BACKGROUND Microalgae have long been adopted for use as human food, animal feed and high-value products. For carotenogenesis, Dunaliella salina is one of the most studied microalgae, yet its protein synthesis has been limitedly reported. In this study, D. salina was cultivated at different NaCl and pH levels to optimize its protein productivity. RESULTS The biomass protein content followed an increase-decrease pattern throughout the growth phases, with a maximum in the exponential phase (60-80% over ash-free dry weight). Adversely, the biomass pigment contents were at relatively stable levels (around 0.5% carotenoids, 1.3% chlorophyll a and 0.5% chlorophyll b over ash-free dry weight). Among the tested conditions (1-3 mol L-1 salinity, pH 7.5-9.5), the highest protein productivity (43.5 mg L-1 day(-1)) was achieved at 2 mol L-1 salinity and pH 7.5 during the exponential phase, which surpassed others by 16-97%. Additionally, table salts were tested to be equivalent and cost-efficient salt sources for the growth medium. CONCLUSION This study highlighted the suitability of D. salina as a protein source, providing guidelines for 70% cheaper medium formulation in the lab and for maximum protein productivity at larger scale. (c) 2018 Society of Chemical Industry