Monascus purpureus Growth and Secondary Metabolites: Characterization of Fungal Growth, Citrinin, Pigments, and pH during Different Growth Phases

Abstract Monascus spp. is a filamentous fungus commonly used to produce red fermented rice (RFR). Pigments extracted from Monascus spp. are currently in demand in the food industry due to many benefits to health and applications as coloring, flavoring, and preserving agents. Since citrinin (CIT) is also produced during Monascus spp. fermentation, this is raising food safety concerns. This study was designed to characterize the growth, pigments production, CIT production, and pH of M. purpureus isolates on coconut cream agar (CCA) under prolonged incubation. Two M. purpureus strains (MF1 and MS1) were isolated from RFR, inoculated onto CCA, and incubated for 30 days at 30°C. Fungal growth was determined based on colony size, fluorescence zone size, radial growth rate, and fungal biomass. During incubation, fungal growth, CIT, pigments, and pH of the extraction were determined. Two growth phases of M. purpureus were observed in this study, which were exponential (days 4–21) and stationary (days 24–30). Strong fluorescence was observed at the exponential phase together with an increase in biomass and colony diameter. CIT levels increased initially and then decreased with further incubation. Pigments production by M. purpureus increased, showing an inverse relationship with CIT decrease. The pH of the isolates on CCA increased from 7.0 to 8.6. These results provide fundamental insights into the relationship between fungal growth, CIT production, pigments, and pH during M. purpureus incubation on CCA.