Abstract:[Background] Red yeast rice is an edible rice koji fermented by Monascus on rice, and possess the cholesterol inhibitor monacolin K. However, commercially available red yeast rice has low levels of acid form monacolin K and generally exhibits red color, which limit its applicationl. Monascus sp. var. white 3001-18 has the advantages of not producing pigments and citrinin, but producing high levels of acid form monacolin K. [Objective] To study the effect of micronutrients on the production of monacolin K and the proportion of acid form, and also their effects on synthesis-related genes expression. [Methods] Adding different micronutrients to the solid-state fermentation medium to increase the biomass of Monascus, monacolin K production and the content of acid form. We analyzed the expression of genes related to monacolin K synthesis. [Results] The production of monacolin K improved by 10.63%, reached up to 17.90 mg/g by adding 0.1% sodium acetate. Moreover, the proportion of acid form monacolin K increased from 76.08% to 90.51% by adding 0.015% niacin. RT-qPCR analysis showed that sodium acetate increased the production of monacolin K by promoting the expression of mokA, mokB and mokC genes related to the synthesis of monacolin K. Niacin up-regulated the transcription of mokF, mokH and mokI genes, resulting in faster transport and higher proportion of acid form monacolin K. [Conclusion] Micronutrients can promote the synthesis of monacolin K by increasing the expression of synthesis-related genes. The study provides a certain theoretical basis for the application research of high producing acid form monacolin K.
