Long-chain omega-3 unsaturated fatty acids such as eicosapentaenoic acid (EPA) play an important role in human, animal and aquatic health. Microalgae are good sources of unsaturated fatty acids, which have unique pathways for the production of docosahexaenoic acid (DHA) and eicosapentaenoic acid. Isochrysis is one of the sources of microalgae, which has a high level of long-chain unsaturated fatty acids. In the metabolic pathway for the production of long-chain omega-3 and omega-6 unsaturated fatty acids, the enzyme delta 5-desachurase is involved in the conversion of the primary precursors of alpha-linolenic acid and linoleic acid to long-chain omega-3 unsaturated fatty acids. In this study, the microalgae Isochrysis galbana identified the delta 5 desachurase gene, which is responsible for the production of eicosapentaenoic acid and arachidonic acid fatty acids. Therefore, sequential culture was used to purify the microalgae to ensure the absence of bacterial and fungal contamination. The purified microalgae were then identified by sequencing and BLAST of the 18srDNA gene in NCBI, the microalgae Isochrysis galbana. After optimizing the microalgae growth conditions (pH 8, light at 1500 lux and salinity of 35 gr / l), RNA was extracted and cDNA was synthesized. Next, primers designed to identify the delta 5 desachurase gene. They reproduced part of it. Finally, with sequencing of PCR and BLAST products in GenBank, it had 99% similarity and 97% overlap with JQ034610.1 Isochrysis galbana. The acidic nucleic sequence of the cDNA fragment was transformed into an amino acid sequence with the help of CLC Main Workbench 5.5 software. Peptide synthesis was performed with the amino acid sequence of Delta 5 desachurase in other microalgae including Isochrysis galbana (AFD22890.1 and AEA72469.1) and Rebecca salina ABL96295.1 in NCBI using clustal w2. Similarities and differences were observed. The results of the alignment showed three histidine-rich motifs related to the enzyme
