The effect of different carbon sources on the nutritional value of bioflocs, a feed for Macrobrachium rosenbergii postlarvae

A 15-day lab-scale experiment was performed to determine the possible use of bioflocs as a feed for Macrobrachium rosenbergii postlarvae. The bioflocs were grown on acetate, glycerol and glucose. A glycerol-fed reactor was initially inoculated with a Bacillus spores mixture. The highest protein content was obtained in the (glycerol+Bacillus) bioflocs, i.e. 58 +/- 9% dry weight (DW). The glycerol and acetate bioflocs showed a lower, but similar content (42-43% DW) and glucose bioflocs contained 28 +/- 3% DW. Higher total n-6 fatty acid contents were observed in the glycerol and (glycerol+Bacillus) bioflocs. The vitamin C content was variable, up to 54 mu g ascorbic acid g-1 DW in the glycerol bioflocs. Bioflocs were fed to M. rosenbergii postlarvae as the sole feed. High survival levels were obtained in the (glycerol+Bacillus) and glucose groups, i.e. 75 +/- 7% and 70 +/- 0% respectively. This was significantly higher than the starvation control (0% survival after 15 days). This indicated that the prawns were able to feed on the bioflocs. These results are in accordance with the biofloc's nutritional parameters and suggest that the choice of the carbon source used for growing bioflocs is of prime importance.