Appl Microbiol Biotechnol (2008) 77:965–973 DOI 10.1007/s00253-007-1256-6 MINI-REVIEW Biologically active components and nutraceuticals in the Monascus-fermented rice: a review Yii-Lih Lin & Teng-Hsu Wang & Min-Hsiung Lee & Nan-Wei Su Received: 15 August 2007 /Revised: 24 October 2007 /Accepted: 25 October 2007 / Published online: 22 November 2007 # Springer-Verlag 2007 Abstract Monascus-fermented rice has traditionally been and vegetable pork stew. MFR is also widely used as starter used as a natural food colorant and food preservative of culture for brewing red rice wine. Several names, including meat and fish for centuries. It has recently become a Hung-Chu, Hong Qu, Ang-kak, Ankak rice, Red Yeast rice, popular dietary supplement because of many of its Red Mold rice, and Beni-Koji, are used as synonyms for bioactive constituents being discovered, including a series this food product. MFR is described as a mild folk of active drug compounds, monacolins, indicated as the 3- medicine, which has the therapeutic effect to promote the hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors health of cardiovascular system. Its pharmaceutical function for reducing serum cholesterol level. The controversy of its has been stated in the ancient Chinese pharmacopeia, Ben safety has been provoked because a mycotoxin, citrinin, is Cao Gang Mu composed by Shi-Zhen Li (1518–1593 A.D.). also produced along with the Monascus secondary metab- Monascus was classified and named in 1884 by French olites by certain strains or under certain cultivation scientist van Tieghem (1884). In 1895, Went published a conditions. This review introduces the basic production careful study on Monascus purpureus, a species discovered process and addresses on the compounds with bioactive from the samples collected by Dutch scientists in Java, functions. Current advances in avoiding the harmful where it was used largely for coloring rice (Went 1895). ingredient citrinin are also discussed. The genus Monascus is considered to belong to the family Monascaceae, the order Eurotiales, the class Ascomycetes, Keywords Koji . Metabolites . Monascus . Nutraceuticals the phylum Ascomycota, and the kingdom Fungi (Young 1930). Today, there are 58 Monascus strains deposited in the American Type Culture Collection. However, based on Introduction Hawksworth and Pit’s(1983) work on the taxonomy in 1983, most strains belong to only three species: M. pilosus, Monascus-fermented rice (MFR) is a commonly used food M. purpureus, and M. ruber. The majority of microorgan- colorant and dietary material in Asian countries. In China, ism for production of MFR is M. purpureus, which also has Japan, Taiwan, Thailand, and Philippines, MFR is used as a a synonym as M. anka Nakazawa et Sato when it was traditional additive for preserving fish and meat. Because of isolated from the rice koji in Taiwan by two Japanese its flavor, aromatic fragrance, and vivid red color, MFR is academics in 1930 (Steinkraus 1983; Su et al. 1970). frequently used as a flavoring agent for a variety of Chinese dishes. Examples of recipes using red yeast rice are roast Production of MFR pork, roast duck, fermented bean curd, preserved dry fish, The earliest documentation of the production process was : : : Y.-L. Lin T.-H. Wang M.-H. Lee N.-W. Su (*) described by Ying-Xing Song in his publication “T'ien- Department of Agricultural Chemistry, kung k’ai-wu” in the seventeenth century, which provides National Taiwan University, important guidance of koji management for the modern no. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan manufacturing (Song 1966). Contemporary method for e-mail: [email protected] producing MFR is to steam the rice grains to the status of 966 Appl Microbiol Biotechnol (2008) 77:965–973 semigelatinization (when the shape of rice kernel is remained compounds and minimal harmful ingredients (i.e., citrinin). and the grains can be pressed into flat with moderate Thus, several critical parameters that dominate the quality of pressure by fingers). After the inoculation by Monascus these MFR products are discussed as follows. starter, the rice grains are incubated in a temperature- controlled chamber and regularly flipped and damped during Solid-state fermentation the entire fermentation process, until the center of the rice becomes deep red colored. The contemporary method of MFR mass production is still Temperature and moisture are critical parameters dom- by the traditional solid-state fermentation on cooked whole inating the quality of MFR. To appropriately control both of rice kernel. Successful productions of MFR are often them, the rice grains as the fermentation substrate are determined by the following factors: the type of substrates conventionally covered by cotton clothes to maintain the (predominantly nonglutinous rice kernel), type of selected water content and heat and to dissipate them by temporary Monascus strains, temperature and moisture content of the removal of that coverage. The temperature of fermentation fermentation mixture thorough the process, and control of mixture should be maintained at 30–35°C in favor