Demonstration of continuous supercritical carbon dioxide anti-solvent purification and classification of nano/micro-sized precipitates of algal zeaxanthin from Nannochloropsis oculata

This study examined time dependent continuous supercritical anti-solvent (SAS) recrystallization applied for purifying and generating zeaxanthin rich particulates from micro-algal Nannochloropsis oculata. Feed solutions varied from 0.4 to 1.2 mg/ml subjected into a 250 ml SAS crystallizer to yield a few classifications of nano- or micro-sized purified precipitates corresponding to different recrystallization time zones. The effect of operational conditions on amount, recovery of the zeaxanthin and mean size, morphology of the precipitates was obtained from experimentally designed SAS process. The mean size of particles falls within several hundreds of nanometers and the content of zeaxanthin in the particulates range from 65 to 71%, which relies highly upon the recrystallization time. This work demonstrated an environmental benign process in producing nano- or micro-sized particles containing rich-zeaxanthin from algal solution by using supercritical anti-solvent within minutes.