Ochratoxin A accumulation in cultures of Penicillium verrucosum with the antagonistic yeast Pichia anomala and Saccharomyces cerevisiae

Growth and ochratoxin A accumulation by two isolates of Penicillium verrucosum , IBT5010 and IBT12803, were examined in co-cultures with the antagonistic yeast Pichia anomala or baker's yeast Saccharomyces cerevisiae . Each yeast was co-cultured with Peniciilium verrucosum in malt extract agar supplemented with 1% yeast extract and incubated at 25 °C for 14 d. Ochratoxin A was found to be stable at 25°, whether or not yeast was present. Pichia anomala and Saccharomyces cerevisiae reduced mould growth to about the same extent in vitro . Both yeasts significantly reduced the growth of Penicillium verrucosum isolates at 3 x 10 3 yeast c.f.u./plate. In all co-cultures in vitro accumulated ochratoxin A was reduced to below the detection limit (100 ng/plate) by yeast amounts as low as 3 x 10 2 c.f.u./plate. In wheat, the growth of Penicillium verrucosum IBT5010, measured as c.f.u., was not reduced in the presence of Pichia anomala , whereas the growth of Penicillium verrucosum IBT12803 was clearly inhibited by this yeast. A similar pattern was observed for ochratoxin A accumulation in wheat when the two mould strains were co-cultured with Pichia anomala . Mycotoxin production was more sensitive to the presence of yeasts than was mould growth. Co-cultivation with yeasts gave no detectable stimulation of ochratoxin A accumulation in agar or wheat.