Historic and charming <italic>Monascus</italic> spp.

Monascus species are well-known as fermentation strains in food and pharmaceutical industries in China. Monascus spp. have a long application history for more than 2000 years. Red mold rice (RMR), also known as anka and Hongqu in China, is the fermented product of steamed rice inoculated with certain Monascus strains. Nowadays, RMR and its related products have been extensively applied in food and medicine industries. In these RMR products, Monascus strains produce two kinds of the most well-known secondary metabolites (SMs) Monascus pigments (MPs) and monacolin K (MK). MPs have been employed as natural food colorant in Southeast Asia over one thousand years. MK (also known as lovastatin), an anticholesterol compound, has been developed to be a hypolipidemic drug and food supplements. Today, RMR and its relative products mainly yielded in China are not only applied in Southeast Asia, but also exported to Europe and America. It is estimated that more than one billion people, around the world, eat RMR and other relative products in their daily life. Therefore, Monascus species are considered as one of the historic and charming fermentation strains in China. Theoretical researches and product development of Monascus strains have attracted wide attention and made fruitful scientific achievements, especially in recent 30 years. In-depth studies regarding RMR have revealed that Monascus spp. not only produce beneficial SMs, MPs and MK, but also a mycotoxin citrinin (CIT). A substantial amount of researches has been successfully made to elucidate the biosynthetic pathways of these SMs and their regulation mechanism. These achievements not only serve as models of fungal SMs biosynthesis, but also provide a roadmap for metabolic engineering and synthetic biology towards the selective production of the more valuable components. Furthermore, Monascus spp. also are unique objects for researching fungal reproduction regulation and magnetic and/or light responses because Monascus spp. are found to be significantly different from the known filamentous fungi in these two fields. The progress on reproduction regulation of Monascus spp. revealed that the well-established conidiation central regulation in Aspergillus species is not applicable in their Monascus relatives. On the other hand, M. ruber M7 genome contains one red-light and two green-light receptors, but not any blue-light receptor ortholog is present in M. ruber M7 and other Monascus species, indicating a biologically significant difference between Monascus species and other filamentous fungi. Because of the unique reproduction mechanism, light and magnetic response and abundant SMs biosynthesis of Monascus spp., it is expected to enrich the theoretical understanding of filamentous fungi and even the biological world through further research on Monascus spp. Therefore, it demonstrates a great potential for developing Monascus spp. into a model microorganism. The key discussions and future prospects are also proposed from the aspects of faced challenge on Monascus spp. investigation and their products development.