Coordinated Expression of Astaxanthin Biosynthesis Genes for Improved Astaxanthin Production in Escherichia coli

Abstract

Astaxanthin has great potential commercial value in the feed, cosmetics, and nutraceutical industries due to its strong antioxidant capacity. In this study, the Escherichia coli strain CAR026 with completely balanced metabolic flow was selected as the starting strain for the production of astaxanthin. The expression of β-carotene ketolase (CrtW) and β-carotene hydroxylase (CrtZ), which catalyze the conversion of β-carotene to astaxanthin, was coordinated, and a bottleneck was eliminated by increasing the copy number of crtY in CAR026. The resulting strain Ast007 produced 21.36 mg/L and 4.6 mg/g DCW of astaxanthin in shake flasks. In addition, the molecular chaperone genes groES-groEL were regulated to further improve the astaxanthin yield. The best strain Gro-46 produced 26 mg/L astaxanthin with a yield of 6.17 mg/g DCW in shake flasks and 1.18 g/L astaxanthin after 60 h of fermentation under fed-batch conditions. To the best of our knowledge, this is the highest astaxanthin obtained using engineered E. coli to date.

Keywords: Escherichia coli; astaxanthin; coordinated expression; molecular chaperone.