*Communication* **A Method of Solubilizing and Concentrating Astaxanthin and Other Carotenoids**

**Kiyotaka Y. Hara 1,2,\*,†, Shuwa Yagi 1,†, Yoko Hirono-Hara 2 and Hiroshi Kikukawa 1,2**


**Abstract:** The valuable marine carotenoid, astaxanthin, is used in supplements, medicines and cosmetics. In this study, crustacyanin, an astaxanthin-binding protein, was used to solubilize and concentrate astaxanthin. The recombinant crustacyanin of European lobster spontaneously formed an inclusion body when it was over-expressed in *Escherichia coli*. In this study, fusing the NusA-tag to the crustacyanin subunits made it possible to express in a soluble fraction and solubilize astaxanthin in aqueous solution. By cutting off the NusA-tag, the crustacyanin subunits generated the pure insoluble form, and captured and concentrated astaxanthin. Overall, the attaching and releasing NusA-tag method has the potential to supply solubilized carotenoids in aqueous solution and concentrated carotenoids, respectively.

**Keywords:** astaxanthin; marine carotenoid; crustacyanin; European lobster; NusA-tag; *Escherichia coli*
