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

Abstract

Simultaneous production and selective extraction of beta-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 beta-carotene and chlorophyll was determined spectrophotometrically. In addition, beta-carotene contents of the cells growing in the aqueous phase and extracted beta-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 beta-carotene, decreases. However, this decrease is more profound for chlorophyll. Therefore, selective extraction of beta-carotene becomes feasible. Comparison of the total beta-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 beta-carotene production pathway. The beta-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.

Milking microalga Dunaliella salina for β‐carotene production in two‐phase bioreactors

“…salina (CCAP 19/18) was grown in a culture medium containing 1 M NaCl, 10 mM KNO 3 , and 1 mM NaH 2 PO 4 Á2H 2 O (Hejazi et al, 2002). The pH of the medium was adjusted to 7.5 by 3 M HCl.…”

“…h-Carotene and chlorophyll concentrations were determined spectrophotometrically using standard curves (Hejazi et al, 2002). In addition, pigments were detected by high-performance liquid chromatography (HPLC) analysis.…”

“…Organic phases with a log P value of >6 are considered biocompatible for D. salina and can be applied in this process (Hejazi et al, 2002). It was also shown that the extraction rate of h-carotene was a function of the mixing rate of the culture (Hejazi et al, 2003a) and the h-carotene content of the cells (Hejazi et al, 2003b).…”

“…h-Carotene production and extraction were performed in the second bioreactor at higher light intensity (1200 Amol m À2 s À1 ). Dodecane, which is biocompatible for D. salina (Hejazi et al, 2002), was used as organic phase in the second bioreactor (production bioreactor). The bioreactor contained 80% aqueous phase and 20% organic phase.…”

Development of a liquid-liquid extraction method of resveratrol from cell culture media using solubility parameters

“…Liquid-liquid extraction (LLE) is a favorable method to recover bioactive compounds from their culture media with preservation of plant cell viability, especially when both production and extraction occur simultaneously [7]. Many researchers have used a continuous extraction process with an organic solvent directly contacting the aqueous phase, in which the bioconversion is carried out by the plant cells [8].…”