Abstract:  In order to screen out low citrinin yield strain, as a starting strain, the high-yield lovastatin Monascus strain M50-2 was treated by ultraviolet, which was selected by N+ ion beam mutagenesis. The starting strain was irradiated at 30 cm under a 30 W UV lamp, and the dose was 30, 60, 90, 120 and 150 s. The contents of citrinin and lovastatin in the fermentation products were determined by high performance liquid chromatography (HPLC) with fluorescence detection (λex=331 nm, λem=500 nm) and ultraviolet detection (λ=238 nm) after the liquid fermentation of the screened mutagenized strain. The results showed that an excellent strain M120-1 was obtained by ultraviolet mutagenesis. The best strain M120-1 yielded 2.15 mg/L citrinin, which was 96.6% lower than the original strain. However, lovastatin production was 0.338 mg/mL, which was only decreased by 16.5%. To examine the genetic stability of M120-1, the strain was continuously sub-cultured to the 12th generation, showing that the strain had good genetic stability.

Key words: Monascus, citrinin, lovastatin, ultraviolet mutagenesis, composite mutagenesis