Microalgal bacterial flocs originating from aquaculture wastewater treatment as diet ingredient for Litopenaeus vannamei (Boone)

Microalgal bacterial flocs (MaB-flocs) in sequencing batch reactors are a novel and promising technology to treat aquaculture wastewater. To improve the economics of this technology, the harvested MaB-flocs should be valorized. Therefore, we investigated if MaB-flocs from an outdoor pilot reactor treating pikeperch (Sander lucioperca L.) wastewater can be used as a colour enhancing ingredient for shrimp diets. Considering the nutritional composition and high ash content of MaB-flocs, five iso-nitrogenous and iso-lipidic shrimp diets were formulated by replacing 2-8% of the basal diet ingredients by MaB-flocs. These diets were continuously fed to juvenile Pacific white shrimps Litopenaeus vannamei (Boone) cultured in a hybrid recirculating aquaculture system. The addition of these relatively low amounts of MaB-flocs to shrimp diets significantly increased the pigmentation (redness and yellowness) of cooked shrimp tails. The diet modifications did not affect the shrimp survival, weight gain, size distribution and food conversion rate, nor did they affect the proximate composition and fatty acid profile of the raw shrimp muscle. This shows that MaB-flocs originating from treatment of pikeperch wastewater can substitute 8% of diet ingredients of Pacific white shrimp while enhancing its pigmentation.