The Effect of Yeast Antagonist Isolated from the Fermentation of Cocoa Beans (Theobroma cacao) from Lampung, Indonesia, on the Growth of Aspergillus flavus UNJCC F-55

Abstract

Mold is one of the microorganisms that causes damage to cocoa fruit because it produces mycotoxins as secondary metabolites that can decrease the crop yield. One type of pathogenic mold that destroys cocoa fruit is Aspergillus flavus. A. flavus produces aflatoxin B1 which is the most potent hepatotoxin and carcinogen to humans. Amongst the most effective ways to avoid alpha-toxin contamination in cocoa beans is to inhibit the growth of A. flavus in the beans. However, the use of pesticides and fungicides can increase the development of resistant strains of fungi and have a negative impact on the environment and human health. Therefore, we need other alternatives such as bio-control agents using antagonistic microorganisms, including yeasts. Thus, this study aims to characterize yeasts isolated from the fermented cocoa beans (Theobroma cacao) from Lampung, Indonesia, and evaluate their ability to inhibit the growth of Aspergillus flavus UNJCCF-55. The methods used were yeast screening, dual culture technique for antagonistic test, and morphological characterization. The 37ºC-growth screening gave 89 out of 98 yeast isolates. The subsequent antagonist test resulted in 13 isolates with the highest inhibition zone against A. flavus UNJCCF-55. These yeast isolates were macroscopically of smooth surface, butyrous texture, milky white color, irregular edges, and convex elevation. Microscopic observation showed that the isolates have oval cell shape, asexual reproduction of budding, and non-hyphae structure.
 Keywords: yeast antagonist, cocoa fermentation, aspergillus flavus