Screening and fermentation optimization of a high-yield-astaxanthin-producing Phaffia rhodozyma

Objective: To screen out a high- yield- astaxanthin- producing Phaffia rhodozyma and optimize the culture medium conditions.Method: Phaffia rhodozyma strain( P.rhodozyma 02) was used as original strain treated with UV- Li Cl and60Co- γ mutagenesis respectively.Mutant strains with higher astaxanthin productivity were screened out and used as the starting strains for genome shuffling. After 5 rounds of protoplast fusion,obtained the best recombinant with further high yield of astaxanthin.The optimum culture medium conditions was obtained by adding natural promoter rich in synthetic precursor of astaxanthin to the medium and optimizing the parameter of culture medium.Result: a high- yield- astaxanthin- producing recombinant F5- 9 was obtained and the optimum culture medium conditions were: glucose 30.0 g / L,peptone 3.0 g / L,yeast extract powder 7.0 g / L,( NH₄)_2SO₄5.0 g / L,Mg SO₄·7H₂O 2.75 g / L,KH₂PO4 1.5 g / L,Ca Cl₂·2H₂O 0.2 g / L,carrot juice 150 mg / L. Eventually the astaxanthin production reached at( 83.39 ± 1.03) mg / L,which was 17.56 times than the original strain. Conclusion: The traditional mutation and genome shuffling can significantly improve the yield of astaxanthin and there is room for further improvement in the yield of astaxanthin by adding natural promoter rich in synthetic precursor of astaxanthin carrot juice into culture medium.