Combinatorial effects of UVC irradiation and peroxymonosulfate on the inactivation of <i>Aspergillus flavus</i> and aflatoxin B₁ accumulation

Abstract

<i>Aspergillus flavus</i> and its mycotoxin aflatoxin (AF) are widely present in the environment and cause various acute and chronic diseases in humans and animals. UV irradiation has been a versatile method for disinfecting <i>A. flavus</i> and detoxifying AFs. Combined effects of UV and other agents were scarcely tested yet. Here, we investigated the combinatorial effects of UVC and peroxymonosulfate (PMS) on the disinfection of <i>A. flavus</i> and accumulation of AFB₁ under aqueous conditions. UVC efficiently disinfected <i>A. flavus</i> in a dose-dependent manner. PMS (~4 mM) exhibited no disinfection but enhanced the inactivation activity of UVC. Notably, PMS or UVC (72 J/cm²) increased the accumulation of AFB₁ in the mycelia. Higher (144 J/cm²) doses of UVC suppressed AFB₁ accumulation. At the genetic level, PMS and UVC upregulated the expression of the AF biosynthetic genes <i>aflS</i> and <i>aflR</i>. In contrast, UVC degraded AFB₁ <i>in vitro</i>, which was enhanced by PMS treatment. The <i>in-vivo</i> and <i>in-vitro</i> studies indicated that AFB₁ accumulation may be compromised by the dual effects of UVC and PMS on the upregulation of AF biosynthesis and degradation activities. In conclusion, PMS and UVC are efficient disinfecting agents against <i>A. flavus</i> but also stimulate AF biosynthesis under moderate treatment conditions.