Fermentation Optimization of Astaxanthin Produced by Phaffia Rhodozyma Based on Cerium Nitrate Regulation
Astaxanthin is a vital important carotenoid widely used in food,pharmaceutical,feed,and cosmetics industries according to its strong antioxidant,anti-cancer,and significant staining abilities.Phaffia rhodozyma is a promising yeast to produce natural astaxanthin while its production can be enhanced remarkably by metabolic regulation and fermentation optimization.The paper uses cerium nitrate as a chemical inducer to regulate astaxanthin production in red yeast and optimizes the culture medium and fermentation operation mode.The results indicated that astaxanthin production at dose of 50 mg/L with cerium nitrate added at 12th hour,was 34.92％higher than the initial control,while the reactive oxygen species concentration and gene expression of crtE,crtⅠ,crtYB and ast were significantly up-regulated at dose of 50 mg/L with cerium nitrate added at 12th hour.Then,based on the positive regulation of cerium nitrate,three main ingredients in fermentation medium including glucose,yeast extract and cerium nitrate,were optimized employing response surface methodology.The results showed that the astaxanthin production of 1.244 mg/L was increased by 50.11％compared with the initial control with optimal concentrations of glucose,yeast extract and cerium nitrate were 24.1 g/L,1.4 g/L and 45.9 mg/L,respectively.Meanwhile,based on the 5 L mechanical agitating fermentation tank,astaxanthin production of 13.28 mg/L in batch-feed fermentation were 3.67-fold and 16.54-fold compared with that in batch fermentation and the initial control,respectively.
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