Isolation, selection and evaluation of antagonistic yeasts and lactic acid bacteria against ochratoxigenic fungus Aspergillus westerdijkiae on coffee beans.

Unlabelled: In this study, yeasts and lactic acid bacteria (LAB) were isolated from coffee fruits and identified via biochemical and molecular approaches. The isolates represented the Pichia, Debaryomyces, Candida, Clavispora, Yarrowia, Sporobolomyces, Klyveromyces, Torulaspora and Lactobacillus genera. Four isolates, namely Pichia fermentans LPBYB13, Sporobolomyces roseus LPBY7E, Candida sp. LPBY11B and Lactobacillus brevis LPBB03, were found to have the greatest antagonist activity against an ochratoxigenic strain of Aspergillus westerdijkiae on agar tests and were selected for further characterization. Applications of P. fermentans LPBYB13 in coffee cherries artificially contaminated with A. westerdijkiae showed efficacy in reducing ochratoxin A (OTA) content up to 88%. These results highlight that P. fermentans LPBYB13 fulfils the principle requirements of an efficient biological control of aflatoxigenic fungi in coffee beans and may be seen as a reliable candidate for further validation in field conditions.
Significance and Impact of the Study: Studies based on microbial ecology and antagonistic interactions are important for the development of new strategies in controlling aflatoxin contamination of crops and are relevant to further biotechnological applications. This study shows that coffee fruit is a potential source for the isolation of microbial strains with antifungal ability. A new yeast strain, Pichia fermentans LPBYB13, showed efficacy in reducing growth and ochratoxin A production of Aspergillus westerdijkiae in coffee beans. Our results should encourage the use of this yeast strain on a large scale for biocontrol of aflatoxigenic fungi in coffee beans.
(© 2015 The Society for Applied Microbiology.)