Use of yeasts in biological control of toxigenic fungy.

CHULZE, S.N.; PONSONE, M.L.; SCHMIDT-HEYDT, M.; GEISEN, R.; KÖHL, J.

Rotterdam

Congreso; 7th conference of the World Mycotoxin Forum adn XIIIth IUPAC International Symposium on Mycotoxins and Phycotoxins.; 2012

IUPAC

Pathogens and toxigenic fungi can damage a wide range of food commodities both at pre-harvest and at post-harvet stage. Ochratoxin A (OTA) is a mycotoxin produced by species that belong mainly to the Aspergillus and Penicillium genera and occurs on different commodities such as cereals, coffee, cocoa beans, dried fruits, grapes and wine. Aspergillus carbonarius is the main species responsible for OTA contamination in grapes. The development of resistance to fungicides by major plant pathogens and toxigenic fungi, and the public concern over chemical residues in food and in the environment have increased the interest in alternative methods for disease control. Biological control has been proposed as a strategy to reduce the impact of ochratoxigenic species. Yeasts are considered one of the most potent biocontrol agents due to their biology and non toxic properties. The mechanism most probably involved in biocontrol of filamentous fungi by yeasts is competition for essential factors, such as nutrients and space. Candida guillermondii and Acremonium cephalosporium were efficient in reducing decay caused by Botrytis, Rhizopus and Aspergillus in grapes. In addition, Issatchenkia orientalis have a strong antagonistic action against ochratoxigenic species; moreover, also an isolate of Metschnikowia pulcherrima and an isolate of Candida incommunis that also significantly reduced A. niger and A. carbonarius growth both in vitro and in situ were identified. Aureobasidium pullulans was effective in reducing sour rot infection, A. carbonarius presence on berries at harvest and OTA contamination in must. We have demonstrated that two epiphytic strains of Kluyveromyces thermotolerans (Lachancea thermotolerans) were able to control the growth and OTA accumulation by ochratoxigenic fungi both “in vitro” and “in situ”. Also the effect of K. thermotolerans strains on the expression of the ochratoxin pks gene, and ochratoxin A production by A. carbonarius was evaluated. K. thermotolerans strains have a strong influence on the pks gene expression. The results showed that the production of OTA can be regarded as an adaptation imposed by abiotic and other stress conditions to A. carbonarius.