High-level de novo biosynthesis of glycosylated zeaxanthin and astaxanthin in Escherichia coli

Because of wide applications in food, feed, pharmaceutical and cosmetic industries, the carotenoid market is growing rapidly. Most carotenoids are hydrophobic, which limits their bioavailability. Glycosylation is a natural route that substantially increases the water solubility, as well as the bioavailability, photostability and biological activities of carotenoids. Here, we report metabolic engineering efforts (e.g., promoter and RBS engineering, optimization of carbon sources and supplementation of bottleneck genes) to produce glycosylated carotenoids in Escherichia coli. By finetuning the carotenoid-biosynthetic genes (crtX, crtZ and crtY), our strain produced up to 47.2 mg/L (similar to 11,670 ppm) of zeaxanthin glucosides, similar to 78% of the total carotenoids produced. In another construct with mevalonate, astaxanthin pathway and crtX genes, the strain produced a mixture of carotenoid glucosides including astaxanthin and adonixanthin glucosides with a total yield of 8.1 mg/L (1774 ppm). Our work demonstrated a proof-of-concept study for the microbial biosynthesis of glycosylated carotenoids.

Automated summary

The study demonstrated the microbial biosynthesis of glycosylated carotenoids in Escherichia coli through metabolic engineering, significantly improving their water solubility and bioavailability. By fine-tuning the carotenoid-biosynthetic genes, different kinds of carotenoid glucosides were successfully produced.