Production of the Marine Carotenoid Astaxanthin by Metabolically Engineered Corynebacterium glutamicum

摘要

Astaxanthin, a red C40 carotenoid, is one of the most abundant marine carotenoids. It is currently used as a food and feed additive in a hundred-ton scale and is furthermore an attractive component for pharmaceutical and cosmetic applications with antioxidant activities. Corynebacterium glutamicum , which naturally synthesizes the yellow C50 carotenoid decaprenoxanthin, is an industrially relevant microorganism used in the million-ton amino acid production. In this work, engineering of a genome-reduced C. glutamicum with optimized precursor supply for astaxanthin production is described. This involved expression of heterologous genes encoding for lycopene cyclase CrtY, β-carotene ketolase CrtW, and hydroxylase CrtZ. For balanced expression of crtW and crtZ their translation initiation rates were varied in a systematic approach using different ribosome binding sites, spacing, and translational start codons. Furthermore, β-carotene ketolases and hydroxylases from different marine bacteria were tested with regard to efficient astaxanthin production in C. glutamicum . In shaking flasks, the C. glutamicum strains developed here overproduced astaxanthin with volumetric productivities up to 0.4 mg·L ?1 ·h ?1 which are competitive with current algae-based production. Since C. glutamicum can grow to high cell densities of up to 100 g cell dry weight (CDW)·L ?1 , the recombinant strains developed here are a starting point for astaxanthin production by C. glutamicum .