| Astaxanthin is a high-value additive carotenoid with different physiological functions.Phaffia rhodozyma has the natural ability of producing astaxanthin and has some advantagesjust like shorter period of fermentation,easy to culture in a high density.Nowadays manyresearches are focused on breeding high-producing strains and optimizing culture conditions.Paper from natural samples screened a strain producing astaxanthin, be namedS6.Physiological and biochemical identification of this bacterium beach red yeast rhodotorula.This paper studied the use of single factor experiment mutant UV-801e-S015of theshake flask fermentation conditions.Were investigated the initial fermentation medium pH, aswell as the kinds of age, inoculum size, medium volume (dissolved oxygen), fermentationtemperature and other factors on the growth of Phaffia yeast as well as the astaxanthinsynthesis.the results were the initial pH value of5.0, seed age48h, inoculum concentration12%,25mL/250mL flask of liquid volume, temperature20℃, in this condition fermentedastaxanthin production can be achieved7.61mg/L.The metabolic network of Phaffia rhodozyma UV-801e-S015for astaxanthinbiosynthesis was developed based on the stoichiometric balance equations to illustrate thecarbon flux distribution of intermediates and metabolites. The metabolite flux distribution andalteration among pathways during diverse batch culture phases were calculated by using themetabolic flux analysis method. Subsequently, the carbon flux of glutathione biosynthesis wasadjusted by two-stage temperature control of switching temperature from20℃to16℃,oraddition of1%ethanol to the culture. The production of astaxanthin was13.9mg/L and10.73mg/L respectively. It was indicated that the production of astaxanthin was increased by82.71%and41.35%, respectively. Moreover, the mechanisms of the over-production ofastaxanthin with the above-mentioned culture strategies were interpreted with the principlesof metabolic engineering. |
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