Development of green extraction processes for Nannochloropsis gaditana biomass valorization

Abstract

In the present work, the valorization of Nannochloropsis gaditana biomass is proposed within the concept of biorefinery. To this aim, high-pressure homogenization (HPH) was used to break down the strong cell wall and supercritical fluid extraction (SFE) with pure CO was applied as a first step to extract valuable compounds (such as non-polar lipids and pigments). Extraction of the remaining residue for the recovery of bioactive compounds was studied by means of an experimental design based on response surface methodology (RSM) employing pressurized liquid extraction (PLE) with green solvents such as water and ethanol. Optimum extract was achieved with pure ethanol at 170°C for 20 min, providing an important antioxidant capacity (0.72 ± 0.03 mmol trolox eq g extract). Complete chemical characterization of the optimum extract was carried out by using different chromatographic methods such as reverse-phase high-performance liquid chromatography with diode array detection (RP-HPLC-DAD), normal-phase HPLC with evaporative light scattering detection (NP-HPLC-ELSD) and gas chromatography coupled to mass spectrometry detection (GC-MS); carotenoids (e.g. violaxanthin), chlorophylls and polar lipids were the main compounds observed while palmitoleic, palmitic, myristic acids and the polyunsaturated eicosapentanoic (EPA) acid were the predominant fatty acids in all PLE extracts.

Pressurized Liquid Extraction (PLE) as an Innovative Green Technology for the Effective Enrichment of Galician Algae Extracts with High Quality Fatty Acids and Antimicrobial and Antioxidant Properties

“…Similarly, da Costa Rodriguez research group studied the effect of solvent composition of rice bran oil extracted with ethanol containing different water contents at 60–90 °C and concluded that there were no major differences in the lipid composition present in the extracts [ 42 ]. The use of PLE with green solvents (water and ethanol) for the extraction of bioactives from the microalgae Nannochloropsis gaditana and Phaeodactylum tricornutum was recently investigated [ 43 , 44 ]. Despite the optimum extraction conditions was achieved with pure ethanol, FAs such as palmitoleic, palmitic, myristic acids and EPA were predominant in all PLE extracts from Nannochloropsis gaditana [ 43 ].…”

“…The use of PLE with green solvents (water and ethanol) for the extraction of bioactives from the microalgae Nannochloropsis gaditana and Phaeodactylum tricornutum was recently investigated [ 43 , 44 ]. Despite the optimum extraction conditions was achieved with pure ethanol, FAs such as palmitoleic, palmitic, myristic acids and EPA were predominant in all PLE extracts from Nannochloropsis gaditana [ 43 ]. The PLE of F. vesiculosus algae carried out in this work showed that different solvents produced extracts with different FAs content and therefore, the possibility of using PLE as a selective technique for the extraction of specific carbon number fatty acids.…”

Sub- and supercritical fluid extraction of bioactive compounds from plants, food-by-products, seaweeds and microalgae – An update

“…Thus, non-polar compounds (such as TG) were extracted in the first step whereas mid-polar compounds and polar compounds (almost pigments) were extracted in the following steps. A similar approach was carried out by Sánchez-Camargo et al [132]. In this study, previous high-pressure homogenization (HPH) prior extraction was performed to Nannochloropsis gaditana biomass in order to break or weaken the cell wall and to foster a better extraction of its components.…”

Composition and rheological properties of microalgae suspensions: Impact of ultrasound processing

“…Greater antioxidant capacities than the ones estimated in this work have been described for extracts rich in bioactive components. For instance, antioxidant activities of 100-600 µmol TE/g sample have been described for Scenedesmus obliquus extracts rich in carotenoids [49] and Nannochloropsis gaditana extracts rich in carotenoids, chlorophylls and polar lipids have been reported to possess antioxidant capacities of 300-800 µmol TE/g sample [50]. This indicates that most of the compounds responsible for the high antioxidant potential of microalgae are intracellular components.…”