Abstract: We explored the effects of low-frequency magnetic field (LF-MF) on the production of ergosterol by fermentation with Monascus purpurcus and further determined the optimal LF-MF treatment conditions such as LF-MF intensity, time treatment time and the fermentation stage when M. purpurcus was treated with LF-MF on ergosterol production by liquid-state fermentation of M. purpurcus. We also investigated the effects of LF-MF on the metabolism of ergosterol by M. purpurcus, and examined the change in M. purpurcus biomass throughout the fermentation period and the effects on other main metabolites of M. purpurcus under optimal treatment conditions. Results showed that ergosterol yield was 7.08 mg/g and the biomass of M. purpurcus was 3.2 g/L on the 12th day of fermentation, which were respectively increased by 62.5% and 31.68% as compared to that of the control when M. purpurcus was treated by LF-MF at an intensity of 1.2 mT during the first two days of fermentation. Consequently, LF-MF was an effective method to enhance ergosterol yield. This result may provide evidence supporting the use of LF-MF to improve the production of beneficial microbial metabolites by fermentation.

Key words: low-frequency magnetic field (LF-MF), Monascus purpurcus, biomass, ergosterol, liquid-state fermentation