Abstract
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 Brevundimonas sp. SD212, Sphingomonas sp. DC18, Paracoccus sp. PC1, P. sp. N81106 and Chlamydomonas reinhardtii with the recombinant Escherichia coli cells that synthesize zeaxanthin due to the presence of the Pantoea ananatis crtEBIYZ. The B. sp. SD212 crtW and P. ananatis crtZ genes are the best combination for astaxanthin production. After balancing the activities of β-carotene ketolase and hydroxylase, an E. coli 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.
Highlights
Astaxanthin is a carotenoid of significant commercial value due to its superior antioxidative, anti-inflammatory and anticancer features [1]
It has been demonstrated that astaxanthin biosynthesis proceeds from β-carotene through hydroxylation by CrtZ and ketolation by CrtW [14]
We first compared the catalytic efficiency for ketolating zeaxanthin to astaxanthin by different CrtWs
Summary
Astaxanthin is a carotenoid of significant commercial value due to its superior antioxidative, anti-inflammatory and anticancer features [1]. It has been shown that many bacterial CrtWs and CrtZs are bifunctional, with respect to their substrate [9,10] They can accept β-carotene as well as its hydroxylated or ketolated products as a substrate, resulting in the formation of eight carotenoid intermediates which affect astaxanthin conversion as measured by the percentage. Toratio, increase the astaxanthin ratio, we first compared conversion in efficiency astaxanthin had a higher efficiency astaxanthin production in the literature,reported with recombinant. CrtWs, whichfor had a higher efficiency forreported astaxanthin production in the literature, cells that synthesize zeaxanthin. Balancing the expressions of the two enzymes was carried out with recombinant E. coli cells that synthesize zeaxanthin.
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