Production of weak acid by anaerobic fermentation of soil and antifungal effect.

Acetic acid and butyric acid were produced by the anaerobic fermentation of soil mixed with wheat or rice bran. The concentration of acetic acid produced in the wheat and rice bran-treated soil was 31.2 mM and 8 mM, respectively, whereas the concentration of butyric acid in the wheat and rice bran-treated soil was 25.0 mM and 8 mM, respectively. The minimal fungicidal concentration (MFC) for all the fungal strains was 40-60 mM acetic acid, 20-40 mM butyric acid, and 40-60 mM mixture of acetic acid: butyric acid (1:1, v/v). Consequently, the efficacy of mixing wheat-bran with soil to control soil diseases was demonstrated.