Effect of light intensity and nutrient concentration on growth and pigments of the green microalga Tetraselmis suecica

Tetraselmis suecica is a green microalga that thrives under a wide range of conditions, used in the commercial culture of fish, mollusk, and crustacean larvae for supplementing the demand for fertilizers. Its pigments have applications in human health care as drug products, vitamins, and cosmetics. Growth and pigment concentration of T. suecica were evaluated in experimental cultures with different nutrient concentrations and light intensities to determine the most appropriate culture conditions to optimize the production of biomass and pigments. Chlorophyll-a, chlorophyll-b, lutein, violaxanthin, alpha, beta-carotene, and neoxanthin concentrations were evaluated under three different nutrient conditions (441.5/18.1, 883/36.3, and 1766/76.2 mu M of NaNO3/NaH2PO4) and four light intensities (50, 150, 300, and 750 mu mol quanta m(-2) s(-1)). Increases in either or both of these factors lead to increases in the concentration of all pigments. Chlorophyll-a reached up to 5x10(3) mg m(-3), chlorophyll-b up to 2500 mg m(-3), lutein 600 mg m(-3), violaxanthin 300 mg m(-3), alpha, beta-carotene 500 mg m(-3), and neoxanthin 400 mg m(-3). Growth rate (mu) attained values of 1.6 d(-1). An index to evaluate the efficiency of pigment production by light intensity (called LER) was computed. The highest LER was recorded at 50 mu mol quanta m(-2) s(-1) and a nutrient concentration of 1766/76.2 mu M (NaNO3/NaH2PO4); this treatment optimizes pigment production with the lowest light intensity. Our results show that the optimum light intensity should be selected according to the objective of the culture, either maximizing pigment concentration for harvesting at higher concentrations or reducing production costs regarding light consumption.