Unravelling the modes of action of autochthonous staphylococci against Aspergillus westerdijkiae and the antiochratoxigenic effect in dry-cured ham

Abstract

Aspergillus westerdijkiae is well known for its capacity to produce high amounts of ochratoxin A (OTA) in dry-cured ham. Some autochthonous microorganisms, such as Staphylococcus xylosus FHSCC Sx8 and Staphylococcus equorum FHSCC Se31 have antifungal effect and can be used as biocontrol agents (BCAs) to reduce the OTA contamination. The aims of this work were to reveal their modes of action against A. westerdijkiae MUM 16.142 in a dry-cured ham model system and validate the antifungal effect in dry-cured ham. As well as to assess the effect of live cells, dead cells, and cell-free broth; the pattern of nutrient use, the niche overlap index (NOI), interactions by dual culture assays, the antifungal activity of volatile compounds, and their effect on the fungal proteome. Both cocci in the dual-culture assay were able to decrease the A. westerdijkiae growth, but only S. xylosus reduced the OTA production at 20 °C. Moreover, changes in the abundance of proteins related to cell wall integrity, secondary metabolite production and carbohydrate metabolism were observed. Furthermore, the anti-A. westerdijkiae effect of S. xylosus was validated in dry-cured ham since this coccus was able to reduce the OTA production in this meat product.