Chiang Mai Journal of Science

 Monascus purpureus TISTR3179, with capability to promote high production of natural red pigment and anti-cholesterol agent, monacolin K, was used for solid rice culture in static flask and koji chambers. The effect of various factors on the optimal fermentation condition for 15 days incubation was determined using 500ml-flask containing 100 g rice substrate. The results indicated that incubation temperature of 30 °C and 38% (w/w) initial moisture content of rice at neural pH gave the highest red pigments and monacolin K production at 3,571.97 A₄₂₀U/gdw, 2,697.71 A₅₀₀U/gdw, and 13,536.61 mg/kgdw, respectively. While the highest glucoamylase activity and glucosamine content of 189,685.66 unit/gdw and 4.438 mg/gdw were obtained under 35°C incubation, with 38% (w/w) initial moisture content of rice substrate at initial pH 5. The secondary metabolites were drastically reduced (80-90%) at 41-43% (w/w) initial moisture content although the biomass was similar in content. Remarkably, scaling up of fermentation in the semi-automated koji chambers of 10 and 50 kg rice substrate by using information from flask level showed that M. purpureus TISTR3179 could grow and produce higher pigments and monacolin K in a shorter time. Fermented rice of 10 kg and 50 kg koji chambers produced 2 times higher pigments and 2 and 4 time higher monacolin K than those obtained from flask scale cultivation. Ready-to-use product of fermented red rice was examined for subsequent processing of storage stability. The results showed that the amount of pigments and monacolin K in red rice were stable by steaming at 100 °C 30 min for growth inactivation, drying at 50 °C overnight and storing in the refrigerator (2-4 °C) for 1.5 months.