Pilot system for engineering sustainable aquatic food webs: Utilizing cyanobacteria for continuous secretion of ω-polyunsaturated fatty acids

This study introduces a pilot system that uses genetically engineered and marker-less strains of Synechocystis sp. PCC 6803 for enhanced secretion of ω-polyunsaturated fatty acids (ω-PUFAs), specifically intended for aquaculture applications. By inactivating the native acyl-acyl carrier protein synthetase (Aas) and expressing the heterologous Fatty Acid Export 1 (FAX1) gene from Arabidopsis thaliana, transgenic cyanobacterial lines were obtained that continuously secrete PUFAs in the C₁₆ to C₁₈ range. Cellular integrity was maintained in these lines, as evidenced by the monitoring of growth rates and photosynthetic parameters. In a controlled aquaculture set-up with the planktonic crustacean Daphnia magna, using dialysis tubing for spatial separation, the engineered strains significantly enhanced the survival, the proportion of egg-bearing females, and the reproductive output of D. magna. These results underline the potential of genetically engineered algae to act as a sustainable feedstock in aquaculture, enhancing both nutritional quality and environmental safety.