Microbial Astaxanthin\nSynthesis by Komagataella phaffii through\nMetabolic and Fermentation\nEngineering

Astaxanthin is a kind of carotenoid with a strong antioxidant\nability,\nwhich has shown broad applications in the areas of healthcare, medicine,\ncosmetics, food additives, and aquaculture. With the increasing demand\nfor natural products, the microbial production of astaxanthin has\nbecome a new hot spot. In this study, the astaxanthin synthesis pathway\nwas first metabolically constructed in Komagataella\nphaffii (K. phaffii)(Pichia pastoris). By exploring the\ncombination of different promoters, astaxanthin producers were obtained.\nThen, the key enzymes in the astaxanthin synthesis pathway were explored,\nand different enzyme assembly strategies and an increase in NADPH\nsupply were used to improve the astaxanthin production. Furthermore,\nfermentation parameters including temperature, the concentration of\nthe carbon source, nitrogen sources, metal ions, BHT (2,6-di-<i>tert</i>-butyl-4-methylphenol), and Tween-80 were comprehensively\ninvestigated for the microbial growth and astaxanthin synthesis. Finally,\nthe astaxanthin production reached 716.13 mg/L by fed-batch fermentation\nin a 5 L bioreactor, which was the highest production of astaxanthin\nsynthesized by K. phaffii.