Astaxanthin (3,3'-dihydroxy-4,4'-diketo-β-carotene) (1) is a carotenoid of significant commercial value due to its superior antioxidant potential, application as a component of animal feeds, and ongoing research that links its application to the treatment and prevention of human pathologies. The high commercial cost of 1 is also based upon its complex synthesis. Chemical synthesis has been demonstrated, but produces a mixture of stereoisomers with limited applications. Production from biological sources is limited to natural producers with complex culture requirements. The biosynthetic pathway for 1 is well studied; however, questions remain that prevent optimized production in heterologous systems. Presented is a direct comparison of 12 β-carotene (2) hydroxylases derived from archaea, bacteria, cyanobacteria, and plants. Expression in Escherichia coli enables a comparison of catalytic activity with respect to zeaxanthin (3) and 1 biosynthesis. The most suitable β-carotene hydroxylases were subsequently expressed from an efficient dual expression vector, enabling 1 biosynthesis at levels up to 84% of total carotenoids. This supports efficient 1 biosynthesis by balanced expression of β-carotene ketolase and β-carotene hydroxylase genes. Moreover, our work suggests that the most efficient route for astaxanthin biosynthesis proceeds by hydroxylation of β-carotene to zeaxanthin, followed by ketolation.
[Show abstract][Hide abstract] ABSTRACT: Carotenoids are nutritionally-beneficial organic tetraterpenoid pigments synthesized mainly by plants, bacteria and fungi. Although research has focused on the production of carotenoids in staple crops to improve nutritional welfare in developing countries, there is also an enormous market for carotenoids in the industrialized world, where they are produced both as commodities and luxury goods targeted at the pharmaceutical, nutraceutical, food/feed additive, cosmetics and fine chemicals sectors. Carotenoids are economically valuable because they have diverse bioactive and chemical properties. Some are essential nutrients (e.g. β-carotene), others are antioxidants with specific roles (e.g. lutein and zeaxanthin) or general health-promoting roles that reduce the risk or progression of diseases associated with oxidative stress (e.g. lycopene), and still others are natural pigments (e.g. astaxanthin, which is added to fish feed to impart a desirable pink flesh color). Even carotenoid degradation products, such as damascones and damascenones, are used as fragrances in the perfumes industry. Here we discuss the importance of carotenoids in different market sectors, review current methods for commercial production and its regulation, summarize the most relevant patents and consider evidence supporting the health claims made by different industry sectors, focusing on case studies representing the most commercially valuable carotenoids on the market: β-carotene, lycopene, lutein, zeaxanthin and astaxanthin.
[Show abstract][Hide abstract] ABSTRACT: L. barbarum contains high contents of zeaxanthin, which is produced by conversion of β-carotene into zeaxanthin. β-Carotene hydroxylase catalyzes this reaction. We cloned a cDNA (chyb) encoding β-carotene hydroxylase (Chyb) from L. barbarum leaf. A 939-bp full-length cDNA sequence was determined with 3’-Rapid Amplification of cDNA End (3’-RACE) assay encoding a deduced Chyb protein (34.8 kDa) with a theoretical pI 8.36. Bioinformatics analysis showed that the L. barbarum Chyb located in the chloroplast. Further, to investigate the catalytic activity of L. barbarum Chyb, complementation analysis was conducted in Escherichia coli. The results strongly demonstrated that Chyb chould catalyze β-carotene to produce zeaxanthin. Thus, this study suggests that L. barbarum β-carotene hydroxylase could be a means of zeaxanthin production by genetic manipulation in Escherichia coli.This article is protected by copyright. All rights reserved
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.