5-Hydroxytryptamine (5-HT), also known as serotonin, is a key neurotransmitter in mood regulation, sleep, and various physiological processes. Imbalances in serotonin levels, especially deficiencies, are associated with depression's pathogenesis, causing persistent sadness and loss of pleasure. Antidepressant medications targeting serotonin have been proven effective, enhancing patients' emotional and mental well-being with fewer side effects than alternatives. Therefore, our project aims to synthetically produce serotonin for depression treatment. By introducing tryptophan hydroxylase 1 (TPH1) through symbiotic bacteria in the patient's gut, we intend to boost serotonin levels. Four TPH1 genes from humans, mice, rabbits, and zebrafish are considered for their comparative functional activities, following Michaelis-Menten kinetics. To ensure safety, we've incorporated an arabinose-inducible suicide system inspired by a prior project, preventing unintended biological contamination or genetically modified organism release.