Development of a continuous culture system for stable mass production of the marine rotifer Brachionus

Abstract

In order to improve culture stability, as well as to reduce labor andspace for mass production of the marine rotifer Brachionus, an automaticcontinuous culture system has been developed for practical use. The systemconsists of a filtration unit, a culture unit and a harvest unit. In thissystem, filtered water and food are continuously supplied into a rotiferculture tank at a pre-determined rate, and the same amount of culture wateris transferred into a harvest tank to obtain rotifers at a significantbiomass. B. rotundiformis (so-called S-type) and B. plicatilis (so-calledL-type) were successfully mass-produced from the system, under regulatedconditions of 30 °C (for S-type) or 24°C (for L-type), 20 ppt diluted sea water and totaldarkness. As food for rotifers, commercially available concentrated freshwater Chlorella vulgaris was used. The dilution rate was adjusted to0.6–0.7 d⁻¹ for S-type rotifer and 0.25d⁻¹ for L-type rotifer, respectively. The average productionwas about 2.1 billion rotifers d⁻¹ from a 1-m³S-type continuous culture in which high rotifer densities ranging from 3000to 6000 ind. ml⁻¹ were maintained. On the other hand, about0.17 billion rotifers d⁻¹ on average were obtained from a500-liter L-type culture, with densities ranging from 1100 to 2200 ind.ml⁻¹. The longest duration for a continuous culture was over110 days. Furthermore, experiments utilizing five enrichment techniquesindicate that rotifers from the continuous culture system can easily benutritionally enriched in the same manner as those from common batch culturesystems.