Porphyridium spp. is a debated family that produces phycoerythrin (PE) for use in multiple industrial applications. We compared the differences in the biochemical composition and phycoerythrin yield of P. cruentum and P. purpureum by conventional and green extraction technologies. The protein content in P. cruentum was 42.90 ±1.84% w/w. The omega-3 fatty acid (FA) was highlighted by eicosapentaenoic acid (EPA, C20:5, ω-3, ~9.74 ± 0.27% FA) and arachidonic acid (ARA, C20:4, ω-6, ~18.02 ± 0.81% FA) represented the major omega-6 fatty acid. Conversely, P. purpureum demonstrated a higher lipid content (17.34 ± 1.35% w/w) and an FA profile more saturated in palmitic (C16:0, 29.01 ± 0.94% FA) and stearic acids (C18:0, 50.02 ± 1.72% FA). Maceration and freeze/thaw were the conventional methods, whereas microwave (MW) and ultrasound (US) served as green procedures for PE extraction under the factorial-design methodology. Aqueous solvents, extraction-time and power were the main factors in the statistical extraction designs based on Response-Surface Methodology (RSM). Overall, the PE extraction yield was higher (2-to 6-fold) in P. cruentum than in P. purpureum. Moreover, green technologies (US > MW) improved the PE recovery in comparison with the conventional methods for both of the microalgae. The maximum PE yield (33.85 mg/g) was obtained under optimal US conditions (15 min and buffer solvent (PBS)) for P. cruentum. Finally, we proved the biochemical differences between the red microalgae and ratified the advantages of using green extraction for PE because it reduced the processing times and costs and increased the economic and functional-applications of bioactive compounds in the industry.

Cyanobacteria are a rich source of bioactive compounds, mainly in the Arthospira sp., and one of the most interesting components in recent years has been C-phycocyanin (C-PC). There have been several conventional methods for their extraction, among which stand out: chemical products, freezing-thawing (FT); enzymatic, and maceration (M); which have come to be replaced by more environmentally friendly methods, such as those assisted by microwaves (MW) and high-pressure homogenization (HPH). The aim of the research was to use these two “green extraction processes” to obtain C-PC from cyanobacteria Arthrospira maxima because they improve functionality and are fast. Extractions of C-PC were studied by means of two experimental designs for MW and HPH, based on a response surface methodology (RSM) employing, firstly, a factorial design 3³: power (100, 200, and 300 W), time (15, 30, and 60 s), and types of solvents (distiller water, Na-phosphate buffer and, distiller water: Na-phosphate buffer (Ph 7.0; 1:1, v/v); and secondly, two factors with different levels: Pressure (800, 1000, 1200, 1400, and 1600 bar) and, types of solvents (distilled water, Na-phosphate buffer (pH 7.0) 100 mM and, Na-phosphate buffer:water 1:1, (v/v)). Optimum C-PC content was achieved with the HPH process under Na-phosphate solvent at 1400 bar (291.9 ± 6.7 mg/g) and the MW method showed improved results using distilled water as a solvent at 100 W for 30 s (215.0 ± 5.5 mg/g). In the case of conventional methods, the freeze–thawing procedure reached better results than maceration using the buffer (225.6 ± 2.6 mg/g). This last one also did not show a significant difference between solvents (a range of 147.7–162.0 mg/g). Finally, the main advantage of using green extractions are the high C-PC yield achieved, effectively reducing both processing times, costs, and increasing the economic and functional applications of the bioactive compound.

Haematococcus pluvialis is the largest producer of natural astaxanthin in the world. Astaxanthin is a bioactive compound used in food, feed, nutraceutics, and cosmetics. In this study, astaxanthin extraction from H. pluvialis by supercritical fluid extraction was evaluated. The effects of temperature (40 and 50 °C), pressure (40 and 50 MPa), and CO₂ flow rate (2 and 4 L/min) were investigated. The results showed that the highest astaxanthin recovery was obtained at 50 °C/50 MPa and the CO₂ flow rates evaluated had no significant effect. It was possible to achieve astaxanthin recoveries of 95% after 175 min for a CO₂ flow rate of 2 L/min, and 95 min for CO₂ flow rate of 4 L/min. The ω-6/ω-3 ratios obtained were similar in all conditions, reaching 0.87, demonstrating that the extracts from H. pluvialis by SFE are rich in unsaturated fatty acids (UFA) which increases their positive effects when used as a functional ingredient in food.

Haematococcus pluvialis is known to be a natural source of antioxidants for numerous applications. In this study, an oleoresin rich in carotenoids extracted by supercritical CO₂ treatment of H. pluvialis was extensively characterized for its antioxidant capacity. Carotenoid content, fatty acid profile, total phenol content, antioxidant capacity, and viscosity of the oleoresin were determined with the aim of ascertaining the potential of the oleoresin in terms of its antioxidant content for food applications. The oleoresin contained 96.22 mg/g of total astaxanthin (which includes free astaxanthin and astaxanthin esters) and mostly included unsaturated fatty acids (~78% of total fatty acids). High total phenol content and ferric reducing antioxidant potential indicated high antioxidant capacity, but oxygen radical absorbance capacity was lower compared to the oleoresin samples obtained from other species. The oleoresin was a non-Newtonian fluid since it had shear-thinning (pseudoplastic) and shear-thickening (dilatant) flow. Therefore, the H. pluvialis oleoresin is a potential alternative in developing functional ingredients for designing healthy food products. To the best of our knowledge, this is the first study that has reported an extensive characterization of the antioxidant properties of a microalgal oleoresin obtained by means of supercritical CO₂ fluid extraction.