|Monascus purpureus growing on white rice (red yeast rice)|
Monascus purpureus (syn. M. albidus, M. anka, M. araneosus, M. major, M. rubiginosus, and M. vini; simplified Chinese: 红曲霉; traditional Chinese: 紅麴黴; pinyin: hóng qū méi, lit. "red yeast") is a species of mold that is purplish-red in color. It is also known by the names ang-khak rice mold, corn silage mold, maize silage mold, and rice kernel discoloration.
Taxonomy and morphology
The sexual state of M. purpureus is a cleistothecium with a two-layered wall enclosing round, evanescent 8-spored asci, lifted above the substrate on a multihyphal stalk. Ascospores can be heat resistant. The asexual state forms chains of hyaline or brownish chlamydospore-like cells.
Physiology and metabolites
During growth, Monascus spp. break down starch substrate into several metabolites, including pigments produced as secondary metabolites. The structure of pigments depends on type of substrate and other specific factors during culture, such as pH, temperature, and moisture content.
However, discoveries of cholesterol-lowering statins produced by the mold has prompted research into its possible medical uses. It produces a number of statins. The naturally occurring lovastatins and analogs are called monacolins K, L, J, and also occur in their hydroxyl acid forms along with dehydroxymonacolin and compactin (mevastatin). The prescription drug lovastatin, identical to monacolin K, is the principal statin produced by M. purpureus. Only the open-ring (hydroxy acid) form is pharmacologically active, but it is not produced on a commercial scale.
The mycotoxin citrinin is carefully monitored when Monascus is used in fermented foods. Industrial use of soluble red pigments as food dyes was discontinued in the USA and Europe because of this risk. 
Monascus purpureus has been used for over a thousand years in oriental fermented foods, including red kōji-kin, red yeast rice or ank-kak, rice wine, kaoliang brandy, and as the coloring agent for Peking duck.
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