Aromatic compounds, such as cinnamic, p coumaric (4 hydroxycinnamic), and ferulic (4 hydroxy 3 methoxycinnamic) acids, have antimicrobial activity toward microorganisms, including yeast and fungi. To evaluate the mechanism for ferulic acid tolerance in Saccharomyces cerevisiae , mutants which could grow in medium containing 0.08%(w/v) ferulic acid were isolated and characterized. The Saccharomyces ccwrisiac strain X 2180 1 11 ( MATα ) was treated with ethylmethane sulfonate and selected on 0.5% malt extract, 0.01% yeast extract agar medium (MYE) containing 0.8 g per ferulic acid. By primary screening in M YE liquid medium containing 0.08% 4; ferulic acid and by secondary screening on the same agar medium, two mutant strains, designated α 1 and α 2, were isolated and further characterized. The two mutants were insensitive to the cell wall lysis enzyme Zymolyase 20 T and to cycloheximide, but were sensitive to cerulenin. The two mutants also converted ferulic acid into 4 vinylguaiacol, and the decarboxylase activity of the mutants was greater than that of the wild type, the wine yeast strain W 1, and the sake yeast strain Kyokai No.7. These results suggest that the decarboxylation of ferulic acid by biotransformation is related to the ferulic acid tolerance.