# Production of Fungal Pigments: Molecular Processes and Their Applications
## 2 Pigmented Fungi and Biosynthesis of Pigments
### Azaphilones  
Azaphilone pigments are a structurally diverse group of fungal pigments. They are polyketide derivates, that is, pigments with pyrone-quinone structures encompassing a highly oxygenated bicyclic core and a chiral quaternary center [65; 66; 67]. Azaphilones are structurally diverse due to the easy insertion of nitrogen. The azaphilone-producing fungi are widespread in nature, including microscopic fungi (also called \"mold\"), such as species in genera _Penicillium_, _Monascus_, _Chaetomium_, and _Talaromyces_, as well as fungi devoid of mold appearance such as those in genera _Hyroxylon_, _Daldinia_, _Creosphaeria_ (members of the Xylariaceae family), and _Bulgaria_ (Bulgariaceae). Among these genera, _Monascus_ is the best known and has provided colorants for human use for over two thousand years. Azaphilone pigments give rise to yellow, red, or green hues of fruiting bodies and/or mycelia. The genus _Monascus_ includes three species: _M. pilosus_, _M. purpureus_, and _M. ruber_. They make up most food colorant strains in Asian food [24]. _Monascus_ pigments generally consist of six major azaphilone pigments: anakfalavin and monascin (yellow), monascorubrin and rubropunctatin (orange), as well as monascorubramine and rubropunctamine (violet). However, some strains of _Monascus_ spp. can co-produce citrinin, a mycotoxin displaying hepatotoxic and nephrotoxic effects on humans [68]. Hence, traditional food colorants from Asia (the so-called _Monascus_ pigments) are banned in the European Union (EU) and the United States, and there have been disputes over their safety when used in food. Strain selection and modification (via genetic manipulation) for citrinin-nonproducing _M. purpureus_ is of importance for the commercial production of _Monascus_ pigments in the food industry as well as that of monacolin K (viz. lovastatin, an anti-hypercholestrolemia drug) in the pharmaceutical industry. This list of azaphilone producers is being extended to include more fungal species. These additional fungi include _Phomopsis_ sp. (an endophytic strain producing phomposones A-C, [69]), _Pseudolanolenetra adversariala_ (an aquatic fungus producing pseudohalonectrin A-B, [67]), _Apergillus niger_ ATCC 1015 (a type strain of _A Aspergillus_ producing Azanigerones B-C, [70]), _Apergillus fumigatus_ 14-27 (a ggoronian-derived _Apergillus_ producing pinophil B, [71]), _Fusarium_ sp. (an endophytic fungus producing fusarone, [72]), _Xylariales_ sp. PSUES163 (seagrass-derived fungus producing xylariphilone [73]), _Coniella fragariae_ (goose dung-derived fungus producing coniellins H and I [74]), _Dothideomycete_ sp. (an endophytic strain producing austdiol [75]), _Cladosporium perangustsm_ FS62 (marine sediment-derived fungus producing perangustols A and B, [76]) and _Pleosporales_ sp. (a marine-derived fungus producing pleosporalone A [77]). _Monascus_ azaphilone pigments (MonAzps) are known to be synthesized via a polyketide pathway, where polyketide synthase (PKS) and fatty acid synthase (FAS) play vital roles [78]. The sophisticated biosynthetic pathway in _Monascus_ fungi is considered as a model system to elucidate and dissect the biosynthesis of fungal azaphilone pigments (Figure 4). _M. purpureus_ is one of most widely used industrial strains in different areas of China for manufacturing food colorants, while in Japan it is the only authorized species for food use [79]. In _Monascus_ _purpureus_, the main pathway of MonAzps biosynthesis starts with a non-ribosome PKS enzyme termed MpPKS5, which consists of six essential domains: acyl carrier protein transacylase (SAT), ketoacyl synthase (KS), acyltransferase (AT), product template (PT), acyl carrier protein (ACP), and reductive release (R) domain (Figure 4). The multifunctional MpPKS5, aided by a serine hydrolase encoded by _mppD_, has been found to produce a highly reactive intermediate, namely hexaketide benzaldehyde.