Direct extraction of astaxanthin from the microalgae Haematococcus pluvialis using liquid-liquid chromatography

The microalgae Haematococcus pluvialis (H. pluvialis) is used for biotechnological production of the red carotenoid astaxanthin. Astaxanthin synthesis involves the formation of a rigid cell wall that impedes direct astaxanthin extraction into a solvent. During the subsequent downstream processing, the algal broth is harvested by centrifugation, dried and mechanically disrupted; finally, astaxanthin is extracted with supercritical CO₂. In this study, an alternative extraction process was established, using a liquid-liquid chromatographic column to directly extract astaxanthin from the fermentation broth into a solvent. To achieve this, germination of H. pluvialis cyst cells was initiated, resulting in the release of flagellated zoospores into the fermentation broth. It was shown that astaxanthin could be extracted from the zoospores directly from the algal broth using different solvents; with ethyl acetate, yields reaching 85% were achieved in a shake-flask extraction. Using a liquid-liquid chromatographic column, astaxanthin concentrations reaching 500 mg L^-1 were obtained, corresponding to eightfold concentration of the astaxanthin content in the fermentation broth. The mechanical cell disruption, drying and extraction with supercritical CO₂ in the conventional astaxanthin production can be replaced by a direct astaxanthin extraction process, using a liquid-liquid chromatographic column. This allows direct astaxanthin extraction at the site of H. pluvialis production.