Enrichment of Rotifers Brachionus plicatilis with Eicosapentaenoic Acid and Docosahexaenoic Acid Produced by Bacteria

Two bacterial strains, rich in either eicosapentaenoic acid [EPA, 20:5(n-3)] (Shewanella gelidimarina ACAM 456) or docosahexaenoic acid [DHA, 22:6(n-3)] (Colwellia psychroerythrus ACAM 605) were tested for their ability to enrich rotifers Brachionus plicatilis in these polyunsaturated fatty acids. Rotifers were exposed for 24 h to each bacterial strain and to a mixture of the two strains. They were then harvested and their fatty acid compositions were analysed and compared to those of rotifers that had been either starved or fed yeast Saccharomyces cerevisiae or microalgae Terraselmis suecica in 2-L glass flasks. Exposure to 1.4 × 109 cells/mL of the EPA-producing bacterium only resulted in rotifer EPA levels increasing from 0.1% to 1.2% of total dry weight (%dw). Similarly, following exposure to 1.0 × 109 cells/mL of the DHA-producing bacterium only, rotifer DHA levels increased from below detection to 0.1% dw. When exposed to a mixture of the two bacterial strains, containing 7.0 × 108 cells/mL of the EPA producer and 5.0 × 108 cells/mL of the DHA producer, the rotifers' final EPA and DHA levels were 0.5% dw and 0.3% dw respectively. Although feeding strategies need refining, these results show, for the first time, that rotifers can be enriched with DHA from bacteria, and that rotifers can be enriched simultaneously with both DHA and EPA from different bacterial strains.