Beyond fatty acids: new insights into bacterial fatty acid derivatives using avocado fermentation as a model system

Despite their relatively week lipolytic activity in comparison to other bacteria and fungi, lactic acid bacteria (LAB) have been already reported to convert fatty acids (FA) into hydroxy or oxo-derivatives with additional functionalities in fermented sausage, fermented milk, cheeses and sourdough. In this study, we investigated the lipid metabolism of three LAB in fermenting two avocado cultivars. Using Liquid Chromatography-High-Resolution Mass Spectrometry, we tracked the fermentation-induced modifications in native lipid profiles. These modifications unveiled an increase in free FA but also the generation of their oxidized derivatives associated with 14 different m/z ratios. A total of 57 species were recognized through the interpretation of tandem mass spectrometry data, corresponding mainly to mono-, di-, and tri-hydroxylated derivatives originating from major unsaturated FA (18:1, 18:2, 18:3), along with oxidized forms of 16:0 and 18:0 FA. Tandem mass spectrometry also suggested oxidized derivatives from minor FA (16:1, 16:2). In certain cases, bacterial-driven hydroxylation processes were confirmed on oleic acid in synthetic media. Overall, bacterial-driven hydroxylation and oxidation enriched avocado with potentially bioactive lipids, offering opportunities for nutraceutical and food applications, with minimal undesirable sensory effects specifically affected by microbial species and avocado cultivar.