Effect of a magnetic field on the production of Monascus pigments and citrinin via regulation of intracellular and extracellular iron content

This study aims to elucidate the influences of magnetic fields (MFs) on the production of Monascus pigments (MPs) and citrinin by modulating both the intracellular and extracellular iron content in Monascus purpureus. The organism was treated with varying concentrations of L-allylglycine (L-AG), along with MFs of different intensities for 2 days during the early fermentation phase, as well as combinations of 1 mM L-AG and the MFs. The primary indicators assessed were the biomass, MPs production, citrinin production, and intracellular and extracellular iron content. The results indicate that exposure to MFs of varying intensities had no significant effect on the biomass of M. purpureus, while it significantly inhibited citrinin production. Conversely, exposure to a 1.6-mT MF significantly enhanced MPs production, while exposure to a 1.2- or 1.6-mT MF promoted the extracellular excretion of intracellular iron. Further, concentrations of 3 and 5 mM of L-AG significantly inhibited the growth of M. purpureus, whereas different concentrations of L-AG significantly inhibited MPs and citrinin production. Moreover, following treatment with both L-AG and MFs, all combinations exhibited a significant increase in MPs and citrinin production compared to L-AG treatment alone. In contrast, citrinin production in the group treated by L-AG with either a 1.2-mT or a 1.6-mT MF was significantly lower than that in the control group. Furthermore, intracellular iron content in the group treated by L-AG and a 1.6-mT or a 2.0-mT MF was reduced compared to that in the L-AG treatment group, with no significant difference from the control group. These findings suggest that appropriate exposure to MFs can decrease intracellular iron content and mitigate reductions in MPs and citrinin production induced by L-AG. Therefore, the regulation of MPs and citrinin synthesis induced by MFs in M. purpureus may be related to the intracellular iron content.