Natural estolides produced by Pseudomonas sp. 42A2 grown on oleic acid: Production and characterization

Estolides are a group of FA polyesters resulting from ester bond formation between a hydroxyl or olefinic group of one FA and the terminal carboxyl group of a second FA. These products are commonly found in trace amounts, forming tetraglycerides in several oil seed plants, and have been produced by acid clay and enzymatic catalysis in vitro . In this study, natural estolides produced by a bacterial culture are presented for the first time. Pseudomonas sp. 42A2 produced ( E )‐10‐hydroxy‐8‐octadecenoic acid and ( E )‐7,10‐dihydroxy‐8‐octadecenoic acid when grown on oleic acid. It is suggested that these FA were polymerized in culture by a lipase produced by the bacterial strain, resulting in a mixture of estolides. These compounds amounted to 3.8 g/L after 72 h of incubation. LC‐MS analysis indicated that the types of estolides formed were dimers ( m/z 560–610), trimers ( m/z 845–906), tetramers ( m/z 1122–1202), pentamers ( m/z 1328–1424), and hexamers ( m/z 1554–1788), with a relative abundance of 27.5, 19.4, 15, 9.7, and 11%, respectively. This is the first report in which hexamers were detected in a bacterial culture.