The mass culture of Dunaliella viridis (Volvocales, Chlorophyta) for oxygenated carotenoids: laboratory and pilot plant studies

Abstract

The biology, and hence the mass culture, of Dunaliella viridis closely follows that of Dunaliella salina, which is successfully mass cultured for the production of β-carotene. Both algae can grow at extremely high salinities and light intensities. They co-exist in the coastal salt lake, Hutt Lagoon, Western Australia. In contrast to D. salina, D. viridis does not accumulate large amounts of β-carotene, producing only up to 0.7% of mixed carotenoids (lutein, zeaxathin, other oxygenated carotenoids and β-carotene), compared to D. salina’s ca 10% dry wt of mainly β-carotene. However, in laboratory experiments, D. viridis grew much faster and to much higher cell densities than D. salina, and attained levels of mixed carotenoids similar to those of D. salina (ca 13 mg L^-1 carotenoid). Preliminary experiments in outdoor ponds were much less promising. Harvesting by chemical flocculation was as effective as with D. salina, but extraction of carotenoids directly into vegetable oil proved inefficient. When incorporated into feed, caretonoids derived from D. viridis pigmented hen eggs acceptably. Extrapolating from laboratory results, and using costing derived from D. salina technology, the cost of production of mixed oxygenated carotenoids from D. viridis was similar to that for the production of β-carotene from D. salina, at ca $A500 kg^-1.