5. General Culture Procedures
5.5 Mass Culture on Yeast
Baker's yeast has a small particle size (5-7 mm) and a high protein content and is an acceptable diet for Brachionus. The first trials to replace the complete natural rotifer diet by baker's yeast were characterized by varying success and the occurrence of sudden collapses of the cultures (Hirayama, 1987). Most probably the reason for the crashes has to be explained by the poor digestibility of the yeast which requires the presence of bacteria for digestion. Moreover, the yeast needs to be supplemented with essential fatty acids and vitamins to suit the larval requirements of the predator organisms. Commercial boosters, but also home made emulsions (fish oils emulgated with commercial emulgators or with egg yolk lecithin), may be added to the yeast or administered directly to the rotifer tank . Better success was obtained with so called yeast-fed rotifers (rotifers fed on a yeast preparation produced by adding cuttle fish liver oil at a 15% level to the culture medium of baker's yeast) which ensured a high level of (n-3) essential fatty acids in the rotifers (Watanabe et al., 1983). The necessity of adding the component in the food of the rotifer or to the rotifers' culture medium was later confirmed by using microparticulate and emulsified formulations (Watanabe et al., 1983; Léger et al., 1989).
Besides fresh baker’s yeast, instant baker’s yeast, marine yeast (Candida) or caked yeast (Rhodotorula) may also be used.
1.
Introduction
2. Morphology
3. Biology and Life History
4. Strain Differences
5. General Culture Procedures