Ultrasound-Enhanced Subcritical CO₂ Extraction of Lutein from Chlorella pyrenoidosa

Abstract

Lutein is an important pigment of Chlorella pyrenoidosa with many beneficial functions in human health. The main purpose of this study was to extract lutein from C. pyrenoidosa using ultrasound-enhanced subcritical CO2 extraction (USCCE). Effects of operating conditions on the extraction, including extraction pretreatment, temperature, pressure, time, CO2 flow rate, and ultrasonic power, were investigated, and an orthogonal experiment was designed to study the effects of extraction pressure, temperature, cosolvent amount, and time on the extraction yields. The USCCE method was compared with other extraction methods in terms of the yields of lutein and the microstructure of C. pyrenoidosa powder by scanning electron microscopy. A maximal extraction yield of 124.01 mg lutein/100 g crude material was achieved under optimal conditions of extraction temperature at 27 °C, extraction pressure at 21 MPa, cosolvent amount at 1.5 mL/g ethanol, and ultrasound power at 1000 W. Compared to other methods, USCCE could significantly increase the lutein extraction yield at lower extraction temperature and pressure. Furthermore, the kinetic models of USCCE and subcritical CO2 extraction (SCCE) of lutein from C. pyrenoidosa were set as E = 130.64 × (1 - e(-0.6599t)) and E = 101.82 × (1 - e(-0.5683t)), respectively. The differences of parameters in the kinetic models indicate that ultrasound was able to enhance the extraction process of SCCE.

Innovative Alternative Technologies to Extract Carotenoids from Microalgae and Seaweeds

“…Compared to SFE, only a limited number of reports are available describing subcritical fluid extraction of carotenoids from microalgae and seaweeds. Subcritical fluid extraction operates at relatively lower temperature and pressure than SFE [18,23,129,138,139]. In recent studies, subcritical CO 2 , 1,1,1,2-tetrafluoroethane and dimethyl ether (DME) have shown potential to extract carotenoids from microalgae and seaweeds [18,23,129,138,139].…”

“…In this case, the operating pressure is maintained (sometimes higher) to the critical pressure of CO 2 (73.8 bar). Recently, Fan et al [138] reported the extraction of lutein from C. pyrenoidosa using ultrasound-enhanced subcritical CO 2 extraction (UCCE) using ethanol as the co-solvent. The authors achieved excellent recovery of lutein (124 mg/100 g) using USCCE when compared to Soxhlet extraction, subcritical water extraction and supercritical CO 2 extraction.…”

“…In a study Fan et al [138] showed that UAE combined with subcritical CO 2 extraction is an efficient technique for the extraction of lutein from the microalga, Chlorella pyrenoidosa [138]. The combination of UAE and enzyme-assisted extraction for the extraction of lutein was previously described by Deenu et al [156].…”

Modeling of the Kinetics of Supercritical Fluid Extraction of Lipids from Microalgae with Emphasis on Extract Desorption

“…The fatty acid profiles were determined by gas chromatography after methyl esterification of the extract. The details of applied experimental methods are given in the cited literature [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]. …”

“…Models for supercritical fluid extraction were applied on experimental data from microalgae only relatively recently. When the extraction yield plotted against extraction time or solvent-to-feed ratio could be matched by a smooth curve (Figure 1a), either a simple equation of first-order process was applied [12,13,14,15], or more complicated models including mass transfer in the pores of solid particles and in the fluid phase [16] and also the solid-fluid partition coefficient [17] were used. When an abrupt decrease in the extraction rate was visible (Figure 1b), the extraction was assumed to be controlled initially by the solute solubility in scCO 2 and then, after the break of the curve, by internal diffusion [18,19,20].…”