2026/07/27 by Linda Nedbalová, Milada Vítová, Tomáš Řezanka
paper · doi:10.1111/jpy.70211
Abstract This mini‐review examines odd‐carbon polyunsaturated fatty acids (odd‐PUFAs), a rare but biologically significant group of fatty acids in photosynthetic microorganisms. Odd‐PUFAs are straight‐chain fatty acids containing an odd number of carbon atoms and two or more methylene‐interrupted double bonds. They typically account for less than 1% of total fatty acids in microalgae and cyanobacteria. Current evidence indicates that their biosynthesis primarily originates from propionyl‐CoA‐initiated fatty acid synthesis, followed by conventional elongation and desaturation reactions. The review focuses on three major themes. First, it addresses analytical challenges in odd‐PUFA identification, emphasizing the limitations of gas chromatography with a flame ionization detector (GC‐FID) retention‐time assignments and the need for complementary tandem mass spectrometry (MS/MS)‐based approaches and derivatization techniques for reliable structural characterization. Second, it summarizes the current knowledge of odd‐PUFA biosynthesis, including the metabolic origins of propionyl‐CoA and its incorporation into fatty acid synthase pathways. Third, it surveys the occurrence of odd‐PUFAs across photosynthetic microorganisms, ranging from trace constituents in cyanobacteria and chlorophytes to the characteristic profiles of Euglena gracilis and the very‐long‐chain odd‐PUFAs in dinoflagellates. The primary emphasis is on photosynthetic microorganisms, although thraustochytrids are included as a comparative group because they represent the best characterized microbial system for odd‐chain PUFA biosynthesis. Higher trophic organisms are discussed only briefly to illustrate the transfer of odd‐PUFA algal through aquatic food webs. Advances in lipidomics and the growing interest in odd‐chain fatty acids highlight the need for more research, including analytical standardization, broader taxonomic surveys, and metabolic engineering approaches for biotechnological production.