Preparation and evaluation of protein microcapsules for a marine suspension-feeder,the Pacific oyster Crassostrea gigas

Little is known of the dietary requirements of marine suspension-feeders, mainly due to difficulties in preparing and delivering microparticulate diets to animals living in an aquatic environment. The food particles must be stable in seawater and digestible by the consumer. A laboratory method for preparing cross-linked, protein-walled capsules is described in this study as a means of delivering dietary protein to marine suspension-feeders such as the oyster Crassostrea gigas. Leakage of ¹⁴C-labelled protein from capsules suspended in seawater for 24 h was reduced to less than 5% by the use of the trifunctional cross-linking agent 1,3,5-benzenetricarbonyl trichloride in wall formation. Invitro experiments indicated that capsules were susceptible to digestion by proteases and by style extracts of oysters. Oysters fed encapsulated ¹⁴C-labelled protein absorbed ¹⁴C with an efficiency of 40.2±5.0% (±1 SE). Biochemical fractionation of capsule-fed oysters indicated breakdown of ingested ¹⁴C-protein into material that was soluble in 7% trichloroacetic acid. Cross-linked, protein-walled capsules can be used successfully to deliver dietary protein to the oyster C. gigas.