Carotenoids are pigmented compounds produced by plants and microorganisms. Particularly interesting for its utility is β-carotene, which has health benefits for humans. β-carotene is also used in the food and pharmaceutical industry. Majority of β-carotene is produced by chemical synthesis. Production of β-carotene by expression of the target genes in heterologous host microorganisms is an interesting alternative to a chemical synthesis. In this thesis we used the bacteria Streptomyces rimosus as the host organism for heterologous expression of crt gene cluster encoding biosynthesis of isorenieratene. To further increase the titer of target carotenoids, we also co-expressed mevalonate pathway mevc encoding the biosynthesis of building isopentenyl pyrophosphate and dimethylallyl pyrophosphate. It seems, that, the biosynthetic gene cluster for isorenieratene is poorly expressed during applied growth conditions. We employed plasmid constructs harbouring various crt gene cassettes (crtE, crtI, crtB, crtY, crtV and crtU), encoding isorenieratene and mevalonate pathways. These constructs were introduced into S. rimosus strains ATCC 10970 ∆145 ∆OTC and S. rimosus ATCC 10970 via conjugation. The selected transformants were firstly cultured in vegetative GOTC medium and then the culture was transferred to production SM medium. During the experimental work, the carotenoids extraction procedure was optimized. By applying LC-MS/MS method, we identified β-carotene, and presence of the isorenieratene. We demonstrated that S. rimosus ATCC 10970 ∆145 ∆OTC strain and S. rimosus ATCC 10970 strain, containing crt genes are capable of synthesizing β-carotene. We demonstrated, that the S. rimosus ATCC 10970 strain generated higher titers of β-carotene, compared to S. rimosus ATCC 10970 ∆145 ∆OTC strain.
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