Aspergillus versicolor as producer of known and novel aflatoxin precursors on hard cheese

Although, mycotoxins like sterigmatocystin (STC) and ochratoxin A (OTA) have been identified as regular contaminats in grated grana-type cheeses, limited research has been conducted to determine the responsible fungi. In 7 out of 9 grated grana-type cheese samples STC was detected by HPLC-MS/MS analysis, with two of these also containing OTA. Notably, methoxy-STC was detected for the first time in food matrix, raising concerns due to the toxic and mutagenic effects similar to those of STC, highlighting important implications for food safety. The mycobiome analysis of fungi isolated from cheese confirmed Aspergillus versicolor as the main producer of STC. An inoculation experiment using grated Parmigiano Reggiano and the isolated A. versicolor strain confirmed the production of STC together with some biosynthetic precursors. Furthermore, these results suggest that environmental factors and substrate composition influence mycotoxin biosynthesis and might have an impact beyond genetic predispositions. However, OTA was not detected in the inoculation experiment, suggesting that the presence of additional mycotoxins in grated grana-type cheese originated from further fungal co-contamination. • Detection of sterigmatocystin and ochratoxin A in grana-type cheese with HPLC-MS/MS. • First detection of mutagenic methoxylated sterigmatocystin in food. • Aspergillus versicolor identified as main sterigmatocystin producer in grated cheese. • Matrix strongly influences the mycotoxin production of Aspergillus versicolor .