Decontamination of aflatoxin-forming fungus and elimination of aflatoxin mutagenicity with electrolyzed NaCl anode solution
2002
Suzuki, T. | Noro, T. | Kawamura, Y. | Fukunaga, K. | Watanabe, M. | Ohta, M. | Sugiue, H. | Sato, Y. | Kohno, M. | Hotta, K.
Electrolysis of a 0.1% (17.1 mM) solution of NaCl using separate anode and cathode compartments gives rise to solutions containing active chemical species. The strongly acidic "anode solution" (EW(+)) has high levels of dissolved oxygen and available chlorine in a form of hypochlorous acid (HOCl) with a strong potential for sterilization, which we have investigated here. Exposing Aspergillus parasiticus at an initial density of 10(3) spores in 10 microliter to a 50-fold volume (500 microliter) of EW(+) containing ca. 390 micromol HOCl for 15 min at room temperature resulted in a complete inhibition of fungal growth, whereas the cathode solution (EW(-)) had negligible inhibitory effects. Moreover, the mutagenicity of aflatoxin B1 (AFB1) for Salmonella typhimurium TA-98 and TA-100 strains was strongly reduced after AFB1 exposure to the EW(+) but not with the EW(-). In high-performance liquid chromatography analysis, the peak corresponding to AFB1 disappeared after treatment with the EW(+), indicating decomposition of the aflatoxin. In contrast, the routinely used disinfectant sodium hypochlorite, NaOCl, of the same available chlorine content as that of EW(+) but in a different chemical form, hypochlorite (OCl(-)) ion, did not decompose AFB1 at pH 11. However, NaOCl did decompose AFB1 at pH 3, which indicated that the principle chemical formula to participate in the decomposition of AFB1 is not the OCl(-) ion but HOCl. Furthermore, because the decomposition of AFB1 was suppressed by pretreating the EW(+) with the OH radical scavenger thiourea, the chemical species responsible for the AFB1-decomposing property of the EW(+) should be at least due to the OH radical originated from HOCl. The OH in EW(+) was proved by electron spin resonance analysis.
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