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 beta-carotene production by Dunaliella has been pursued. The effects of mixing, culture depth, cell density and dilution cycles on beta-carotene and biomass productivity were studied under a semicontinuous culture regime in open tanks outdoors. Using 3 m(2)-surface containers, the highest productivity values, for both beta-carotene and biomass, were recorded with a flow rate of 0.55 m s(-1); 10 cm depth; 0.7-0.9x10(6) cell 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 beta-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 m(2)-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 beta-carotene rich D. salina.