Bacterial Biotransformation of Oleic Acid: New Findings on the Formation of γ-Dodecalactone and 10-Ketostearic Acid in the Culture of

Microbial conversion of oleic acid () to form value-added industrial products has gained increasing scientific and economic interest. So far, the production of natural lactones with flavor and fragrance properties from fatty acids by non-genetically modified organisms (non-GMO) involves whole cells of bacteria catalyzing the hydration of unsaturated fatty acids as well as yeast strains responsible for further β-oxidation processes. Development of a non-GMO process, involving a sole strain possessing both enzymatic activities, significantly lowers the costs of the process and constitutes a better method from the customers' point of view regarding biosafety issues. Twenty bacteria from the genus of , , , , , , and were screened for oxidative functionalization of oleic acid (). PCM525 was selected as the sole strain catalyzing the one-pot transformation of oleic acid () into natural valuable peach and strawberry-flavored γ-dodecalactone () used in the food, beverage, cosmetics and pharmaceutical industries. Based on the identified products formed during the process of biotransformation, we clearly established a pathway showing that oleic acid () is hydrated to 10-hydroxystearic acid (), then oxidized to 10-ketostearic acid (), giving 4-ketolauric acid () after three cycles of β-oxidation, which is subsequently reduced and cyclized to γ-dodecalactone () (Scheme 1). Moreover, three other strains ( DSM44534, PCM2166, sp. DSM44016), with high concomitant activities of oleate hydratase and alcohol dehydrogenase, were identified as efficient producers of 10-ketostearic acid (), which can be used in lubricant and detergent formulations. Considering the prevalence of γ-dodecalactone () and 10-ketostearic acid () applications and the economic benefits of sustainable management, microbial bioconversion of oleic acid () is an undeniably attractive approach.