Studies On High-cell-density Culture And Kinetic Models Of Astaxanthin Fermentation By Phaffia Rhodozyma

Astaxanthin(ASTA) is one kind of carotenoids. Due to its natural characteristic pigmenting and special biological functions of preventing degenerative dieases in human i.e. cancer, cardiovascular disease, immune system decline, and scavenging free radicals.It has generated considerable interest for food, feed, cosmetic and pharmaceutical industry,but low-production of ASTA is a restricted factor of it. Aiming directly at this problem, High-cell-density fermentation process of Phaffia rhodozyma was studied in this paper by using biochemical reaction process technology. The main results are as follows:(1)The influence of different sugar-feeding strategies on cell growth and ASTA production by Phaffia rhodozyma fed-batch fermentation in 5 L reactor was investigated. The results showed that optimal sugar feeding depended on feeding time and pulse feeding was the best among all experiments, in which a significant increase (79% and 45% respectively) in production of ASTA and biomass was achieved in a pulse fed-batch process compared with a batch process.(2)Batch fermentation characteristics of Phaffia rhodozyma have been investigated using several classic kinetic models existing in the literature, and the applicability of these models was tested. The simulation results revealed an adequate fit of the modified Logistic and product prohibition model.(3)Based on the substrate inhibition model, we proposed a two-stage optimized feeding strategy for ASTA production of high-cell-density fermentation. Compared with those traditional feeding strategies, such as constant feeding, exponential feeding, pulse feeding, DO-stat and pH-stat fed-batch, the highest ASTA production(29.05 mg/L) and biomass(23.80 mg/L) was obtained respectively in the two-stage culture system, in which a significant increase(109% and 52.8% respectively) compared with a batch process.