Uso de solventes eutéticos profundos na recuperação de lipídeos e carotenóides da microalga dunaliella salina

Abstract

Achieving sustainability in some biotechnological processes still requires overcoming important challenges. In this context, microalgae and Deep Eutectic Solvents (DES) have shown attractive characteristics. Microalgae can biosynthesize products that are used for numerous applications such as pharmaceutical, nutraceutical, cosmetic and recently in the production of biofuels. DESs stand out as adjuvants in stages of cell disruption and biomolecule extraction, working as non-toxic, non-volatile and renewable agents. Seeking to explore techniques for extracting intracellular compounds from microalgae, the aim of this work was to evaluate the cultivation of the microalgae Dunaliella salina in order to maximize the production of lipids and carotenoids, as well as the study of DES-assisted extraction of these compounds. First, microalgae growth was evaluated under three growing conditions: Cultivation under Light Stress (CEL), Cultivation under Nutritional and Light Stress (CENL) and Control Cultivation (CC). The results indicated that the stress caused only by the high light intensity significantly influenced the accumulation of biomass. In the CEL the mean values were 0.46 g.L-1, in the CC 0.37 g.L-1 while in the CENL only 0.25 g.L-1. In turn, the culture conditions did not affect the contents of total lipids and carotenoids, which remained at an average value of 158.42 mg.g-1 and 19.18 mg.g-1, respectively. The CEL culture achieved lipid productivity of 9.78 ± 0.86 mg.g-1.d-1 and carotenoid productivity of 1.24 ± 0.10 mg.g-1.d-1 and was chosen to obtain biomass to carry out the study of extraction using DES as an adjuvant. It was found that the use of different DESs, pure and aqueous based on choline chloride, enhanced the permeability of the Ethanol and Ethyl Acetate (EAE) solvent in the microalgae cell wall. Based on product recovery in crude biomass (without DES pretreatment), the use of DES (Ch-U) increased the recovery of total lipids and carotenoids by 57% and 11%, respectively. The carbohydrate content of dry biomass after treatment with DESs showed losses with mean values of 7.97%. The DES pretreatment achieved a lipid recovery equal to 74.99%, presenting higher values than observed for mechanical pretreatments (sonication-67.34%, ball mill-44.22%). In order to improve the obtainment of carotenoids and reduce the process steps, the extraction from wet biomass using the one-pot method was evaluated. Given these changes, yields of 84.06% ± 1.22 were achieved with DES Ch-U. Finally, the effects of temperature, Ch-U volume and treatment time were investigated by a factorial design. In this experiment, the maximum recovery of the carotenoids (88.91% ± 1.01) was reached after treatment of the wet biomass at 60ºC, by 1.5 mL of DES in just 20 min followed by de addition of EAE in the same pot.