Yeasts prevent ochratoxin A contamination in coffee by displacing Aspergillus carbonarius

Abstract

To cope with post-harvest diseases, chemical fungicide has not assured safe food, both due to the lack of residual protection and the increasing demand for pesticide-free agricultural products. Alternative disease control products, therefore, are essential to deal with post-harvest diseases. One alternative is using yeasts as biocontrol agents. The biocontrol mechanisms of yeasts belonging to the genera Candida, Meyerozyma, Pichia, Wickerhamomyces, Rhodotorula and Saccharomyces in vitro and in vivo pathways were investigated. For toxin killer assay, 11 of the 32 strains had the phenotype. Eight of the tested strains produced volatile organic compounds (VOCs) inhibitory to Aspergillus ochraceus CCDCA 10612 and seven to A. carbonarius CCDCA 10608. Those belonging to Saccharomyces spp produced VOCs that hampered spore production and mycelial growth of those plant pathogens. The strains of S. cerevisiae CCMA (0159; 1299; 1302) were the most efficient to inhibit ochratoxigenic fungi in vitro. S. cerevisiae strains showed similar efficiency in in vivo biocontrol assays, including ochratoxin A (OTA) reduction in beans ranging from 0.04 to 10.11 μg/Kg. The formation of biofilms by S. cerevisiae CCMA 0159 and 1302 in surface of coffee beans was observed. The population of A. carbonarius (0.5 log spores/g) was reduced in the presence of S. cerevisiae CCMA 1302 at end of the drying period. Therefore, S. cerevisiae CCMA 1302 is a candidate for biological control agent over ocratoxigenic fungi in coffee fruits.