Stability of carotenoids in Scenedesmus almeriensis biomass and extracts under various storage conditions.

Scenedesmus almeriensis biomass is a source of carotenoids, particularly lutein, and is considered to be promising as an alternative source to marigold. One key question concerning alternative sources of lutein is the loss of carotenoids that takes place between harvesting and processing, which in the case of marigold is frequently up to 50%. The work described here involved a study into the stability of the main carotenoids (lutein, violaxanthin, and beta-carotene), as well as other components, under different storage conditions. The experiments were carried out with biomass in three forms: frozen, freeze-dried, and spray-dried. The stability of extracts of Scenedesmus biomass in acetone and olive oil was also studied. The results show that the most important factor in retaining carotenoids is a low temperature. At -18 degrees C the loss of carotenoids was negligible after the storage period, regardless of the biomass form used (frozen, freeze-dried, or spray-dried). On the other hand, the carotenoid content and fatty acid profile was increasingly affected with increasing temperature. However, the protein content is unaffected by storage conditions.

Extraction of carotenoids and chlorophyll from microalgae with supercritical carbon dioxide and ethanol as cosolvent.

The extraction of carotenoids and chlorophylls using carbon dioxide modified with ethanol as a cosolvent is an alternative to solvent extraction because it provides a high-speed extraction process. In the study described here, carotenoid and chlorophyll extraction with supercritical CO(2 )+ ethanol was explored using freeze-dried powders of three microalgae (Nannochloropsis gaditana, Synechococcus sp. and Dunaliella salina) as the raw materials. The operation conditions were as follows: pressures of 200, 300, 400 and 500 bar, temperatures of 40, 50 and 60 degrees C. Analysis of the extracts was performed by measuring the absorbance and by using empirical correlations. The results demonstrate that it is necessary to work at a temperature of 50-60 degrees C and a pressure range of 300-500 bar, depending on the type of microalgae, in order to obtain the highest yield of pigments. The best carotenoid/chlorophyll ratios were obtained by using supercritical fluid extraction + cosolvent instead of using conventional extraction. The higher selectivity of the former process should facilitate the separation and purification of the two extracted pigments.

Supercritical CO2 extraction of beta-carotene from a marine strain of the cyanobacterium Synechococcus species.

Dynamic extraction of carotenoids from a marine strain of Synechococcus sp. (Cyanophyceae) with supercritical CO2 (SC-CO2) was investigated with regard to operation pressure and temperature effects on extraction efficiency. Extraction yield (milligrams of pigment per gram of dry weight) for SC-CO2) was compared with the extraction yield for dimethylformamide (DMF). Carotenoids extracted with SC-CO2 were beta-carotene (Ct), zeaxanthin (Z), beta-cryptoxanthin (Cr), and equinenone; chlorophyll a was poorly extracted, whereas myxoxanthophyll, another major carotenoid, was not extracted under any experimental condition. The highest relative yield, which is defined here as y(r) = [(mg of pigment(SC-CO2)/mg of pigment(DMF))] x 100, was 76.1 +/- 8.6% for Ct, but it rose to 87.0 +/- 3.4% when 15% ethanol was used as cosolvent. The pressure effect on y(r) was found to be significant (p < 0.05) for both Cr and Z, along with total carotenoids, whereas the effect of square T (TT) was significant for only Ct. From empirical correlations, pairwise pressure (bar) and temperature (degrees C), respectively, for optimal extraction were determined to be (358, 50) for Ct, (454, 59) for Cr, and (500, 60) for Z. Cell disruption by sonication or detergent treatment of the biomass did not improve the extraction efficiency. Matrix structure together with material state could explain the low carotenoid extraction yield obtained with SC-CO2 as compared to DMF in Synechococcus sp. However, the process can be applied to selective extraction of different carotenoids.