Mycotoxin biocontrol: two examples of intra- and inter-specific biocompetition

Aflatoxins (AF) and ochratoxin A (OTA) are two of the most abundant food-contaminating mycotoxins, produced by several Aspergillus and Penicillium species; the first is considered one of the most potent hepatocarcinogenic agents in man and animals, while the latter is reported to have carcinogenic, nephrotoxic, and immunosuppressive effects in long-term exposed individuals. The natural occurrence of these mycotoxins in foods represents considerable health risk to humans. As biocontrol agents, many species of bacteria, fungi and yeasts have been tested for their ability in reducing mycotoxigenic fungi and resultant mycotoxin contamination in food and feed commodities. Regarding to biological control of aflatoxin occurring in oil-containing crops such as maize, peanut, and cottonseed, great successes have been achieved through the application of competitive atoxigenic strains of A. flavus and A. parasiticus. In meat derivatives such as salami and hams, various attempts to control the surface colonization by potential ochratoxingenic moulds have been recently carried out: use of fungi as biocontrol agents against P. nordicum seems to be a particularly promising way to improve food safety without affecting properties and sensory quality of meat products. Here two different approaches in setting and developing inter- and intra-specific biocompetition strategies to control mycotoxins in foods are discussed. A simple, hightroughput fluorescence-based procedure, suitable for assessing the AF production in the medium during fungal growth, is used to screen a closed population of Aspergilli from maize kernels sampled in the Lokobe Integral Reserve (Madagascar); an A. oryzae wild strain effective in reducing AF accumulation by aflatoxigenic strains of A. flavus and A. parasiticus during biocompetition trials performed both in a synthetic medium and on a natural substrate (corn grains). On the other side, some atoxigenic strains of P. nordicum have been analyzed for their potential in preventing/lowering OTA accumulation during biocompetition with OTA producing P. nordicum strains in YES-liquid medium. The most effective strain identified by this procedure will be used for competition experiments on cured meat (salami).