Abstract: The purpose of this study was to screen the high Monacolin K-producing strains from 30 strains of Monascus Strain separated from natural fermented red yeast rice,and further to optimize the fermentation conditions of Monacolin K.The results showed that 9 strains of Monascus were found to produce Monacolin K by high performance liquid chromatography (HPLC) analysis.The strain No.ZX26 was the strongest strain in producing Monacolin K,and the yield of Monacolin K in the fermentation broth reached up to 107.6 mg/L.The ITS gene homology analysis showed that Monascus Strain ZX26 was Monascus purpureus.The single factor test and orthogonal test method were used to optimize the fermentation conditions of Monacolin K produced by Monascus purpureus ZX26 further.The results showed that,when the composition of the medium was glucose 70 g/L,beef extract 15 g/L,NaNO₃ 2 g/L,MgSO₄·7H₂O 0.5 g/L and KH₂PO₄ 1.5 g/L,the optimal fermentation conditions including the initial pH of 4.0,culture temperature of 30 ℃,inoculum size of 7% and fermentation time of 10 days were determined.On the optimal fermentation conditions,the yield of Monacolin K reached up to 271.36mg/L,which increased by 152.19% compared with the production of Monacolin K before optimizing fermentation conditions,It was proved that the Monacolin K yield was the best under this cultivation condition.

Key words: Monascus strain, Monacolin K, high performance liquid chromatography, orthogonal experiment