Abstract:

Red yeast Rhodotorula is a common type of marine yeast that is often used as a probiotic in aquaculture. Rhodotorula
mucilaginosa AN5 was isolated from sea ice during the 22nd Chinese Antarctic expedition, and its fermentation conditions
were optimized. The optimal fermentation conditions for AN5 were as follows: 2% molasses, 0.5% yeast powder, 50 mL medium
in 250 mL flask, initial pH=3.0, temperature 20°C, and cultivation for 4 days. Under optimized conditions, the number
of yeast cells can reach 5.81×107 cells·mL⁻¹. Component analysis of AN5 showed that the contents of water, crude protein,
total sugar, and crude fat were 69.15%, 42.00%, 32.08%, and 0.39%, respectively. Juvenile sea cucumbers were fed a diet
containing 0.3 g polar yeast per cubic meter water volume. After two months cultivation, in comparison with the control, the
juvenile test specimens showed no differences in the contents of water and crude fat but significantly increased contents of
protein and total sugar. Consequently, polar red yeast is considered to have potential application as a microecologics in the
culture of sea cucumber.

Key words: Antarctic red yeast, culture optimization, juvenile sea cucumber, microecologics