# Production of Fungal Pigments: Molecular Processes and Their Applications
## 2 Pigmented Fungi and Biosynthesis of Pigments
### Carotenoids  
'Carotene', derived from the Latin word carota, was coined in 1831 by [PERSON], who extracted and purified the orange pigment from carrot (_Daucus carota_). The names of carotenoids do not reflect their structural cues but rather are based on the stem name 'carotene', which is preceded by Greek prefixes (e.g., \(\alpha\), \(\beta\), \(\epsilon\)) that denote the two end groups [19].  
The charming colors and the health-promoting effects of various carotenoids have evoked interest in several related fields. Like carotenoids from other groups of organisms, such as plants, algae, and bacteria, carotenoids of fungal origins are known to have characteristic hues of yellow, orange, and red. This is ascribed to the ubiquitous presence, in their molecular structures, of an aliphatic polyene chain comprising eight isoprene units involving light-absorbing conjugated double bonds, the latter of which is responsible for the physicochemical traits of carotenoids [1; 20].  
Some carotenoids act as precursors of vitamin A in mammals including humans, specifically those with \(\beta\)-ring end groups, such as \(\beta\)-carotene, zeaxanthin, and \(\beta\)-cryotoxanthin [21]. Indeed, carotenoids are among the most medically significant bio-pigments. Mounting evidence has revealed that carotenoids can lower the risk of cardiovascular diseases, age-related eye disorders such as macular degeneration and cataracts [22], and cancers [1; 21; 23].  
So far, over 200 fungal species have been documented to be able to produce carotentes [24]. Carotenoid-producing fungi are very diverse, including _Rhodtorula mucaliginosa_[25], _Rhodtorula glutinis_[26], _Blakesela trispora_[27], _Phyomyces blakeselaunus_, _Mucar circineloides_, _Fusarium sportorichioides_[28], _Rhodsorporum puldigenum_, _Neurospan crassa_, and _Xanthophyllomyces dendorhous_[29]. Among them, _Blakesela trispora_ stands out as a major industrial fungus used to produce \(\beta\)-carotene as a colorant in foods, which was authorized by EU Health and Consumer Protection Directorate General in 1995 [24].  
_Blakesela trispora_ is a filamentous fungus capable of producing \(\beta\)-carotene through lycopene cyclization [30]. Lycopene is a red-colored intermediate of the \(\beta\)-carotene biosynthesis in _B. trispora_ and is converted from isopentenyl pyrophosphate (IPP, C\({}_{5}\)), the first isoprene unit of the terpenoid synthetic pathway [31]. The fungal isopentenyl pyrophosphate (IPP) is produced via the mexulonate (MVA) pathway, with acetyl-CoA as a starting precursor [1; 31].  
The early biosynthetic steps of \(\beta\)-carotene involve the sequential additions of IPP (C\({}_{5}\)) units to yield geranyl pyrophosphate (GPP, C\({}_{10}\)), farnesyl pyrophosphate (FPP, C\({}_{15}\)), and geranylgeranyl pyrophosphate (GGPP, C\({}_{20}\)) [31]. The initial compound bearing the typical aliphatic carotenoid-like structure is phytoene (a colorless molecule), converted from the condensation reaction of two GGPP units catalyzed by phytoene synthase (Figure 1). The successive step is the dehydrogenase-catalyzed conversion of phytoene to lycopene, followed by the sequential cyclization of lycopene to produce \(\gamma\)-carotene, and then to \(\beta\)-carotene, catalyzed by lycopene cyclase (Figure 1) [32; 33].