Mechanisms underlying the effect of commercial starter cultures and a native yeast on ochratoxin A production in meat products

Processed meat products are of worldwide importance, but they are highly prone to fungal and ochratoxin A (OTA) contamination. In previous studies, several Lactic Acid Bacteria (LAB) and yeasts have been tested as biocontrol agents against P. nordicum growth and OTA production in meat products, with promising results. However, A. westerdijkiae has been poorly studied for this matrix. The aim of this work was to evaluate in vitro the mechanisms underlying the effects of a commercial starter culture and of a meat-native Candida zeylanoides strain on the growth and OTA production of P. nordicum and A. westerdijkiae, by co-culture in ham and sausage-based media under different conditions. In ham medium, C. zeylanoides live cells, cell broth and diffused compounds significantly inhibited OTA production by P. nordicum, but live cells of the starter culture significantly increased it. For A. westerdijkiae strong and significant stimulation was observed by direct contact in both media. In conclusion, ochratoxigenic fungi do not all respond to antagonistic microorganisms in the same way. This study sheds some light on the mechanisms behind the different effects of microorganisms.