Identification and antagonistic activity screening of yeasts isolated from fermented cassava against Aspergillus niger

Aims: Cassava is a widely consumed food source in tropical regions, and its fermentation process involves various microorganisms, including yeasts that may possess valuable properties.Some yeast strains can produce antagonistic compounds against phytopathogenic fungi that include Aspergillus niger, which is a common fungal pathogen that infects various plant crops.This study aimed to isolate yeast strains from fermented cassava and screen for their antagonistic activity against A. niger, followed by the identification of the antagonistic yeast isolates.Methodology and results: Fresh sweet cassavas were fermented and used as the source for yeast isolation.Isolated yeasts were screened for antagonistic activity against A. niger using the conventional dual culture assay that involved the direct growth of a yeast isolate and A. niger on the same PDA plate.Five yeast strains were successfully isolated from fermented cassava, and one strain, designated as CAS4, exhibited positive antagonistic activity against A. niger.The conventional dual culture assay showed a growth inhibition rate of 15.2 15.8%.Identification of the antagonistic yeast was carried out using amplification and sequencing of the internal transcribed spacer (ITS) region and phylogenetic analysis, which identified the CAS4 yeast isolate as Yarrowia lipolytica.Conclusion, significance and impact of study: Aspergillus niger is a common fungal pathogen that may lead to substantial economic losses of various plants.The isolated Yarrowia lipolytica (CAS4) has the potential to be further characterized for its role as a candidate biocontrol agent for managing fungal diseases caused by A. niger in plant crops and can be further tested against other phytopathogenic fungi.This can be a promising alternative to the harmful chemical approach in controlling plant fungal pathogens.