Astaxanthin Fermentation Conditions Optimization Based On Metabolic Analysis

At present, astaxanthin is regarded as a carotene with ultra-antioxidant performance. Due to its powerful antioxidantive activities and pigmentation property, it has broad application prospects in the aquaculture, food additives, cosmetics, healthy care products and medicine. Even though there are many sources to get astaxanthin, recently there is increasing interest in astaxanthin biosynthesis from Phaffia rhodozyma. It is an important precondition for achieving industrialization to analyze and optimize cultivation parameters to enhance astaxanthin production. In this paper, cultivation parameters of Phaffia rhodozyma was optimized based on metabolic analysis. The research was carried out as follows:A reliable, suited reverse HPLC analysis method for determination of astaxanthin and other carotenoids was developed. The parameters of the method were validated. Furthermore, the impurities showed in chromatogram were identified as dehydro- astaxanthin, DCD (3,3'-didehydro-β,ψ-carotene-4,4'-dione), cis-astaxanthin, dehydro-DCD, torulene,γ-carotene andβ-carotene.Astaxanthin and carotenoid biosynthesis ability in different generation mutant stains were studied. The studied indicated that total carotenoids content, biomass and astaxanthin assay produced by the stains from first generation to 11th generation showed a growth while dehydro DCD andβ-carotene showed a decrease, which is coincident with improving the ability of biosynthesis astaxanthin of Phaffia rhodozyma.Effects of different concentration of carbon sources, nitrogen sources on astaxanthin biosynthesized by Phaffia rhodozyma mutant G027 were studied and analyzed. Results showed that the 8% of carbon source with max. astaxanthin production and less impurities was best concentration to enhance astaxanthin production under 50% DO(dissolved oxygen) and 0.4% nitrogen source;0.4% of nitrogen source with highest astaxanthin production and least impurities under 5% carbon source was best for astaxanthin biosynthesis.Effects of different temperatures, initiative pH rang and DO on astaxanthin and other carotenoids biosynthesis by mutant G027 were studied and analyzed. Results showed that 20°C, pH 5～6,50% DO was good for the stains to grow and biosynthesize astaxanthin and DCD, torulene,γ-Carotene andβ-carotene was less in these conditions; It was also founded lower DO caused a sharp decrease in biomass and astaxanthin production which was due to change of metabolism and oxidase damage.