Nanoencapsulation of carotenoid extract via the temperature-induced phase transition of triblock polymer in Supercritical Carbon dioxide (scCO2)

Objectives: Carotenoids are increasingly explored as nutraceuticals but their low bioavailability due to poor aqueous solubility limits their applications. This study discusses the development of a novel and organic solvent-free method to develop carotenoid-containing polymeric nanoparticles via temperature-induced phase transition (TIPT) of pluronic F-68 to obtain formulations with the improved dissolution of carotenoids. Methods: The nanoencapsulation of carotenoids in pluronic F-68 was performed in supercritical carbon dioxide (scCO2) to avoid oxidative or temperature/solvent-induced degradation. The nanoencapsulates were prepared in scCO2 at 40 or 60 °C and 10 MPa without the aid of any organic solvent. The formulations thereafter were characterised for particle size via dynamic light scattering (DLS), particle morphology via Scanning Electron Microscopy (SEM) and carotenoid content/release via high-performance liquid chromatography (HPLC). Key findings: HPLC results showed carotenoid degradation to be negligible in freshly prepared formulations when prepared in scCO2 at 60 °C and 10 MPa. The developed particles were spheroidal with sizes ranging between 150-250 nm depending on carotenoid content in the preparation. An improvement in the aqueous solubility and storage stability (5 ºC) of carotenoids was also observed for the formulations prepared in scCO2. Conclusions: These results suggest that TIPT under scCO2 can be applied to formulate nanoparticulates with improved dissolution rate and stability of thermosensitive molecules such as carotenoids without causing any degradation during the processing

Potential of new isolates of Dunaliella Salina for natural β-Carotene production

The halotolerant microalga Dunaliella salina has been widely studied for natural β-carotene production. This work shows biochemical characterization of three newly isolated Dunaliella salina strains, DF15, DF17, and DF40, compared with D. salina CCAP 19/30 and D. salina UTEX 2538 (also known as D. bardawil). Although all three new strains have been genetically characterized as Dunaliella salina strains, their ability to accumulate carotenoids and their capacity for photoprotection against high light stress are different. DF15 and UTEX 2538 reveal great potential for producing a large amount of β-carotene and maintained a high rate of photosynthesis under light of high intensity; however, DF17, DF40, and CCAP 19/30 showed increasing photoinhibition with increasing light intensity, and reduced contents of carotenoids, in particular β-carotene, suggesting that the capacity of photoprotection is dependent on the cellular content of carotenoids, in particular β-carotene. Strong positive correlations were found between the cellular content of all-trans β-carotene, 9-cis β-carotene, all-trans α-carotene and zeaxanthin but not lutein in the D. salina strains. Lutein was strongly correlated with respiration in photosynthetic cells and strongly related to photosynthesis, chlorophyll and respiration, suggesting an important and not hitherto identified role for lutein in coordinated control of the cellular functions of photosynthesis and respiration in response to changes in light conditions, which is broadly conserved in Dunaliella strains. Statistical analysis based on biochemical data revealed a different grouping strategy from the genetic classification of the strains. The significance of these data for strain selection for commercial carotenoid production is discussed

High light responses by isolates of Dunaliella reveals their potential for hyper-accumulation of carotenoids

The halotolerant microalgae Dunaliella salina and Dunaliella bardawil have been widely studied for natural β-carotene production. This work shows biochemical characterization of three newly isolated Dunaliella strains DF15, DF17 and DF40 compared with D. salina CCAP 19/30 and D. bardawil UTEX 2538. All strains exhibited photoprotection capacity and maintained a high rate of photosynthesis under high light stress, and all strains showed an overall increase in cellular content of carotenoids in response to increased light intensity. A major difference among the strains was their ability to accumulate high contents of individual carotenoids under high light stress. DF15 and UTEX 2538 accumulated more carotenoids, β-carotene in particular, than the other strains. DF15 but not UTEX 2538 accumulated a large amount of β-carotene under low light intensity. For all strains strong positive correlations were found between pairs of all-trans β-carotene, 9-cis β-carotene, all-trans α-carotene, zeaxanthin and total carotenoids. Lutein, however, was more closely correlated with dark respiration, photosynthesis and chlorophyll. Lutein has so far only been reported in association with photosynthesis in plants. Overall our data indicate that Dunaliella strains have coordinated universal photoprotection mechanisms for the maintenance of high photosynthetic efficiency under high light stress. The significance of these data for strain selection for commercial carotenoid production is discussed