In vitro selection of epiphytic yeasts as potential biocontrol agents against Aspergillus section Nigri

PONSONE, M.L.; CHIOTTA, M.L.; COMBINA, M.; DALCERO, A.M.; CHULZE, S.N.

Tulln, Viena, Austria

Congreso; ISM conference 2009; 2009

Ochratoxin A (OTA) is a widely distributed mycotoxin produced by several fungal species of Aspergillus and Penicillium genera. This toxin has nephrotoxic nephrocarcinogenic, teratogenic and immunosupresive effects. The presence of Aspergillus section Nigri, mainly A. niger Tiegh., aggregate and Aspergillus carbonarius (Bainier) Thom, and OTA occurrence have been observed in grapes harvested in different grape growing areas from Argentina. The OTA presence on grapes is of concern due to the possibility of wine contamination with the toxin, being wine a significant contributor for human OTA exposure. One of the strategies to reduce the entry of OTA in the food chain could be to use biological control agents at the pre-harvest stage. Epiphytic yeasts were isolated from grapes harvested in Argentinean vineyards. The strains were identified by molecular methods. The effect of yeasts on lag phase, growth rate and OTA production by Aspergillus section Nigri was evaluated in a 3% must agar based medium under different conditions of water activity (0.995; 0.982; 0.971 aW) and temperature (20 and 25 ºC), these conditions were selected considering the water activity of grapes during the maturation stages and the range of temperatures during grapes season. The growth rate and the lag phase were influenced by all the interactions evaluated (p< 0,05). Ochratoxin reduction was observed in the fungal interactions with three yeast strains, which were identified as Kluyveromyces thermotholerans. Studies are in progress to evaluate these strains under field conditions.