Switchable Solvent Selective Extraction of Hydrophobic Antioxidants from Synechococcus bigranulatus

Abstract

Hydrophobic molecules, in particular, carotenoids, have been directly extracted from Synechococcus bigranulatus ACUF680 by means of secondary amine switchable solvent N-ethylbutylamine (EBA) without any other pretreatment. EBA was able to extract hydrophobic molecules from both fresh and frozen biomass at the same extent of the conventional procedure (about 20% of dry biomass). In particular, selective extraction of a zeaxanthin-enriched fraction (green fraction, GF) and a β-carotene-enriched fraction (orange fraction, OF) was obtained. The ratio between zeaxanthin and β-carotene was 4.4 ± 1.5 for GF, 0.07 ± 0.06 for OF, and about 1 for conventional extraction. These fractions showed in vitro antioxidant activity (IC50 values of 0.056 ± 0.013 and 0.024 ± 0.008 mg mL–1 for GF and OF, respectively) and biocompatibility on immortalized cells. Moreover, OF and GF were able to protect cells from oxidative stress, both before and after thermal treatment. Results clearly indicate that EBA is a good candidate to specifically extract β-carotene and zeaxanthin from the wet biomass of S. bigranulatus without affecting their biological activity. Skipping energy-intensive operations to break the cells and using either fresh or frozen biomass may be the driving factors to use EBA switchable solvent on an industrial scale.

An Alternative Exploitation of Synechocystis sp. PCC6803: A Cascade Approach for the Recovery of High Added-Value Products

“…The IC 50 of 0.09 ± 0.01 mg mL −1 for the extract obtained from the untreated biomass was similar to that obtained on the residual biomass (0.10 ± 0.01 mg mL −1 ). Based on these results, the antioxidant activity was tested on a well-established cell-based system [ 29 ], in which immortalized human keratinocytes (HaCaT) were incubated with the extracts in the presence or absence of UVA, used as a source of oxidative stress. In particular, cells were incubated for 2 h with 80 µg mL −1 of each extract prior to UVA exposure (100 J cm −2 ).…”

“…The biomass was harvested by centrifugation at 1200× g for 30 min at r.t. and resuspended in 50 mM sodium acetate buffer pH 5.5. Cells were disrupted as reported by D’Elia et al [ 29 ] with some modifications. Briefly, cells were disrupted by ultrasonicator (Bandelin SONOPULS HD 3200, tip MS73) for 45 min on ice (30 s on and 30 s off) and the extract was then centrifuged at 5000× g at 4 °C for 30 min.…”

“…At 24 h after seeding, increasing concentrations of crude extract (0.01 to 0.4 mg mL −1 ) or ethanolic extract (from 10 to 200 μg mL −1 ) were added to the cells. After 48h incubation, cell viability was measured by the MTT assay, as described by D’Elia et al [ 29 ]. Cell viability was expressed as the percentage of viable cells in the presence of the extract compared to control cells.…”