Metabolic Engineering of Escherichia coli for Producing Astaxanthin as the Predominant Carotenoid.

Astaxanthin is a carotenoid of significant commercial value due to its superior antioxidant potential and wide applications in the aquaculture, food, cosmetic and pharmaceutical industries. A higher ratio of astaxanthin to the total carotenoids is required for efficient astaxanthin production. β-Carotene ketolase and hydroxylase play important roles in astaxanthin production. We first compared the conversion efficiency to astaxanthin in several β-carotene ketolases from sp. SD212, sp. DC18, sp. PC1, sp. N81106 and with the recombinant cells that synthesize zeaxanthin due to the presence of the The sp. SD212 and genes are the best combination for astaxanthin production. After balancing the activities of β-carotene ketolase and hydroxylase, an ASTA-1 that carries neither a plasmid nor an antibiotic marker was constructed to produce astaxanthin as the predominant carotenoid (96.6%) with a specific content of 7.4 ± 0.3 mg/g DCW without an addition of inducer.