Physical and chemical characteristics of lyophilized biofloc produced into the culture of whiteleg shrimp was determinated. The study consisted in the evaluation of biofloc produced with four experimental diets, isoproteic (35%) and isolipidic (8%), with different fishmeal content: 0 g kg-'(TO), 100 g kg-'(T1), 200 g kg-1 (T2), 300 g kg-1 (T3), and a commercial diet with 300 g kg-1 (TC) as a control. The shrimp was cultured in low salinity (5 g L-1) at a density of 600 ind m-3. The bioflocs were manually collected at day 28, lyophilized, and processed. Proximal composition was determined. To analyze morphology and particle size, photomicrographs were obtained using a Scanning Electron Microscope (SEM). Molecular weights of the protein hydrolysates were determined, and finally the bioflocs protein surface hydrophobicity (S 0) was measured. No significant differences were detected for protein (360-404 g kg-1), lipid (6-8 g kg-1) and fiber (59 g kg-1) contents, but the ashes (205-284 g kg-1) were different. The hydrolysate protein molecular weights were similar, in all cases varied from 22 to 200 kDa. The 50% of lyophilized particles had sizes from 3 to 15 μm. The fluorescence spectra slopes indicated differences in protein surface hydrophobicity (S 0) between the treatments. In general, the physical and chemical characteristics of the bioflocs were independent of the used diet. The lyophilized biofloc has properties that allow its use as a protein source or raw material for biotechnological processes.