Optimization of microbial cell factories for astaxanthin production: Biosynthesis and regulations, engineering strategies and fermentation optimization strategies.

The global market demand for natural astaxanthin is rapidly increasing owing to its safety, the potential health benefits, and the diverse applications in food and pharmaceutical industries. The major native producers of natural astaxanthin on industrial scale are the alga and the yeast . However, the natural production via these native producers is facing challenges of limited yield and high cost of cultivation and extraction. Alternatively, astaxanthin production via metabolically engineered non-native microbial cell factories such as , and is another promising strategy to overcome these limitations. In this review we summarize the recent scientific and biotechnological progresses on astaxanthin biosynthetic pathways, transcriptional regulations, the interrelation with lipid metabolism, engineering strategies as well as fermentation process control in major native and non-native astaxanthin producers. These progresses illuminate the prospects of producing astaxanthin by microbial cell factories on industrial scale.