To produce a new carotenoid sulfate, soluble in a water-soluble solvent and useful as a color tone improving agent and a redyeing agent for cultured fishes and shellfishes, a food additive, etc., by culturing a microorganism of the genus Flavobacterium having the productivity of a new carotenoid sulfate.

This new carotenoid sulfate is represented by formula I (M1 is H or a monovalent metal) and formula II (M2 is H or a monovalent metal) and is useful as a color tone improving agent and a redyeing agent for fishes and shellfishes, a food additive, etc., soluble in a water-soluble solvent. The new highly polar carotenoid is obtained by inoculating a microorganism, belonging to the genus Flavobacterium and having the ability to produce the new carotenoid sulfate [e.g. Flavobacterium PC-6 strain (FERM P-15183)] into a culture medium, separating the microbial cell from the cultured solution, extracting and purifying the resultant product as nostoxanthin-3-sulfate represented by formula I and 4-ketonostoxanthin-3'-sulfate represented by formula II.