Odd-chain polyunsaturated fatty acids in thraustochytrids

► OC-FA C17-C21were detected in two thraustochytrids isolated from Australian waters. ► The essential PUFA; EPA, AA and DHA accounted for 42-44% of the total FA. ► These OC-PUFA were detected at 21.2-27% of the total FA. ► 19:4ω5, 21:4ω5, 21:5ω5 and 21:4ω7 have not been reported in thraustochytrids. ► We propose a pathway from 17:0 and 19:0 leading to the synthesis of the C21 PUFA.