Fatty acid composition of the L-type rotifer Brachionus plicatilis produced by a continuous culture system under the provision of high density Nannochloropsis

Abstract

Fatty acid profiles of the L-type rotifer Brachionus plicatilis harvested from a continuous culture system were compared respecting the quality of food algae. Nannochloropsis oculata propagated in high density by a panel type photo-bioreactor and fresh water Chlorella suspension on the market were tested. Continuous rotifer culture was carried out under 24°C and 26 psu in a 2000-mL polyethylene bottle. No difference was observed as to the food efficiency when evaluated from the rotifer density and the daily harvesting rate. Both fresh water Chlorella (FC) and the rotifer which fed on the algae (FC-R) had more polar lipid than non-polar one, whereas both Nannochloropsis (N) and the rotifer which fed on the algae (N-R) had more nonpolar lipid than polar one. FC-R were rich in palmitic acid and linoleic acid, and N-R showed high icosapentaenoic acid (IPA) contents, which may reflect the composition in their food algae. A small amount of docosapentaenoic acid (DPA), however, was detected in N-R, although it was not contained in food (N). It is postulated that the rotifers metabolize IPA into DPA at least in the case when cultured with Nannochloropsis.