Isolation, Screening and Fermentation Optimization of Monascus Strains with High Monacolin K Yield and the Cholesterol Lowering Effect of Red Yeast Rice

Monacolin K (MK), one of the main active ingredients of red yeast rice, has cholesterol-lowering effect. This study aimed to improve MK content in red yeast rice through three aspects including strain and rice material screening and optimization of fermentation conditions. The cholesterol-lowering effect of high MK red yeast rice in mice was also studied. The results showed that: Monascus strain FG-2 has the highest MK yields, about 2.3 times of model strain ACCC 30501. Molecular identification reveals the strain as Monascus purpureus. When fermented with polished rice of variety "1a825" as substrate, strain FG-2 and the highest MK yield, about 2.7 times of commercially available rice "Dulimi" The optimum fermentation conditions for strain FG-2 were determined by single factor optimization and orthogonal test: pre-fermentation temperature at 30 degrees C, seed solution pH at 5.0, rice amount in fermentation flask 40 g, fermentation time 17 d. MK yield under this fermentation condition was 4.64 mg/g, 28.5% higher than before optimization, which was about 8.3 times of commercially available Gutian red yeast rice. The high MK red yeast rice prepared herein and commercially available Gutian red yeast rice have significant cholesterol lowering effects, with the former superior to the latter. (C) 2019 Friends Science Publishers