Relationship between cyclopiazonic acid production and gene expression in Penicillium griseofulvum under dry-cured ham processing environmental conditions.

Cyclopiazonic acid (CPA)-producing Penicillium griseofulvum is usually found on the dry-cured ham surface during its ripening. The objective of this work was to evaluate the effect of temperature and water activity (aw) of dry-cured ham processing on growth, CPA production, and temporal relative expression of genes involved in CPA biosynthesis on dry-cured meat-based media. P. griseofulvum CECT 2919 grew faster than P. griseofulvum IBT 14319 in all conditions tested, although no growth occurred at 0.85 aw. Besides, the dry-cured ham-based medium favoured CPA synthesis for both strains compared to the meat-based medium. For the strain CECT 2919, the expression of the mfs-1 and pks-nrps genes were stimulated at 0.90 and 0.95 aw, respectively, while the dmaT gene expression was inhibited during the incubation time. By contrast, the strain IBT 14319 showed that the dmaT gene expression was stimulated at 0.90 aw, while the pks-nrps and mfs-1 genes were repressed throughout incubation time. In conclusion, it is necessary to reduce aw on the surface of the hams below 0.85 during ripening before to increase temperature to reduce growth of P. griseofulvum and CPA production. This information may be useful to design preventive and corrective actions to minimise risks associated with the presence of CPA in dry-cured ham.