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 ve rrucosum, IBT5010 and IBT12803, were examined in co-cultures with the antagonistic yeast Pichia anomala or baker's yeast Saccharomyces cerev isiae. Each yeast was co-cultured with Penicillium verrucosum in malt extract agar supplemented with 1% yeast extract and incubated at 25 de grees C for 14 d. Ochratoxin A was found to be stable at 25 degrees, w hether or not yeast was present. Pichia anomala and Saccharomyces cere visiae reduced mould growth to about the same extent in vitro. Both ye asts significantly reduced the growth of Penicillium verrucosum isolat es at 3 x 10(3) yeast c.f.u./plate. In all co-cultures in vitro accumu lated ochratoxin A was reduced to below the detection limit (100 ng/pl ate) 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 Penic illium verrucosum IBT12803 was clearly inhibited by this yeast. A simi lar pattern was observed for ochratoxin A accumulation in wheat when t he two mould strains were co-cultured with Pichia anomala. Mycotoxin p roduction was more sensitive to the presence of yeasts than was mould growth. Go-cultivation with yeasts gave no detectable stimulation of o chratoxin A accumulation in agar or wheat.