Astaxanthin formation in the marine photosynthetic bacterium Rhodovulum sulfidophilum expressing crtI, crtY, crtW and crtZ

This study reports the production of astaxanthin in the photosynthetic bacterium Rhodovulum sulfidophilum, which has adequate precursor pools and storage capabilities for heterologous carotenoid production. Chemical mutagenesis was carried out using ethylmethane sulfonate to produce mutants with a modified carotenoid biosynthesis pathway downstream of phytoene. Stable green- and gray-colored mutants were selected. Green mutants contained neurosporene or chloroxanthin as their major carotenoid (>90%), while the gray mutants accumulated phytoene. We previously demonstrated the production of β-carotene in Rhodovulum sulfidophilum by cloning the Erythrobacter longus crtI (phytoene dehydrogenase) and crtY (lycopene cyclase) genes. In the present study, an expression vector for astaxanthin production was constructed that contained the Paracoccus crtW (β-carotene oxygenase) and crtZ (β-carotene hydroxylase) genes in addition to the E. longus crtI and crtY genes. A transconjugant, which can synthesize astaxanthin, was successfully generated (2.0 μg g^-1 DCW).