Selective extraction of intracellular components from the microalga Chlorella vulgaris by combined pulsed electric field-temperature treatment.

The synergistic effect of temperature (25-65 °C) and total specific energy input (0.55-1.11 kWh kgDW(-1)) by pulsed electric field (PEF) on the release of intracellular components from the microalgae Chlorella vulgaris was studied. The combination of PEF with temperatures from 25 to 55 °C resulted in a conductivity increase of 75% as a result of cell membrane permeabilization. In this range of temperatures, 25-39% carbohydrates and 3-5% proteins release occurred and only for carbohydrate release a synergistic effect was observed at 55 °C. Above 55 °C spontaneous cell lysis occurred without PEF. Combined PEF-temperature treatment does not sufficiently disintegrate the algal cells to release both carbohydrates and proteins at yields comparable to the benchmark bead milling (40-45% protein, 48-58% carbohydrates).

Ultrasound-assisted green solvent extraction of high-added value compounds from microalgae Nannochloropsis spp.

The aim of this work was to investigate ultrasound (US)-assisted green solvent extraction of valuable compounds from the microalgae Nannochloropsis spp. Individual green solvents (water, ethanol (EtOH), dimethyl sulfoxide (DMSO)) and binary mixture of solvents (water-DMSO and water-EtOH) were used for the extraction procedures. Maximum total phenolic compounds yield (Yp ≈ 0.33) was obtained after US pre-treatment (W=400 W, 15 min), being almost 5-folds higher compared to that found for the untreated samples and aqueous extraction (Yp ≈ 0.06). The highest yield of total chlorophylls (Yc ≈ 0.043) was obtained after US (W=400 W, 7.5 min), being more than 9-folds higher than those obtained for the untreated samples and aqueous extraction (Yc ≈ 0.004). The recovery efficiency decreased as DMSO>EtOH>H2O. The optimal conditions to recover phenolic compounds and chlorophylls from microalgae were obtained after US pre-treatment (400 W, 5 min), binary mixtures of solvents (water-DMSO and water-EtOH) at 25-30%, and microalgae concentration of 10%.