Fatty acid hydroperoxide lyase (HPO lyase) is a cytochrome P450 acting on fatty acid hydroperoxides in many organisms. The expression of green bell pepper HPO lyase in the yeast Yarrowia lipolytica is described for the first time. HPO lyase activity from yeast extract and whole yeast cells is measured and aldehydes production from yeast extract and whole yeast cells is compared. 1200 U/L reaction medium were obtained after 96 h of culture on olive oil rich medium. The quantity of C6-aldehydes produced is the highest (350 mg/L reaction medium) when hydroperoxides are added directly in the culture medium supplemented with olive oil. (C) 2004 Elsevier Inc. All rights reserved.