For corynebacterial species lacking some of the crt genes it remains to be shown if and which carotenoids are synthesized. On the other hand, C. michiganense[21], C. erythrogenes[22], C. fascians[23] and C. poinsettiae[24] are known to synthesize carotenoids, but this website their genome sequences are unknown. In this study it could be shown that the genes of the carotenoid gene cluster of C. glutamicum ATCC 13032 crtE-cg0722-crtBIY e Y f Eb are co-transcribed. Similarly, also the second cluster is transciptionally organized as an operon. Transcriptional regulation of both BTK inhibitor mouse operons has not yet been reported. The in vivo activity of the crtB2 gene product appears low due either to

low expression levels or to low catalytic activity as plasmid-borne find more overexpression was required to complement the phenotype of the deletion mutant lacking the paralog crtB. Currently, it remains unknown whether crtB2 expression is affected by environmental stimuli and if/how the function of the two paralogs is regulated. The potential of C. glutamicum for overproduction of carotenoids

is to our knowledge described here for the first time. The interest in production of carotenoids, which find application in a wide variety of products due to their antioxidative properties and their colors, by cost-effective, environmentally friendly microbial fermentation processes is steadily increasing. The carotenogenic C. glutamicum is generally recognized as safe (GRAS), can readily be metabolically engineered and has been safely used in the million-ton-scale production of food-additives since more than 50 years [28]. Lycopene was chosen as a test carotenoid product as it may serve as a platform intermediate and as its red color Cediranib (AZD2171) serves as a simple read out. Lycopene is a commercial product obtained by fermentation with the fungus Blakeslea trispora[29] (Vitatene, Leon, Spain). Here we show that C. glutamicum overproduces lycopene if crtEb is deleted and that additional overexpression of the carotenogenic genes crtE, crtB and crtI boosted lycopene production 80 fold. The achieved lycopene concentration of 2.4 mg/g CDW is already comparable to that obtained

with other popular biotechnological hosts like E. coli, for which e.g. a lycopene yield of 1.8 mg/g CDW was reported when the crtE, crtB and crtI genes of the plant pathogen Pantoea ananatis were overexpressed [20]. A higher lycopene concentration (6.6 mg/g CDW) could only be achieved in an E. coli strain overexpressing genes for IPP synthesis and carotenogenesis after a systematic screen identified three gene knockouts in the central carbon metabolism [30]. In E. coli harboring multiple modifications, i.e. carrying a plasmid with genes of the lycopene biosynthetic pathway (crtE, crtB and crtI) and a plasmid containing the entire heterologous MVA pathway as well as the IPP isomerase gene, idi, and overexpressing the endogenous dxs gene, a lycopene concentration of 6.8 ± 0.4 mg/g was obtained in batch culture [31].