Screening and identification of Monascus strains with high-yield monacolin K and undetectable citrinin by integration of HPLC analysis and pksCT and ctnA genes amplification

Aims: Red yeast rice (RYR), produced by inoculating Monascus strains to steamed rice, contains many kinds of physiologically bioactive compounds, among which monacolin K can be used as an antihypercholesterolaemic agent. However, RYR can be polluted by the mycotoxin citrinin, which has nephrotoxic and hepatotoxic activities. To avoid the risk of citrinin contamination in Monascus fermented products, it is important to screen for Monascus strains that produce no or low citrinin.

Methods and results: Five autochthonous Monascus strains with high-yield monacolin K and undetectable citrinin were obtained using high-performance liquid chromatography (HPLC). All five strains were identified as Monascus ruber based on Genealogical Concordance Phylogenetic Species Recognition criteria. Polymerase chain reaction revealed that citrinin polyketide synthase (pksCT) gene was found in these strains, but transcriptional regulator (ctnA) was not found.

Conclusions: Five strains are potential strains for producing high-quality RYR. The distribution of the pksCT gene was not restricted to Monascus purpureus and Monascus sanguineus, and M. ruber strains were diverse in pksCT and ctnA genes.

Significance and impact of the study: The integration of citrinin HPLC analysis and pksCT and ctnA genes amplification could provide a complementary approach in valuable Monascus strains screening.