Yeasts as biocontrol agents of Aspergillus spp producers of ochratoxin “A” in coffe: from growth to transcription of OTA biosynthetic genes

Abstract

Brazil is the largest producer and exporter of coffee in the world ranking and the State of Minas Gerais is responsible for more than 50% of this production. The microbiota of coffee fruits and beans is very diverse, but a greater concern is due to the presence of filamentous fungi, of the genus Aspergillus, producers of mycotoxins, with ochratoxin A being the most important in this culture. Biological control using antagonistic microorganisms is an alternative, as it can reduce the use of fungicides that cause various environmental and public health damages, such as poisoning farmers. In addition, understanding the mechanisms that antagonistic microorganisms employ to control the production of toxins by toxigenic fungi, as well as the best conditions for such action, is of fundamental importance for proper management, ensuring the safer production of coffee beans meeting the requirements of the world market. Given the above, the general aim of this study was to evaluate the antagonist efficiency of yeast strains on the growth of filamentous fungi of the genus Aspergillus, reported as producers of ochratoxin A in coffee, as well as the expression of genes involved in the biosynthesis of this mycotoxin when in fungus-yeast co-cultivation. For this, eighteen yeast strains that are deposited in the Collection of Cultures of Agricultural Microbiology (CCMA) of the Department of Biology and three strains of ochratoxigenic filamentous fungi belonging to the collection of Culture of Microorganisms of the Department of Food Sciences (CCDCA) of the Federal University of Lavras. The biological control mechanism was evaluated in green coffee-based culture medium. Production of volatile organic compounds (VOCs) was evaluated by gas chromatography - GC-MS, OTA was quantified by high performance liquid chromatography - HPLC and the expression of the genes of the biosynthesis of this mycotoxin was evaluated. As a result, it was possible to identify the yeast S. cerevisiae CCMA0159 as promising for the biocontrol of ochratoxigenic fungi, with the production of VOCs with fungicidal action, as well as verifying that the antagonist action also occurs at the transcriptional level, with reduced expression of all OTA biosynthetic genes, including hal and p450 .