Screening of Monascus Strains with High-yielding Monacolin K and Low-yielding Citrinin and the Optimization of Fermentation Conditions

The strains of Monascus with high-yielding monacolin K and low-yielding citrinin were screened, in order to lay a foundation for the later development and application of red koji technology. The different brands of red yeast rice from Gutian County, Fujian Province was used as raw material to isolate and purify the strains of Monascus with high-yielding monacolin K and low-yielding citrinin. Then, the fermentation conditions of pure red koji were optimized by single factor experiment. The results showed that 15 strains (M1-M15) were obtained through screening, and the contents of monacolin K and citrinin were determined by HPLC, indicating that the content of citrinin in M8 strain was 1.40 μg·g^-1, and the content of monacolin K was 3 950 μg·g^-1, which was selected as the optimal starting strain of Monascus. By further optimizing the fermentation conditions of M8 strain, it was found that under the conditions of pH value 4.5, culture temperature 25℃ and culture time 11 d, the content of monacolin K in M8 strain of Monascus was the highest, reaching 4 160 μg·g^-1. Therefore, a strain of Monascus with high-yielding monacolin K and low-yielding citrinin was screened from the experiment, thus to expand the selection of the strains with high-yielding monacolin K.