PRELIMINARY-RESULTS IN IMPROVING ESSENTIAL FATTY-ACIDS ENRICHMENT OF ROTIFER CULTURED IN HIGH-DENSITY

High density cultured marine rotifer (Brachionus rotundiformis) fed on freshwater Chlorella was cultured secondarily with an emulsion of eth yl esters (65% DHA, 15% EPA) for EFA-enrichment, with or without fresh water Chlorella. Culture tanks (301, 201 working volume) set in a wate r bath (24 degrees C) were continuously supplied with air (2.501 m(-1) ) or high-purity oxygen gas (1.251 m(-1)). Samples for fatty acid comp osition analysis were collected at 0, 6, 12, and 24 hours after the in oculation of rotifer, followed by the monitoring of rotifer density, D O, NH4-N and pH. The n-3 HUFA content plateaued at 6 hours after the o nset of the secondary culture and no significant differences were obse rved afterwards, regardless of the aeration methods. The HUFA content increased with decreasing amounts of Chlorella added. The highest cont ent (ca 3.5% on a dry basis) was noted in non-Chlorella feeding groups . When large amounts of Chlorella were fed, the DO of culture water dr astically decreased and the NH4-N concentration increased. The results from the experiment indicate that the presence of Chlorella cells gre atly affect the HUFA intake of rotifers during the secondary culture p rocess. Also the supply of high-purity oxygen gas was effective for pr eventing a culture crash of rotifers during EFA enrichment.