Metabolic engineering approach to boost γ-decalactone production in S. cerevisiae identifies a critical role for the peroxisomal Fatty Acyl-CoA Synthetase Faa2

Lactones constitute a family of aroma compounds found in fruits, flowers and vegetables and are in high demand in the food industry. Previous studies have reported biotransformation of castor beans-extracted ricinoleic acid to γ-decalactone using oleaginous yeast Yarrowia lipolytica. Given the potential toxicities associated with castor beans, we have used a metabolic flux-engineering approach to produce γ-decalactone from oleic acid in Saccharomyces cerevisiae. Intracellular conversion of oleic acid to ricinoleic acid was achieved by the expression of oleate hydroxylase Fah12 from ergot fungus Claviceps purpurea. Glycerol-3-phosphate dehydrogenase-mediated glycerol synthesis was identified as the major metabolic diversion of oleic acid that negatively impacts γ-decalactone yields. Chemogenomic profiling analysis revealed that the tryptophan biosynthetic pathway provides resistance to γ-decalactone-mediated toxicity in yeast. Overexpression of tryptophan transporter Tat1 enhanced γ-decalactone production by about 3- fold. Deficiency of genes encoding the cytoplasmic fatty acyl CoA synthetases FAA1 or FAA4 alone did not significantly influence γ-decalactone production. However, deficiency of peroxisomal FAA2 drastically diminished the yield of γ-decalactone. Thus, this study uncovers the metabolic barriers to oleic acid-to-γ-decalactone conversion and identifies Faa2 as an essential element in this biotransformation.