Microalgae biotechnology for simultaneous water treatment and feed ingredient production in aquaculture br

Abstract

The use of Tetraselmis chui to produce sole feed ingredient and the recovery of nutrients from a recirculating aquaculture system (RAS) aquaculture facility was studied. The microalga was cultured in a pilot-scale (6 m3) outdoor raceway reactor located in a sole production plant. First, the growth of the microalgae, the addition of phosphorus and the quality of the resulting water were studied. It was possible to cultivate in semi-continuous mode T. chui using the purge stream of a RAS, obtaining productivities of 15 mg L1 d1, and reaching 36 mg L1 d1 when phosphorus was added. In terms of water quality of the effluent, the pollutants concentration were below discharge limits (suspended solids and total dissolved nitrogen, phosphorus and carbon) -directive 91/ 271/EEC. In the case of Vibrio sp., the concentration in the culture water at the end of the experiments remained below typical environmental concentrations (<100 CFU mL1). After harvesting, the biomass quality was ana-lysed, being the microalgae produced in semi-continuous using phosphorus-enriched RAS remarkably similar to commercial T. chui. Biomass of T. chui was used in a sole feeding trial to supplement feeds (0, 10 and 20 % inclusion). Adding 10 and 20 % T. chui to the feed reduced the original raw material in fishmeal by 15 and 25 % without altering the gross composition. No significant differences were found in the pre-fattening test of Solea senegalensis in growth and fillet composition using the experimental feed with 20 % of T. chui. Finally, immune activity increased significantly in diets containing >10 % microalgae.