was obtained when the medium was supplemented with 9% sea salts at the same temperature. The above results strongly suggest a positive relationship between salinity of the culture and the fungal biomass. Notably, pigment yields decreased with the elevation of salinity over 6%. Furthermore, the color distribution of fungal pigments, illustrated by the CIELAB color system, was found to depend on the salinity in the culture media. This work has unequivocally demonstrated the effects of abiotic (osmotic and thermal) stresses on the pigment production as well as the growth of marine fungi [117]. Microcolonial fungi grown in the rocks under extreme conditions such as at freezing temperatures, drought, strong UV radiation, and poor nutrients are often highly melanized [118; 119]. Examples of such fungal extremophiles include black fungi _Cryomyces antarcticus_ and _Cryomyces minteri_ in Antarctic habitats [120]. Those black fungi can produce thickened melanized cell walls in order to survive the harsh environment, whereby melanin pigments provide protection from the external stressor. Apart from cryotolerant species, melanized fungi often possess enhanced resistance to high doses of salts. Fungi such as _Hortaea werneckii, Phaeotheca triangularis, Trinmatostroma salinum, Aurebasitium pullulans_, and _Cladosporium_ spp. colonize salterns, and they are capable of withstanding high and even close-to-saturation salt levels. Melanized _H. werneckii_ cells could limit the permeability of the cell wall to glycerol, the latter of which functions as a compatible solute under saline stress, thereby reducing the flow of salt into the cell [121]. Intriguingly, sexual hormones like testosterone have effects on the melanin biosynthesis of the human pathogenic fungus _Cryptococcus neoformans_, suggesting the interaction of the host physiochemical milieu and this fungal pathogen. The work also indicated that in vivo melanization of human pathogenic species such as _C. neoformans_ is gender-biased [122]. Accordingly, this phenomenon reflects the stress responses of _C. neoformans_ towards human physiochemical status while colonizing and surviving within human tissues.