Heterologous production of novel and rare C30-carotenoids using Planococcus carotenoid biosynthesis genes.

BACKGROUND Members of the genus Planococcus have been revealed to utilize and degrade solvents such as aromatic hydrocarbons and alkanes, and likely to acquire tolerance to solvents. A yellow marine bacterium Planococcus maritimus strain iso-3 was isolated from an intertidal sediment that looked industrially polluted, from the Clyde estuary in the UK. This bacterium was found to produce a yellow acyclic carotenoid with a basic carbon 30 (C30) structure, which was determined to be methyl 5-glucosyl-5,6-dihydro-4,4'-diapolycopenoate. In the present study, we tried to isolate and identify genes involved in carotenoid biosynthesis from this marine bacterium, and to produce novel or rare C30-carotenoids with anti-oxidative activity in Escherichia coli by combinations of the isolated genes. RESULTS A carotenoid biosynthesis gene cluster was found out through sequence analysis of the P. maritimus genomic DNA. This cluster consisted of seven carotenoid biosynthesis candidate genes (orf1-7). Then, we isolated the individual genes and analyzed the functions of these genes by expressing them in E. coli. The results indicated that orf2 and orf1 encoded 4,4'-diapophytoene synthase (CrtM) and 4,4'-diapophytoene desaturase (CrtNa), respectively. Furthermore, orf4 and orf5 were revealed to code for hydroxydiaponeurosporene desaturase (CrtNb) and glucosyltransferase (GT), respectively. By utilizing these carotenoid biosynthesis genes, we produced five intermediate C30-carotenoids. Their structural determination showed that two of them were novel compounds, 5-hydroxy-5,6-dihydro-4,4'-diaponeurosporene and 5-glucosyl-5,6-dihydro-4,4'-diapolycopene, and that one rare carotenoid 5-hydroxy-5,6-dihydro-4,4'-diapolycopene is included there. Moderate singlet oxygen-quenching activities were observed in the five C30-carotenoids including the two novel and one rare compounds. CONCLUSIONS The carotenoid biosynthesis genes from P. maritimus strain iso-3, were isolated and functionally identified. Furthermore, we were able to produce two novel and one rare C30-carotenoids in E. coli, followed by positive evaluations of their singlet oxygen-quenching activities.