Coordinated Expression of Astaxanthin Biosynthesis Genes for Improved Astaxanthin Production in <i>Escherichia coli</i>

Abstract

Astaxanthin has great potential commercial value in the feed, cosmetics, and nutraceutical industries due to its strong antioxidant capacity. In this study, the <i>Escherichia coli</i> 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 <i>crtY</i> 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 <i>groES</i>-<i>groEL</i> 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 <i>E. coli</i> to date.