Monday, July 30, 2007 - 1:30 PM
S40
Biomass production of carotenoids by the alga Dunaliella, from the laboratory to mass scale
Ami Ben-Amotz, Marine Phycology, The National Institute of Oceanography, Tel Shikmona, Haifa, 31080, Israel
Dunaliella, halotolerant glycerol and beta-carotene-accumulating alga was treated by mutagen and subsequently by bleaching herbicides to select a sub-species rich with a mixture of 9-cis and all-trans stereoisomers of phytoene and phytofluene, highly scarce colorless carotenoids. The laboratory phytoene/phytofluene-rich Dunaliella was tested outdoors in micro-ponds for a period of a few years to study the acclimation of the algae to high light intensity and to identify the most resistant strains. Prominent bleaching resistant strains were transferred to Eilat, south of Israel, for biomass cultivation in large body open raceways. The phytoene/phytofluene algae were scaled up to a total cultivation pond area of 20,000 m2 using gradual dilution, depth control, inoculation concentration, self shading and chlorophyll per cell ratio. Dunaliella attained successfully high phytoene and phytofluene level of 10 mg/L quite constant over the four annual seasons. The cultures were surprising clean and free of competing halotolerant diatoms and blue-green algae most probably through the highlight intensity bleaching effect and natural selection. Commercial centrifuges were applied to separate the algae to yield concentrated phytoene/phytofluene-rich algal paste. The paste was washed to remove salt and medium contaminant, centrifuged again to concentrated algal slurry and was spray dried to Dunaliella powder containing 4-6% phytoene/phytofluene per dry weight. HPLC analysis revealed that the algal phytoene and phytofluene were maintained non-changed throughout the processing with a stereoisomeric ratio of 9-cis to all-trans of 1:1. Further attempts to produce mass of algae with stereoisomers of other carotenoids will be presented.