Some Biological Characteristics of Monascus Strains Isolated from a Commercial Red Fermented Rice Product

Abstract

Monascus purpureus has been widely used for over 1000 years in Asian countries especially in China and Japan for the production of natural food colorants or red fermented rice. However, M. purpureus produces a mycotoxin named citrinin. Therefore, Monascus strains used in industry must be controlled for the ability of citrinin production. In Vietnam, red fermented rice products are imported and widely sold on online markets but there are no reports on their safety. From a commercial red fermented rice sold in Vietnam, two strains of M. purpureus were successfully isolated, purified, and identified based on morphological characteristics and sequencing of the internal transcribed spacer (ITS) region of rDNA. Additionally, both isolates produce citrinin, a harmful mycotoxin, similar to the reference strains of M. purpureus. Effects of nitrogen sources and initial pH values on the production of pigments and citrinin in these Monascus strains were also investigated. The results revealed the red fermented rice product containing the citrinin-producing M. purpureus strains needed to be managed, evaluated, and monitored more strictly in terms of food safety. Notably, changes in nitrogen sources and initial pH values for fungal cultivation could suppress the toxin production for the quality improvement of red fermented rice products. In addition, two isolates provided in this study are potential strains for pigment production with strict control of fermented conditions.