Supercritical Fluid Extraction of Fucoxanthin from the Diatom Phaeodactylum tricornutum and Biogas Production through Anaerobic Digestion

Abstract

Phaeodactylum tricornutum is the marine diatom best known for high-value compounds that are useful in aquaculture and food area. In this study, fucoxanthin was first extracted from the diatom using supercritical fluid extraction (SFE) and then using the extracted diatom-like substrate to produce bioenergy through anaerobic digestion (AD) processes. Factors such as temperature (30 °C and 50 °C), pressure (20, 30, and 40 MPa), and ethanol (co-solvent concentration from 10% to 50% v/v) were optimized for improving the yield, purity, and recovery of fucoxanthin extracted using SFE. The highest yield (24.41% w/w) was obtained at 30 MPa, 30 °C, and 30% ethanol but the highest fucoxanthin purity and recovery (85.03mg/g extract and 66.60% w/w, respectively) were obtained at 30 MPa, 30 °C, and 40%ethanol. Furthermore, ethanol as a factor had the most significant effect on the overall process of SFE. Subsequently, P.tricornutum biomass and SFE-extracted diatom were used as substrates for biogas production through AD. The effect of fucoxanthin was studied on the yield of AD, which resulted in 77.15 ± 3.85 LSTP CH4/kg volatile solids (VS) and 56.66 ± 1.90 LSTP CH4/kg VS for the whole diatom and the extracted P.tricornutum, respectively. Therefore, P.tricornutuman can be considered a potential source of fucoxanthin and methane and both productions will contribute to the sustainability of the algae-biorefinery processes.

Fucoxanthin from Algae to Human, an Extraordinary Bioresource: Insights and Advances in up and Downstream Processes

“…They provide rapid and efficient extraction which can preserve pigments without structure modification due to prolonged contact at high temperature. Subcritical and supercritical fluids have also been considered as they have high recovery in fucoxanthin and are more environment-friendly due to less consumed amount of organic solvents, easy to be removed and the use of non-toxic supercritical carbon dioxide but they present lower selectivity among the pigments and higher operation cost as main drawbacks [199,202,203,212]. Electrotechnologies-assisted methods, such as pulsed electric field [213,214], moderate electric field [215], high-voltage electric discharges [216] and electropermeabilization-assisted liquid biphasic flotation [217], provide a good extraction of intracellular components by delivering electric current and allowing an electroporation which increases solvent permeability and hence increases pigment extraction efficiency [218].…”

High-Purity Fucoxanthin Can Be Efficiently Prepared from Isochrysis zhangjiangensis by Ethanol-Based Green Method Coupled with Octadecylsilyl (ODS) Column Chromatography

“…The exploitation of the separation of FX from I. zhangjiangensis using a green chemistry strategy is still facing numerous challenges, which has become the main scientific-technological barrier to the high-value utilization of the microalga. The FX production yield from microalgae depends on the microalgal species, biochemical characterization of algal biomass (including carotenoid and chlorophyll profiles), cell wall nature, and the extraction’s experimental conditions [ 22 ]. For example, an efficient method of FX purification from P. tricornutum has been developed, using two-step ethanol precipitation under a vacuum evaporation process [ 23 ].…”

“…Notably, P. tricornutum is an excellent source of FX owing to (all- E )-FX being the predominant carotenoid therein [ 20 ]. Tremendous progress has been achieved in developing methods for downstream fucoxanthin preparation from P. tricornutum [ 21 , 22 , 23 ].…”