of the contamination factors (Su 2001). Until monacolins and best propagation and mycelium growth. The rice grains are GABA were reported in these products, good production flipped daily to ameliorate the heat generated from quality of MFR was long being regarded as higher pigment microbial metabolism. A regular fermentation procedure accumulation in the fermentation mixture. Juzlova et al. usually takes 7 days until the center of the rice becomes (1996) summarized several articles in a review that addressed deep red colored. The final product is traditionally sun solid-state cultivation of Monascus sp. in laboratorial scale dried or oven dehydrated at 45°C for 22 h for storage. The for pigment production. moisture content of the final product should be 10±1%, and Of the rice substrates used in producing MFR, non- each grain should easily crumble between one’s fingers glutinous soft rice was superior to glutinous rice in which (Steinkraus 1983;Su2001). the former has higher nutritious value (e.g., starch content) to the molds and is easier to absorb water (Steinkraus 1983; Advances in Monascus fermentation Su 2001). On the control of water content during MFR production, The ingredients of MFR are significantly affected by it is reported that the optimal substrate humidity should be fermentation conditions. Although manufacturers of MFR adjusted to approximately 40–50% at initial and maintained heavily rely on the experiences and the quality varies lot to by temporarily moistening the substrates in favor of fungal lot, the critical parameters in controlled cultivation had just growth (Hesseltine 1965; Su and Wang 1977). Recent been recognized. studies suggested that a lower initial moisture content The knowledge of Monascus pigment fermentation for (25–30%) helps to keep a low glucoamylase activity and, thus, substitution of natural colorants in meat products has been is benefit to the pigment yields (Lotong and Suwanarit 1990; summarized by Juzlova et al. (1996). They concluded that Teng and Feldheim 2000). However, Chen and Hu (2005) the orange pigments of extracts from submerged Monascus concluded that cultivation of a mutant strain M. pilosus cultures were responsible for not only antibacterial and M12-69 yielded the best monacolin K/citrinin ratio when the antifungal activities but also immunosuppressive, embry- water contents is between 55 and 75%. otoxic, and teratogenic effects. These samples impaired the Sufficient aeration is also a key parameter to pigment concanavalin A-stimulated proliferation of mouse spleno- production than growth. Pigment formation was dramati- cytes and human peripheral blood cells and exhibited toxic cally blocked when excess CO2 accumulated in the and teratogenic effects on chicken embryos. However, the incubator (Teng and Feldheim 2000). In the Chinese extracts from solid-state-fermented red rice seemed harm- ancient process, sufficient aeration is achievable by stirring less to chicken embryos. The antibacterial pigment was the fermentation mixture on bamboo trays every 2 h to initially discovered and named as monascidin A by Wong separate grains from agglomerates. The separation is and Bau (1977) then identified by Blanc et al. (1995) as the substantially carried out in laboratory scale by shaking the mycotoxin, citrinin (Fig. 3c). The discovery aroused the substrates in flasks or dissipating in plastic bags. Recently, attention whether cultivation methods could result in a commercial koji maker with a rotary perforated bed of dissimilar safety concerns on these products. 5-m diameter was adopted for MFR mass production Nevertheless, MFR products have been extensively com- (Chiu et al. 2006). The koji maker provides a perforated mercialized as dietary supplements to date because a variety bottom plate for up-flow aeration and a plowing mixer for of active ingredients were discovered, e.g., monacolins, γ- assisting heat removal and preventing koji agglomeration. aminobutyric acid (GABA, Fig. 3d), etc. Many efforts have To increase the beneficial ingredients and decrease the been put on producing the MFR products with higher active toxic components, random mutation to Monascus has been Appl Microbiol Biotechnol (2008) 77:965–973 967 performed and have acquired a genetically modified strain conditions for maximum pigmentation were found to be 5% with higher monacolin K productivity and lower citrinin rice powder (with 3.5% starch content) as the carbon content (Chen and Hu 2005; Wang et al. 2004). In the source, 0.5% of sodium nitrate or potassium nitrate as the culture of M. purpureus NTU 601, the addition of 0.5% nitrogen source, initial pH of 6.0, and a temperature of 32°C. ethanol as the carbon source tripled the monacolin K Su and Huang (1976) reported that polished rice powder content, elevated the GABA production to sevenfold, and gave higher pigment productions and Monascus dry weight reduced the citrinin content (Wang et al. 2003). Moreover, than rice starch, which indicates that the minor compositions substrates suitable for production of specific metabolites in rice kernel could benefit fungal growth and pigmentation.