Monacolin K production by citrinin-free Monascus pilosus MS-1 and fermentation process monitoring

Abstract

Monacolin K (MK) is a naturally occurring hypocholesterolemic agent that specifically inhibits HMG-CoA reductase. As a natural source of MK, Monascus-fermented products are of special interest; however, some Monascus strains could produce citrinin, which is a nephrotoxin, as a contaminant in Monascus-derived products. A Monascus pilosus strain (MS-1) that produces high amounts of MK, but no citrinin, was screened in previous investigations. Herein, liquid-state fermentation parameters of the MS-1 strain were optimized using statistical methods to maximize the MK yield with potato juice as a basic medium. The maximum MK yield (326.74 μg/mL) was predicted with 50 mL of medium in a 250-mL conical flask containing 30 g/L sucrose, 38.75 g/L soybean flour, 0.00105 mol/L Mg2+ at pH 5.48, and 8% v/v seed inoculum precultured for 42 h at 30°C, incubated at 30°C for 3 days, followed by further incubation for 11 days at 24.7°C. The verified MK yield was 390.68 μg/mL and the MK yield increased to 565.64 μg/mL after 21 days of fermentation. No citrinin was detected in MS-1-fermented products. The results suggest that citrinin-free MK can be obtained from natural medium through liquid-state fermentation in an economical way. This method will be of practical value to the industrial production of MK.