Addition of genistein to the fermentation process reduces citrinin production by Monascus via changes at the transcription level.

Monascus, which is traditionally used in various Asian industries, produces several secondary metabolites during the fermentation process, including citrinin, a toxin whose impact limits the development of the Monascus industry. We have previously found that the addition of 2.0 g/L genistein to Monascus medium reduces citrinin production by approximately 80%. Here, we explored the molecular mechanisms whereby genistein affects citrinin production. We sequenced the Monascus genome and performed transcriptome analysis on genistein-treated and -untreated groups. Comparison between the two groups showed 378 downregulated and 564 upregulated genes. Among the latter, we further examined the genes related to citrinin biosynthesis and quantified them using quantitative real-time polymerase chain reaction (qRT-PCR). Genes orf5, pksCT, orf3, orf1, orf6, and ctnE were significantly downregulated, demonstrating that genistein addition indeed affects citrinin synthesis. Our results may lay the groundwork for substantial improvements in the Monascus fermentation industry.