Polyunsaturated fatty acids with multiple double bonds, especially docosahexaenoic acid and eicosapentaenoic acid, have attracted global attention due to their beneficial effects on human health. Traustochytrids, or unicellular heterotrophic marine protists, are new sources of omega-3 fatty acids. Polyunsaturated fatty acids with multiple double bonds, especially docosahexaenoic acid and eicosapentaenoic acid, have attracted global attention due to their beneficial effects on human health. These microorganisms play an important role in aquatic ecosystems and show potential applications in biofuel production, food industry, bioremediation, wastewater treatment and various other areas. This study aimed to investigate how different phytohormones affect the growth, physiology and biochemistry of Aurantiochytrium sp. In the present study, the effects of nine different groups of plant hormones, including salicylic acid (SA), gibberellic acid (GA), and jasmonic acid (JA), on the growth and development of Aurantiochytrium sp. were investigated. Various parameters such as optical density, biomass, protein content, hydrogen peroxide and malondialdehyde levels, activity of the antioxidant enzyme catalase at physiological levels, as well as the expression of genes involved in the biosynthesis of fatty acids, including malic enzyme and acetyl-CoA carboxylase, were analyzed at different cultivation times (24, 48, 72, and 96 hours). In addition, the composition of fatty acids, unsaturated fatty acids (UFA), and saturated fatty acids (SFA), as well as the ratio of UFA to SFA, were analyzed. The results showed that changes in the synergistic concentration of phytohormones can lead to changes in the growth, physiology, biochemistry and molecular characteristics of this microalga, although these changes also depend on the growth stage. These findings emphasize the importance of focusing on specific growth stages and fine-tuning the concentration of phytohormones to optimize culture co
