Nannochloropsis (Eustigmatophyceae) as source of commercially valuable pigments

Abstract

Pigment composition and its variation with culture age were analyzed in six strains of Nannochloropsis (Eustigmatophyceae). The capacity for accumulation of the ketocarotenoids astaxanthin and canthaxanthin was higher in N. salina and N. gaditana than in the other strains studied here. The influence of salinity (15 to 100 practical units) on pigment production was studied in N. gaditana, where a defined pattern of variation could not be found apart from a notable increase in zeaxanthin at 100‰. In cultures grown in a photobioreactor and at high cell densities of about 109 cells mL-1, pigment production reached: 350 mg L-1 for chlorophyll a, 50 mg L-1 for violaxanthin, 5 mg L-1 for canthaxanthin, 3 mg L-1 for astaxanthin. The highest contents of canthaxanthin and astaxanthin obtained in experiments with N. gaditana were 19.4 and 14.6 ng pigment (106 cells)-1, respectively, which accounts for 0.7% dry weight. By means of xanthophyll cycle induction through exposure of cells to high irradiance and at 40 °C, conversion of violaxanthin into zeaxanthin may attain up to 70% of the violaxanthin content, which corresponds to 0.6% dry weight. The results indicate that interest in Nannochloropsis as a source of valuable pigments is not related to its capacity for single pigment accumulation, but the availability of a range of pigments such as chlorophyll a, zeaxanthin, canthaxanthin and astaxanthin, each with high production levels.