Engineering Genome-Reduced Corynebacterium Glutamicum for Isoprenoid Production
Terpenoids are one of the most abundant metabolite classes in nature with over 10000 different structures and exhibit a wide variety of fragrance, flavoring and coloring properties. The yellow-orange-red to violet carotenoids, a subfamily of terpenoids, can be found as pigments in plants, fungi, algae and bacteria. Due to their color and anti-oxidant effects this class of terpenoids becomes more and more attractive to the pharmaceutical and cosmetic industries. The orange-red colored ß-carotene-derived pigment astaxanthin and its precursor zeaxanthin and canthaxanthin are high-value ketocarotenoids with an increasing market. The biotechnologically important bacterium Corynebacterium glutamicum is naturally yellow pigmented due to the synthesis of the C50-carotenoid decaprenoxanthin1. It is used for million ton-scale amino acid production and its biotechnological potential has been widened to include other high-value2. Genome reduction has led to C. glutamicum chassis strains3.
The genomic background of a prophage-cured, genome-reduced C. glutamicum strain MB0014 was engineered for enhanced production of rare carotenoids. Optimization of the supply of the precursor isopenthenyl pyrophosphate (IPP) through chromosomal promoter exchange of dxs, deletion of the endogenous carotenoid genes crtEbY and plasmid encoded expression of homologous genes crtE, crtB and crtI in this C. glutamicum strain led to efficient production of lycopene and the addition of a heterologous crtY gene from Pantoea ananatis resulted in β-carotene production5.
Furthermore, the production of other industrially relevant carotenoids such as canthaxanthin, zeaxanthin and astaxanthin through heterologous gene expression with a two vector system was performed. Variations of crtZ and crtW genes from marine and non-marine bacteria encoding for β-carotene hydroxylases and ketolases, respectively, were compared and with this approach production of canthaxanthin and astaxanthin in the mg/g CDW range was achieved.
1 Heider et al. (2014), Appl Microbiol Biotechnol 98:10, 4355-4368
2 Peters-Wendisch & Wendisch (2014) In: Industrial Biocatalysis. Grunwald (Ed); London: LLC Taylor & Francis: 373–416
3 Unthan et al. (2015) Biotechnol J, 10(2):290-301
4 Baumgart et al. (2013) Appl Environ Microbiol. 79(19):6006-15.
5 Heider et al. (2014), Frontiers in Bioengineering and Biotechnology, doi: 10.3389/fbioe.2014.00028