Conditions for open-air outdoor culture of Dunaliella salina in southern Spain

The optimization of the operation, under the climatic conditions of southern Spain, of an experimental plant for β-carotene production by Dunaliella has been pursued. The effects of mixing, culture depth, cell density and dilution cycles on β-carotene and biomass productivity were studied under a semicontinuous culture regime in open tanks outdoors. Using 3 m2-surface containers, the highest productivity values, for both β-carotene and biomass, were recorded with a flow rate of 0.55 m s−1; 10 cm depth; 0.7 − 0.9 × 106cell ml−1, population density; and dilution cycles of two days. An average annual productivity of 1.65 g (dry wt) m−2 d−1 was estimated for Dunaliella biomass, being that for β-carotene of about 0.1 g m−2 d−1. Under these optimized conditions, experiments have been carried out at the Cadiz Bay with 20 m2-surface tanks during a whole-year cycle. The results obtained have validated this location and the operating conditions established as being most appropriate for efficient mass production of β-carotene rich D. salina.