Combined effects of irradiance, temperature and nitrate concentration on phycoerythrin content in the microalga Rhodomonas sp. (Cryptophyceae)

The marine microalga Rhodomonas sp. was studied as a potential resource for the production of phycoerythrin, a red-colored phycobiliprotein which has been used as a fluorescent probe and analytical reagent, as well as a natural dye in food and cosmetics. Influence of temperature, photon flux density, nitrate concentration and light regime on specific growth rate, biomass productivity and phycoerythrin content was investigated. The microalga was batch-cultured in f/2 media at photon flux densities of 15, 50 and 150μmolphotons·m−2·s−1 and temperatures of 20, 26 and 32°C. At each quantum irradiance, increasing temperatures resulted in a decrease in the maximum growth rate. Additionally, the growth rate observed at all temperatures increased with photon flux density from 15 to 50 or to 150μmolphotons·m−2·s−1. Phycoerythrin content was inversely related to photon flux density, whereas pigment content increased with growth temperature from 20 to 26°C. Response surface methodology confirmed that cultivating Rhodomonas at 26°C and 15μmolphotons·m−2·s−1 optimizes phycoerythrin production. In addition, accumulation of biliprotein was stimulated by a 25% increase in nitrate concentration in the culture medium.