Dunaliella accumulates massive amounts of flcarotene when cultivated under high light intensi~ and growth-limiting conditions. The pathway for biosynthesis of fl-carotene was elucidated by analysis of the effect of selected inhibitors. The presence oJ the inhibitors elicited the accumulation of the following intermediates: fl-zeacarotene, lycopene, ~-carotene, phytofluene, phytoene and a few unidentified long-chain isoprenoids. Each of the accumulated intermediates was composed of about equal amounts of two stereoisomers, as is the case for fl-carotene in the untreated algae. It is deduced, therefore, that the isomerization reaction occurs early in the pathway of fl-carotene biosynthesis, at or bejore phytoene.
The tmique carotenogenesis properties of Dunaliella led to the development of a new biotechnological process for mass-cultivation of the alga. ('ommercial production facilities for flcarotene rich Dunaliella exist today in Israel, USA, Australia, Spain and China. Recent developments, which indicate that the stereoisomeric mixture of fi-carotene present in Dunaliella is preferentially absorbed in animal tissues, coupled with new evidence for the efficacy of fl-carotene in reducing the ittcidence of cancer, have opened new vistas of potential markets for the high fl-carotene algae.