Enhancement of carotenoid production in Nannochloropsis by phosphate and sulphur limitation

Abstract

Because of its value as antioxidants, food-supplements and in animal-feeding, carotenoids are among the most attractive target compounds of marine microalgae. In this contribution the influence of essential nutrients (N, S and P) limitation on the accumulation of carotenoids in the marine microalga Nannochloropsis gaditana has been studied. High and rapid biomass production, which depends on growth conditions, is the first step in a bioproduction process. In our work was observed that Nannochloropsis gaditana growth was significantly faster when using 5 % (v/v) CO2 in air instead air or HCO3 - as carbon source, at two different pH values assayed (7.2 and 8.2), as revealed from cell chlorophyll content, nitrate consumption rates and light-dependent oxygen production. Afterwards, cells grown to exponential phase were incubated in culture media containing none or limiting concentrations of either nitrate, sulphate or phosphate. The results showed that both starvation and low concentrations of nutrients (0.005 mM P, 0.2 mM N, 1.1 · 10-5 mM S) drove to increases of carotenoids/chlorophyll ratios, specially for sulphur limitation. In a general view, zeaxanthin and violaxanthin content increased in all limiting conditions tested, the increase of violaxanthin content being less pronounced.