Direct Extraction of Astaxanthin from H. pluvialis

The carotenoid astaxanthin is valued in the cosmetics and dietary supplement industry for its antioxidantproperties and its reddish-purple color, which is used for coloring different food types, e.g. seafood. The highest concentration occurs in the microalgae Haematococcus pluvialis(H. pluvialis), but astaxanthin can also be chemically synthesized. The last years have shown a growing consumer demand for the natural form. However, the industrial extraction from H. pluvialisharbors many disadvantages resulting in high production costs. H. pluvialis produces astaxanthin upon nitrate deprival and exposure to high light intensity during which a thick cell walldevelops. This impedes direct extraction, which is only enabled via a complex multi-step downstream process involving centrifugation, mechanical cell-wall disruption, drying, and supercritical extraction using CO₂. However, harvesting H. pluvialis via centrifugation can account for up to 30% of total production costs. Cell-wall disruption and drying are both energy-intensesteps, and drying at high temperatures holds the considerable risk of degradation. In addition, for supercritical CO₂ extraction pressures of up to 1,000 bar are required to achieve sufficient yields. The energy and cost-intense conventional downstream process therefore represents the bottleneck for producing adequate amounts of natural astaxanthin at an economically favorable scale.

We describe a novel downstream process for direct natural astaxanthin extraction from H. pluvialis. This method replaces the conventional energy- and cost-intensive industrial process steps of spray drying and CO₂extraction and presents an alternative to mechanical cell disruption. By using a centrifugal partition extractor (CPE), astaxanthin is directly extracted from the algal broth into ethyl acetate, a green solvent. To make astaxanthin accessible to the solvent, the cyst cells must either be germinated before the extraction or mechanically disrupted (homogenized). Germination takes places after exposure to growth conditions. The released zoospores contain astaxanthin with a thin cell membrane. This allows the direct extraction into ethyl acetate using the CPE. After evaporating the solvent, a pure astaxanthinextract is obtained which allows he condensed solvent to be recycled and reused for the following CPE extraction round.

• Increased consumer demand of natural axastanthin can be met
• Replacement of spray drying and CO₂extraction with direct extraction via CPE
• Lower investment costs for CPE extractor compared to in-house CO₂ extractor
• Highest net present value for extraction from germinated zoospores and homogenized cyst cells

Proof of concept