Abstract
Abstract This is the first study of thraustochytrids from the Red Sea coast in Saudi Arabia. One hundred and thirty-four isolates of thraustochytids were cultured from Al-Leith, Jeddah and Yanbu mangroves from this area, and were categorized into 38 morphotypes. Among the isolated thraustochytrids, Aurantiochytrium was the most speciose genus, represented by 36 morphological types. Seventeen strains formed a distinct clade within the genus Aurantiochytrium based on phylogenetic analyses of 18S rDNA sequences. The Aurantiochytrium clade from the Middle East is characterized by the production of high levels of oleic and linoleic acids and may represent undescribed taxa. Four Aurantiochytrium strains were grown on large scale to study their ability to produce docosahexaenoic acid (DHA). These strains produced biomass ranging from 37.7 to 66 g L −1 and the percentages of oil ranged from 40 to 57.2% of the dry weight. Twenty-one fatty acids were recorded from the four strains which included: eight saturated four monounsaturated and nine polyunsaturated. Dominant fatty acids included C16:0 palmitic acid (24.14–37.02% total fatty acid (TFA)), C18:1ω9 oleic acid (3.01–25.07% TFA), C18:2ω6 linoleic acid (1.85–20.85% TFA) and C22:6ω3 DHA (4.87–16.5% TFA). DHA was the predominant polyunsaturated fatty acid in three strains, while linoleic acid was the predominant PUFAs in one strain.