Conversion of oleic acid to 10‐ketostearic acid by Sphingobacterium sp. strain O22

The conversion of oleic acid by a bacterium, tentatively identified as Sphingobacterium thalpophilum strain O22, was investigated. The microorganism was isolated as a stable culture from compost that was enriched with soybean oil outdoors and subsequently with oleic acid in the laboratory. Strain O22 converted oleic acid to products identified as 10‐ketostearic acid (95% of the total conversion product) and 10‐hydroxystearic acid (5%). This is in contrast to S. thalpophilum strain B‐14797, which produces solely 10‐hydroxystearic acid. Maximal conversion was reached in about 36 h after the addition of oleic acid to the fermentation broth. The yield of 10‐ketostearic acid was approximately 75% from 0.26 g of oleic acid in 30 mL fermentation broth at 28°C and 200 rpm for 48 h. This is the first report on the major production of 10‐ketostearic acid by a microorganism in the genus Sphingobacterium.