Abstract: A method for processing a separation product, containing carboxylic acids, of a separation process, in particular a process for separating fish oil and/or algae oil, in which method polyunsaturated hydrocarbons are produced at least from some of the carboxylic acids by microbes. Advantageously, the polyunsaturated hydrocarbons are or include omega-3 fatty acids and/or omega-6 fatty acids, preferably EPA, DHA and/or DPA. The microbes are or include yeast, fungus, bacteria and/or in particular marine protists, preferably microalgae. The yeast is preferably a yeast of the Yarrowia lipolytica species and the marine protist is preferably a microalga of the Schizochytrium genus, preferably Schizochytrium limacinum SR21. Biomass is produced from the microbes and includes polyunsaturated hydrocarbons.