Study On Astaxanthin Fermentation Conditions And Kinetics Of Phaffia Rhodozyma

Astaxanthin is a kind of carotenoids and the highest level production in of the content ofthe carotenoid.In nature, astaxanthin has the strongest oxidative stability. At present,becausethe natural astaxanthin has low yield and high production costs, it is hard to compete withchemical synthesis astaxanthin in the price.Astaxanthin is synthesized by mevalouic acid pathway. Synthesis of mevalouic acid isoriginated in acetylcoenzyme A. Pyroracemic acid is the prosoma of acetylcoenzyme A. So, itis important to study on pyroracemic acid for the improvement of astaxanthin yield. Theeffects of metal ions on astaxanthin production and extracellular pyruvate were investigated inthis paper by single factor and orthogonal erperiments. The result showed that astaxanthinincreasesd, with addition of the metal ions, while extracellular pyruvate deceased by singlefactor experiments. It means that the astaxanthin production was inversely related to theproduction of extracellular pyruvate. The orthogonal erperiments showed that effect of thefour metal ions on astaxanthin biosynthesis was in the order of Fe³⁺>Mn²⁺>Zn²⁺>Cu²⁺. Theoptimal concentrations of Mn²⁺, Zn²⁺, Fe³⁺, Cu²⁺were4μmol/L,3μmol/L,1μmol/L,4μmol/Lrespectively. In optimum conditions,the yield of astaxanthin was about9.13mg/L.In order to increase the astaxanthin production and biomass, the optimal carbon sourcewas glucose, the optimal nitrogen source was beef extract and ammonium citrate （the ratiowas1:2）by single factor experiments. Plackett-Burman experiments showed that glucose andcomplex nitrogen source had noticeable effect on astaxanthin. The optimal mediumcompositions as follows were glucose3.65%, complex nitrogen source0.45%by the steepestexperiment and the central composite design. Under the optimal condition, the highest yieldof astaxanthin was11.81mg/L, which increased190%compared with that of thenon-optimized condition.The different fed-batch fermentation methods of Phaffia rhodozyma were studied in thisarticle, which was expected to improve the yield of astaxanthin to have a positive effect onindustry production. The results showed that tomato juice feeding culture brought about the biggest astaxanthin yield15.71mg/L, astaxanthin yield reaching15.61mg/L was obtainedfrom exponential feeding culture, medium and alcoholic feeding culture brought about theastaxanthin yield14.21mg/L, there had the smallest production of astaxanthin13.21mg/L withpH-stat feeding. The production of astaxanthin yield had a huge difference due to differentfeeding culture methods.