Abstract: This invention provides a particulate material suitable for use as a nutritional supplement, particularly as an aquaculture feed. The particulate material has a high proportion of DHA residues in the lipid fraction, which may be up to 35% of the material, or even more. Preferably, the material has a mean particle size of from about 5 microns to about 10 microns. This invention also provides a method for preparing a particulate material suitable for use as an aquaculture feed from microbial biomass, preferably from algal cells having a high content of DHA residues, by obtaining a lipid fraction from the biomass, preferably by solvent extraction of broken cells, followed by separating a fraction containing phospholipids and proteins from the lipid fraction, and removing water from the protein/phospholipid fraction to form a low moisture particulate, preferably by spray-drying the protein/phospholipid fraction.

Abstract: This invention provides a particulate material suitable for use as a nutritional supplement, particularly as an aquaculture feed. The particulate material has a high proportion of DHA residues in the lipid fraction, which may be up to 35% of the material, or even more. Preferably, the material has a mean particle size of from about 5 microns to about 10 microns. This invention also provides a method for preparing a particulate material suitable for use as an aquaculture feed from microbial biomass, preferably from algal cells having a high content of DHA residues, by obtaining a lipid fraction from the biomass, preferably by solvent extraction of broken cells, followed by separating a fraction containing phospholipids and proteins from the lipid fraction, and removing water from the protein/phospholipid fraction to form a low moisture particulate, preferably by spray-drying the protein/phospholipid fraction.

Abstract: This invention provides a particulate material suitable for use as a nutritional supplement, particularly as an aquaculture feed. The particulate material has a high proportion of DHA residues in the lipid fraction, which may be up to 35% of the material, or even more. Preferably, the material has a mean particle size of from about 5 microns to about 10 microns. This invention also provides a method for preparing a particulate material suitable for use as an aquaculture feed from microbial biomass, preferably from algal cells having a high content of DHA residues, by obtaining a lipid fraction from the biomass, preferably by solvent extraction of broken cells, followed by separating a fraction containing phospholipids and proteins from the lipid fraction, and removing water from the protein/phospholipid fraction to form a low moisture particulate, preferably by spray-drying the protein/phospholipid fraction.

Abstract: An apparatus is disclosed for the controlled production of microorganisms by photosynthesis in a closed photobioreactor. The closed photobioreactor contain a photosynthetic culture in a substantially sealed environment and provides a system for recirculating the reactant gas through the culture. This closed loop system can be operated with expensive carbon isotopes (i.e., .sup.13 CO.sub.2 or .sup.14 CO.sub.2). Also, a system is provided for removing the molecular oxygen produced in the photosynthesis reaction from the closed photobioreactor. Furthermore, a pH-regulated control valve is utilized for controlling the addition of reactant gas to the culture in response to the alkalization of the culture.