Abstract: The purpose of this study was to isolate high monacolin K-producing Monascus from Xiangxi natural savory vinegar by primary UV spectrophotometric screening and secondary high performance liquid chromatographic (HPLC) screening. The primary screening resulted in 7 Monascus strains capable of producing monacolin K, out of which strain M3 with the highest monacolin K-producing ability (achieving a concentration of 157 mg/L in fermentation broth) was isolated through the secondary screening. Further, fermentation conditions optimization for monacolin K production by strain M3 was carried out based on a mathematical model established using Box-Behnken central composite design. The optimal fermentation conditions were found to be: initial pH of 5.3, culture temperature of 25 ℃, shaking speed of 112 r/min and fermentation time of 10.5 days. Under the optimal fermentation conditions, the yield of monacolin K reached up to 354.68 mg/L.

Key words: Xiangxi natural savory vinegar, Monascus, monacolin K, strain screening, fermentation conditions