Room-Temperature Cell Disruption and Astaxanthin Recovery from Haematococcus lacustris Cysts Using Ultrathin α-Quartz Nanoplates and Ionic Liquids

Abstract

Ionic liquids (ILs) are new green solvents, which are widely used in lignocellulosic and microalgal biorefineries. However, high-temperature operating conditions limit their application in the extraction of heat-labile algal products, such as bioactive astaxanthin. In this study, we report the technical feasibility of room-temperature astaxanthin extraction from Haematococcus lacustris cysts with a thick and complex cell wall structure, by combining ultrathin α-quartz nanoplates (NPLs) with ethyl-3-methylimidazolium ([Emim])-based ILs. When four different [Emim]-based ILs with thiocyanate (SCN), diethylphosphate (DEP), HSO4, and Cl anions were applied to 90-day-old H. lacustris cysts at room temperature (~28 °C), the astaxanthin extraction efficiency was as low as 9.6-14.2%. Under sonication, α-quartz NPLs disrupted the cyst cell wall for a short duration (5 min). The astaxanthin extraction efficacies of a subsequent IL treatment improved significantly to 49.8% for [Emim] SCN, 60.0% for [Emim] DEP, 80.7% for [Emim] HSO4, and 74.3% for [Emim] Cl ions, which were 4.4, 6.1, 8.4, and 5.2 times higher than the extraction efficacy of only ILs, respectively. This finding suggests that α-quartz NPLs can serve as powerful cell-wall-disrupting agents for the room-temperature IL-mediated extraction of astaxanthin from robust algal cyst cells.

Preparation of Two-Dimensional Fe3O4 Nanodisks and Nanosheets Transformed from α-Fe2O3 Analogues and Their Applications in Magnetic Field-Assisted Microalgal Harvesting Biorefinery Processes

“…Also, the EEs of Fe 3 O 4 NDs and NSs exhibited a monotonous rise as the ND and NS concentrations were increased until they reached a plateau saturated at concentrations greater than >∼700 mg/L (Figure S14). In addition, the dosage of Fe 3 O 4 NSs required for the ATX EE of ∼35% was ∼300 mg/L, which is significantly lower than ∼800 mg/L of α-quartz nanoplates of similar LSs and TNs used in extraction controls. , These results verify the hypothesis that higher concentrations of anisotropic Fe 3 O 4 NDs and NSs lead to higher EEs. This may be attributed to more frequent collisional interactions between NDs or NSs and H.…”

“…pluvialis cysts was substantially improved by repeated cycles of Fe 3 O 4 NS-assisted cell wall disruption, followed by extraction from the biphasic separation. The results of this study suggest that the ATX EEs from the double extraction processes used by Fe 3 O 4 NSs are either comparable or marginally better than those by α-quartz nanoplates based on a comparison with those of the previous work. , Furthermore, Figure S15 shows optical microscopy images of mature cyst cells treated with Fe 3 O 4 NSs before and after the extraction of red-ATX-containing lipid droplets without major morphological changes such as cellular shrinkage or deformation. These results are comparable to those of α-quartz nanoplates having dimensions commensurate with those of Fe 3 O 4 NSs …”

“…pluvialis solution of 700 mg cell/L was prepared using freeze-dried H. pluvialis and purified Milli-Q water under ambient conditions. ,, The solution was then mixed vigorously (Vortex 3, IKA, Germany), and 6 mL aliquots were dispensed into 11 mL Pyrex-glass tubes with a Teflon-sealed screw stopper. Fe 3 O 4 NDs and NSs (a gray-black powder) were added to the tubes to a concentration of 100–700 mg/L and vortexed briefly for 5 s. The resulting solutions were treated for 5 min in an ultrasonic bath (2510-DTH, Branson, USA; 40 kHz, 100 W) to provide sufficient physical contact between Fe 3 O 4 NDs and NSs and algal cells during ultrasonication.…”

“…An algal solution of 700 mg cell/L, considered typical for H. pluvialis cell concentrations, was prepared using freeze-dried H. pluvialis and purified Milli-Q water under ambient conditions. 33,34,42 The solution was then mixed vigorously (Vortex 3, IKA, Germany). Subsequently, 6 mL aliquots were dispensed into 11 mL Pyrex-glass tubes with a Teflon-sealed screw stopper.…”

Astaxanthin as a King of Ketocarotenoids: Structure, Synthesis, Accumulation, Bioavailability and Antioxidant Properties

“…Studies have also shown that nanotechnology employing nanoparticles and laser light irradiation can electroporate the cell wall of Haematococcus . It has been observed that α-quartz nanoplates (NPLs) in combination with an ethyl-3-methylimidazolium (Emim) ionic liquid helps in extracting astaxanthin from Haematococcus at room temperature [ 104 ]. It was observed that extraction by ionic liquid alone was much less effective than the combination of ionic liquid and α-quartz NPLs.…”