Abstract
Aflatoxigenic molds can grow and produce aflatoxins on dry-fermented meat and cheese. The small, basic, cysteine-rich antifungal protein PgAFP displays a time-limited inhibitory ability against unwanted molds by increasing reactive oxygen species (ROS), which can lead to increased aflatoxin production. However, calcium abolishes the inhibitory effect of PgAFP on certain Aspergillus spp. To maximize the antifungal effect, this protein may be combined with protective cultures. Yeasts and lactic acid bacteria may counteract the impact of calcium on PgAFP fungal inhibition. The objective of this work was to study the effect of PgAFP and different combined treatments with Debaryomyces hansenii and/or Pediococcus acidilactici against growth of and aflatoxin production by an aflatoxigenic strain of Aspergillus parasiticus in both culture media and dry-fermented foods with low or high calcium levels. Aflatoxins production was increased by PgAFP but dramatically reduced by P. acidilactici in low calcium culture medium, whereas in the Ca-enriched culture medium, all treatments tested led to low aflatoxins levels. To study whether PgAFP and the protective microorganisms interfere with ROS and aflatoxin production, the relative expression of genes foxA, which is involved in peroxisomal β-oxidation, and aflP, which is required for aflatoxin biosynthesis, were evaluated. The aflatoxin overproduction induced by PgAFP seems not to be linked to peroxisomal β-oxidation. The combination of PgAFP and D. hansenii provided a successful inhibitory effect on A. parasiticus growth as well as on aflatoxin production on sliced dry-fermented sausage and cheese ripened up to 15 days, whereas P. acidilactici did not further enhance the protective effect of the two former agents. Therefore, the combined treatment of PgAFP and D. hansenii seems to provide a promising protective mean against aflatoxin-producing A. parasiticus on dry-fermented foods.
Highlights
Various microorganisms, including bacteria and fungi, decisively contribute to the specific characteristics of dry-fermented foods
A. parasiticus grew poorly in CaCl2-enriched YES (Ca-YES) broth and was further inhibited by most treatments, but not by PgAFP alone (Figure 1). Both AFB1 and AFG1 were produced in the untreated batch by A. parasiticus in both culture media (Figure 2)
In YES broth, Pg + D. hansenii alone (Dh) induced a higher AFG1 quantity whereas no statistically significant increase was obtained for AFB1 compared to the untreated control
Summary
Various microorganisms, including bacteria and fungi, decisively contribute to the specific characteristics of dry-fermented foods. The environmental conditions during the ripening of dry-fermented foods favor colonization of their surface by toxigenic molds that are able to produce mycotoxins on such foods. Aflatoxins have long been a major concern in cheese [1,2,3,4,5] and recent studies have highlighted their presence in dry-cured meats [6,7,8,9]. Aflatoxins, produced mainly by Aspergillus flavus and Aspergillus parasiticus, are classified as group 1 carcinogenic to humans by the International Agency for Research on Cancer. It is necessary to design strategies to prevent aflatoxigenic molds growth on dry-fermented foods. The use of protective cultures could provide widely accepted preventive means to control mycotoxin production in ripened foods
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