Bioactive Compounds Production by the Marine Halophilic Dunaliella salina and Its Potential to Control Some Fish Pathogenic Vibrios

Vibrios are waterborne bacteria found in marine coastal waters and brackish environments. They can cause serious infections or gastroenteritis in humans who consume raw or undercooked seafood or shellfish. Consequently, one of the primary research focuses in aquaculture disease management is the inhibition and control of vibriosis. The present study aimed to develop an eco-friendly approach to managing various Vibrio species—including V. anguillarum, V. parahaemolyticus, V. harveyi, V. cholerae, and V. alginolyticus—that pose a threat to aquaculture. To this end, the microalga Dunaliella salina (D. salina) was isolated from a saline lagoon in the El Max District, Alexandria Governorate, and examined for its antibacterial activity against several Vibrio species. A one-factor-at-a-time (OFAT) approach was used to optimize growth conditions in order to maximize both biomass production and antibacterial compound synthesis in D. salina. The results indicated that the optimal concentrations for KNO₃, NaCl, and light intensity after 12 days of incubation were 1.50g/ L, 1.25 M, and 4000 Lux, respectively. Among the solvents tested, the methanol extract exhibited the largest inhibition zones against Vibrio species. GC-MS analysis of the D. salina methanol extract (DSME) identified twenty-two major chemical components. Furthermore, the cytotoxicity and antioxidant activities of DSME were evaluated. Several chemical constituents in DSME are known to have established biological relevance in pharmacology.