Studies On Breeding And Characteristic Analysis Of Phaffia Rhodozyma For Astaxanthin Over-production

Astaxanthin(3, 3'-dihydroxy-β,β'- carotene–4, 4'-dione), a kind of carotenoid, which is widely existed in biology. It has a lot of biological functions including antioxidation, antitumor, antiradiation, antidecrepitude, enhancing immunity and so on. As a result, astaxanthin possesses a high market value to food, aquaculture, medical treatment and feed industry.Phaffia rhodozyma is an important source of natural astaxanthin. Nowadays, the astaxanthin productivity is very low in wild strain of Phaffia rhodozyma, and it can't meet the increasing demand. Consequently, the most important task is to screen wide range of temperature, fast cell growth rate, and astaxanthin-hyperproducing mutants for potential commercial application. In this research, UV, Ar+ and NTG in turn were used to treat Phaffia rhodozyma in order to improve astaxanthin yield and its ferment temperature. The death rate and positive mutation rate were calculated and the proper mutagenicity dose was chosen. After a series of selections, mutants with fast cell growth rate and high astaxanthin productivity were obtained. The genetic stability and pigment ingredient of the mutants were studied, too.The research on mutagenesis showed: The death rate of Phaffia rhodozyma, treated with Ar+ ions implantation, presented unique"saddle shape". The death rate of Phaffia rhodozyma increased after treated for 0-3 min and decreased between 3-7 min. But the death rate curve ascended again when the treatment time exceeded 9 min. The maximun positive mutation reached 36.72% at 7 min. The death rate of Phaffia rhodozyma was 70%-95% after irradiated with UV for 3-9 min. From center to fringe of the plate there is a clear density gradient around the filter paper with NTG, less colonies at the center area, more colonies at the fringe area.The cell growth and astaxanthin content had changed after the treatment. In the Ar+ ions implantation experiment, an over-producing mutant GAR226 was obtained by means of low energy Ar+ beam treatment. Its astaxanthin yield reached 7850μg/L and astaxanthin content reached 592.5μg/g dry-cell-weight by flask cultures, which were 119.83% and 96.45% higher than the parent strain GY826, respectively. In the UV irradiation experiment, an over- production mutant GUV49 was obtained. Its astaxanthin yield reached 10321μg/L and astaxanthin content reached 713.8μg/g dry-cell-weight by flask cultures, which were 31.48% and 20.47% higher than the parent strain GAR226, respectively. In the NTG experiment, we got an over-producing mutant GNG274. Its astaxanthin yield reached 16897μg/L and astaxanthin content reached 966.6μg/g dry-cell-weight by flask cultures, which were 63.71% and 35.42% higher than the parent strain GUV49, respectively.