The antagonist and synergist potential of cholinium-based deep eutectic solvents

The design of environmentally friendlier solvents has gained increasing relevance in the last decade. Deep eutectic solvents (DES) have recently emerged, with advantages like low-cost and putative lower environmental impact. However, information about DES toxicity is still scarce. This work aims to contribute to profiling the ecotoxicity of DES based on cholinium chloride ([Chol]Cl). Six DES were addressed, combining [Chol]Cl (as hydrogen bond acceptor - HBA) with ethylene glycol, glycerol, 1,2-propanediol, propionic acid, 1-propanol, and urea as hydrogen bond donors (HBD), in different molar ratios. The Microtox® Acute Toxicity Test, was used for assessing their toxicity towards the marine bacteria Allivibrio fischeri . Because the dissociation of DES in water is expected, analysis appraising the mixtures toxicity theory should be considered, which is a step forward in this field. This analysis suggested that [Chol]Cl and all HBD with the exception of propionic acid:[Chol]Cl 1:2 and 4:1 behave antagonistically, which is contrary to what has been suggested previously. The most extreme cases are Urea:[Chol]Cl and 1-Propanol:[Chol]Cl, with EC50 values higher than their starting materials dosed singly, configuring very promising and biocompatible alternative solvents. Toxicity was found to be dependent on DES composition, as well as on molar proportions of the starting materials.publishe

Sequential recovery of C-phycocyanin and chlorophylls from Anabaena cylindrica

Cyanobacteria are attracting the attention worldwide as a reliable and sustainable feedstock for the production of biofuels, food colorants and biochemically active compounds. Anabaena cylindrica (A. cylindrica) is a cya- nobacterium with a significant widespread occurrence in Portuguese freshwaters, with C-phycocyanin and chlorophylls, compounds with a high market value, being abundantly produced by the species. This work presents the development of a sequential downstream process to obtain C-phycocyanin and chlorophyll from A. cylindrica. The C-phycocyanin extraction is carried using Na-phosphate (20 mM, pH 7) buffer, while aqueous solutions of surface-active compounds (250 mM), as well as ethanol, were screened for the extraction of the chlorophylls. After selecting the best solvents to recover both pigments from A. cylindrica, the operational conditions (solid-liquid ratio, time of extraction and temperature) were optimized, allowing the recovery of around 90% and 55% of the total content of C-phycocyanin and chlorophylls, respectively. Finally, dextran/ copolymer-based ABS were applied to promote the purification of C-phycocyanin from the residual chlorophylls and other contaminant proteins, leading to an increase in the C-phycocyanin purity of 4-fold, without com- promising its photostability.publishe