Antagonistic activity of phylloplane yeasts from Moringa oleifera Lam. leaves against Aspergillus flavus UNJCC F-30 from chicken feed

Aspergillus flavus is widely known as an aflatoxin-producing fungus that frequently contaminates feed and affects livestock, which leads to severe health problem for animal and human. Biological agents have been proven to prevent this contamination since they can produce metabolites which have antagonistic activity. In this study, phylloplane yeasts isolated from Moringa oleifera leaf have shown an ability to inhibit the growth of Aspergillus flavus UNJCC F-30 collected from chicken feed. This research was conducted in three stages: (1) yeast isolation (leaf washing and direct method), followed by (2) antagonistic test using dual culture method, and (3) molecular identification using D1/D2 region of 26S rDNA. In the first stage, 38 yeast isolates have been succesfully obtained. These isolates were of different colors: peach pigment (60.5%), the non-pigmented yeast (26.5%), cream (10%), and orange (3%). Antagonistic activity against A. flavus UNJCC F-30 was tested based on growth, sporulation, and the presence of clear zones. Screening result showed that 12 yeast isolates are capable of inhibiting A. flavus UNJCC F-30. Among them, 4 isolates with the code K4, K10, K15, and K26 showed the highest antagonist ability. Molecular identification resulted that the 4 isolates show a similar identity with Aureobasidium pullulans UWFP 993 (100%), Aureobasidium melanogenum QCC:M017/17 (99%), Aureobasidium melanogenum QCC:M017/17 (100%) and Rhodotorula taiwanensis CBS:11729 (99%), respectively. Isolate K10 exhibited the highest percentage of inhibition activity among all isolates which is potential for application as biocontrol agent against A. flavus . As A. pullulans is a common yeast found on leaf surfaces of many Indonesian flora, therefore it can be considered as safe and alternative to reduce fungal contamination from A. flavus in feed chicken.