Selective extraction of carotenoids from the microalga Dunaliella salina with retention of viability

Abstract

Simultaneous production and selective extraction of β-carotene from living cells of Dunaliella salina in a two-phase system of aqueous and organic phases has been investigated. Solvents with values of log P octanol, which denotes hydrophobicity of a compound, ranging from 3 to 9 were used as organic phase. Viability and activity of Dunaliella salina in the presence of organic solvents were checked by microscopic observation and photosynthetic oxygen-production-rate measurements, respectively. Extraction ability of different solvents for both β-carotene and chlorophyll was determined spectrophotometrically. In addition, β-carotene contents of the cells growing in the aqueous phase and extracted β-carotene by the different organic phases were quantified by the same method. Results showed that solvents having log P octanol > 6 can be considered biocompatible for this alga. Moreover, pigment extraction ability of a solvent is inversely dependent on its log P octanol value. By increasing the degenerative hydrophobicity the extraction ability for both chlorophyll and β-carotene, decreases. However, this decrease is more profound for chlorophyll. Therefore, selective extraction of β-carotene becomes feasible. Comparison of the total β-carotene produced in the presence and in the absence of solvents shows that the presence of a second phase of biocompatible solvents in the culture media may induce the β-carotene production pathway. The β-carotene productivity per cell in a two-phase system with dodecane was the highest observed. Extraction ability of the biocompatible solvents dodecane, tetradecan, and hexadecane was similar. © 2002 Wiley Periodicals, Inc.