The Accumulation of Docosahexaenoic Acid in Rotifers by Feeding the DHA-enriched Yeast, Pichia methanolica HA-32

Abstract

In order to improve the nutritional value of rotifers as the feed for juvenile fish, a yeast, Pichia methanolica HA-32, enriched with docosahexaenoic acid (DHA) was fed to rotifers. The composition of the cultivation medium (pH6) for enrichment of yeast with n-3 highly unsaturated fatty acids were as follows; 5% glucose, 2% yeast extract, 0.5% choline, 1% K2HPO4, 3% free fatty acid rich in DHA. Yeast was incubated at 25°C for 3 d. After incubation, the yeast contained 246 mg of total lipids and 69 mg of DHA per g dry cells. The DHA content in the rotifers cultured with the DHA-enriched yeast reached a maximum after 6 h-feeding. As a result, when 8.0 g (wet basis) of the DHA-enriched yeast (DHA content 170 mg) in 10 L of cultivating water was fed to 800 individuals/mL of rotifers and cultivated for 6 h, 240 mg of total lipids, 51 mg of DHA and 15 mg of EPA in rotifers were recovered. Moreover, the accumulation of DHA in rotifer by feeding the DHA-enriched yeast was more efficient than that by the commercial powdered oil containing the comparable amount of DHA to the DHA-enriched yeast.