Engineering Escherichia coli for canthaxanthin and astaxanthin biosynthesis

Area of Science:

• Microbiology
• Metabolic Engineering
• Biotechnology

Background:

• Escherichia coli, a non-carotenogenic bacterium, can be engineered for carotenoid synthesis.
• Carotenoid production necessitates the heterologous expression of specific bacterial genes within E. coli.
• The isoprenoid pathway in E. coli can synthesize the farnesyl pyrophosphate precursor for carotenoids.

Purpose of the Study:

• To describe methods for assembling carotenoid biosynthesis operons in E. coli.
• To evaluate canthaxanthin and astaxanthin production using engineered operons.
• To investigate factors influencing carotenoid yield and purity in E. coli.

Main Methods:

• Assembling carotenoid synthesis operons from diverse bacterial gene clusters.
• Heterologous gene expression in Escherichia coli.
• Incorporating carotenoid modification genes (ketolases, hydroxylases) into operons.

Main Results:

• Operons containing the idi gene achieved over fivefold higher carotenoid titers compared to those lacking it.
• The purity of astaxanthin varied based on the bacterial source of ketolase and hydroxylase genes.
• Gene placement of ketolases and hydroxylases relative to the promoter influenced astaxanthin purity, with proximal expression yielding higher purity.

Conclusions:

• Engineering carotenoid biosynthesis operons in E. coli is feasible using genes from various bacterial sources.
• The idi gene is crucial for enhancing carotenoid titers in engineered E. coli.
• Optimizing the expression and arrangement of modification genes is critical for achieving high purity of specific carotenoids like astaxanthin.