Evaluation and screening of efficient promoters to improve astaxanthin production in Xanthophyllomyces dendrorhous.

Astaxanthin is a valuable carotenoid that is widely used in the aquaculture, food, pharmaceutical, and cosmetic industries. Xanthophyllomyces dendrorhous is a carotenoid-synthesizing yeast strain that produces astaxanthin as its main pigment. Although metabolic engineering using gene manipulation is a valuable way to improve astaxanthin production, a gene expression system for X. dendrorhous has been poorly developed. In this study, three known promoters of X. dendrorhous, glycerol-3-phosphate dehydrogenase (gpd) promoter (Pgpd), glucose dehydrogenase (gdh) promoter (Pgdh), and actin (act) promoter (Pact), were evaluated for use in the overexpression of target proteins using green fluorescence protein (GFP) as an expression level indicator protein. The actin promoter, Pact, showed the highest expression level of GFP when compared with Pgpd and Pgdh. Additionally, to obtain new promoters for higher expression of target protein in X. dendrorhous, intracellular GFP intensity was evaluated for 13 candidate promoters. An alcohol dehydrogenase promoter, Padh4, showed more efficient expression of GFP rather than Pact. Overexpression of crtE gene encoding rate-limiting enzyme of carotenoid synthesis under the adh4 promoter yielded an increase in intracellular astaxanthin content of about 1.7-fold compared with the control strain. The promoters identified in this study must be useful for improving carotenoids production in X. dendrorhous.