BETA-CAROTENE Food Grade

b-Carotene is applied as a food coloring additive, as provitamin A in food and feed, in multivitamin products, as an antioxidant, and as a colorant for cosmetics. In the literature, a number of microorganisms are described that are capable of accumulating b-carotene up to relatively high levels, for example, the fungi B. trispora, Phycomyces blakesleanus, the yeast Rhodotorula glutinis, and the above-mentioned alga D. salina. Production processes were developed with mutants of B. trispora in the former Soviet Union (cf. Sect. 2.3) and for D. salina.

Among the b-carotene–producing algae, D. salina is currently the best-known and most efficient producer: D. salina cells are able to synthesize b-carotene in levels a thousand times higher than those of carrots. Dunaliella is also able to synthesize a-carotene, violaxanthin, neoxanthin, zeaxanthin, and lutein. The unicellular green alga D. salina is grown in open ponds without (hardly any) process control. It was shown that the highest production levels were obtained with high light intensities, nitrogen limitation, and stress-inducing temperatures. This has resulted in b-carotene levels up to 12 % of the dry mass. The production facilities are located in places where optimum conditions are found, namely in Australia, Israel, and in the United States; these places benefit from a lot of sunshine, little cloudiness, the availability of saline water, and high average temperatures.