PEROXISOMAL BETA-OXIDATION ACTIVITIES AND GAMMA-DECALACTONE PRODUCTION BY THE YEAST YARROWIA-LIPOLYTICA

gamma-Decalactone is a peachy aroma compound resulting from the peroxi somal beta-oxidation of ricinoleic acid by yeasts. The expression leve ls of acyl-CoA oxidase (gene deletion) and 3-ketoacyl-CoA thiolase act ivities (gene amplification on replicative plasmids) were modified in the yeast Yarrowia lipolytica. The effects of these modifications on b eta-oxidation were measured. Overexpression of thiolase activity did n ot have any effect on the overall beta-oxidation activity. The disrupt ion of one of the acyl-CoA oxidase genes resulted in an enhanced activ ity. The enhancement led to an increase of overall beta-oxidation acti vity but reduced the gamma-decalactone production rates. This seemed t o indicate a non-rate-limiting role for beta-oxidation in the biotrans formation of ricinoleic acid to gamma-decalactone by the yeast Yarrowi a lipolytica. All strains produced and then consumed gamma-decalactone . We checked the ability of the different strains to consume gamma-dec alactone in a medium containing the lactone as sole carbon source. The consumption of the strain overexpressing acyl-CoA oxidase activity wr as higher than that of the wild-type strain. We concluded that peroxis omal beta-oxidation is certainly involved in gamma-decalactone catabol ism by the yeast Y. lipolytica. The observed production rates probably depend on an equilibrium between production and consumption of the la ctone.