Process intensification of ultrasound assisted deep eutectic solvent-based extraction of astaxanthin-rich extract derived from the non-conventional bacterium Paracoccus carotinifaciens

The objective of this work was to develop an integrated ultrasound-assisted deep eutectic solvent-based process for extracting astaxanthin-rich extracts (ARE) from dried biomass of the non-conventional aerobic Gram-negative marine bacterium P. carotinifaciens. Deep eutectic solvents (DES) composed of choline chloride (HBA) and car- boxylic acids/alcohols (HBD) were used as alternative solvents, and the effects of processing intensification parameters on ARE extraction yield were studied. The investigated parameters included extraction temperature, solid/liquid ratio, amplitude level, ultrasound intensity, DES molar ratio, and extraction time. The efficient extraction period for achieving maximum yield of ARE was approximately 8 min, extraction temperature 65 ◦C, solid/liquid ratio 0.05 g/mL, amplitude level: 15 %. Sequential five re-extraction cycles were applied, and it was observed that in two cycles, more than 95 % of total ARE was recovered. The experimental results showed that the choline chloride:acetic acid (CC-C2) DES combined with US enhanced mass transfer, leading to a remarkable recovery yield increase of up to 900 % compared to the conventional procedure. These values were compared with the calculations of the activity coefficient at infinite dilution and the sigma profile delivered by COSMO- SAC, concluding that this tool can be used to predict the behavior of DES for the recovery of ARE.