en aquaculture aquaculture پژوهشي Orginal research papers In this study, the antibacterial and antioxidant properties of C-phycocyanin (C-PC) from <em>Spirulina platensis</em> were evaluated. The extraction and purification of C-PC were carried out using lyzosyme and ammonium sulphate precipitation, respectively. DPPH radical-scavenging activity, ferric reducing antioxidant power (FRAP) and Fe²⁺-chelating activity were used for evaluation of antioxidant properties of C-PC. Antibacterial activity was also performed using agar well diffusion and microdilution [minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC)]. The selected bacteria were <em>Escherichia coli</em>,<em> Staphylococcus aureus</em>,<em> Listeria monocytogenes</em>,<em> Streptococcus iniae</em> and <em>Yersinia ruckeri</em>. The results showed that the biomass production was 1120 mg L^-1 and C-PC concentration in crude extracts and purified by (NH₄)₂SO₄ were also 1.815 and 3.75 mg ml^-1, respectively. The results of DPPH, FRAP and Fe²⁺-chelating activities of C-PC was 45.75%, 0.051 mg TAE g^-1 and 40.23% at zero time and 41.56%, 0.046 mg TAE g^-1 and 36.56% after 60 days at -18&deg;C, respectively. The results of agar well diffusion indicated that <em>L. monocytogenes</em> and <em>S. </em><em>iniae</em> were the most sensitive and resistant, respectively among examined bacteria in different concentrations of C-PC (0- 25 &micro;g ml^-1) and the mean of inhibition zones were also 7.50-22.11mm. The results of MIC and MBC of C-PC (as &micro;g ml^-1) were 50-500 and 100-500, respectively. As a conclusion, C-PC from <em>S. platensis</em> had high potential of antioxidant activity <em>in vitro</em> and it can be used as natural antioxidants in variety of foods. Antibacterial activity of C-PC was lower than other algal pigments (such as astaxanthin and C-PC in other cyanobacteria). Antibacterial properties, Antioxidant activity, C-phycocyanin, Spirulina platensis 1911 1927 http://jifro.ir/browse.php?a_code=A-10-2328-1&slc_lang=en&sid=1 R. Safari safari1351@gmail.com 100319475328460035695 100319475328460035695 No PhD student Z. Raftani Amiri zramiri@gmail.com 100319475328460035696 100319475328460035696 Yes Associate Professor R. Esmaeilzadeh Kenari reza_kenari@yahoo.com 100319475328460035697 100319475328460035697 No Associate Professor