The major volatile compound 2-phenylethanol from the biocontrol yeast, Pichia anomala, inhibits growth and expression of aflatoxin biosynthetic genes of Aspergillus flavus.

摘要

Aspergillus flavus is a ubiquitous saprophyte that is able to produce the most potent natural carcinogenic compound known as aflatoxin B₁ (AFB₁). This toxin frequently contaminates crops including corn, cotton, peanuts, and tree nuts causing substantial economic loss worldwide. Consequently, more than 100 countries have strict regulations limiting AFB₁ in foodstuffs and feedstuffs. Plants and microbes are able to produce volatile compounds that act as a defense mechanism against other organisms. Pichia anomala strain WRL-076 is a biocontrol yeast currently being tested to reduce AF contamination of tree nuts in California. We used the SPME-GC/MS analysis and identified the major volatile compound produced by this strain to be 2-phenylethanol (2-PE). It inhibited spore germination and AF production of A. flavus. Inhibition of AF formation by 2-PE was correlated with significant down regulation of clustering AF biosynthesis genes as evidenced by several to greater than 10,000-fold decrease in gene expression. In a time-course analysis we found that 2-PE also altered the expression patterns of chromatin modifying genes, MYST1, MYST2, MYST3, gcn5, hdaA and rpdA. The biocontrol capacity of P. anomala can be attributed to the production of 2-PE, which affects spore germination, growth, toxin production, and gene expression in A. flavus.