Microalgae biomasses: new ingredients for the formulation of high-quality diet in aquaculture

Due to their valuable and balanced biochemical composition, microalgae (including cyanobacteria) are promising candidates as feed ingredients for aquaculture. A deep investigation on quality and safety of microalgae is necessary to increase their exploitation as new ingredients in diet preparation for aquaculture sector. In particular, the nutrient profile and the in vitro digestibility are essential information to provide details about the quality and bioavailability of nutritional constituents of microalgal biomasses. The aim of this study was to investigate the biochemical composition, the dry matter and protein in vitro digestibility of 10 cultivated microalgae and one commercial natural bloom of interest as feed source. Cyanobacteria and most of the freshwater algal species showed higher protein contents (up to 70% in Arthrospira platensis). Marine microalgae showed high amounts of long chain polyunsaturated fatty acids, whereas freshwater species were found to be rich in α-linolenic acid. Cyanobacteria showed the highest digestibility. While, the two green microalgae (Chlorella sorokiniana and Tetraselmis suecica), Nannochloropsis oceanica, Phaeodactylum tricornutum and Porphyridium purpureum showed lower digestibility values. Our study represents the starting point for the selection of the most suitable microalgae for specific feed applications.