Study On Astaxanthin Biosynthesis From Phaffia Rhodozyma

Astaxanthin(ASTA), a nonprovitamin A oxygenated carotenoid, has powerful biological activities including antioxidant, antitumor and immuin enhancement effects. Meanwhile ,ASTA is an importment pigment for aquaculter industry, so the market of it is expanding.Recently there is increasing interest in ASTA biosynthesis from Phaffia rhodozymas for commercial production, but low-production of ASTA is a restricted factor of it. Aiming directly at this problem, this paper firstly studied on the breeding of the P.rhodozyma, by UV inducing protoplast, then optimized the medium and feimentation condition, the effect of regulating NADPH on ASTA production was discussed also. The results as follows: (1) Ascertaining the best way to prepare P.rhodozyma protoplasm by enzyma snail solution is that: the inoculum age is 18h, enzyme concentration is 1%, treated under 30℃for 2h, osmotic stabilizer for protoplasm formation and revival is 0.5 mol/L sucrose.By UV inducing the protoplasm, a high ASTA producing mutant was obtatined, compared with the initinal strain, the yield of ASTA was increased 86.5%. (2) Effects of carbon sources on ASTA biosynthesis by mutant was studied. Results showed that glucose and sucrose were advantageous with the similar effects. The influence of medium contents on astaxanthin production was evaluated using a fractional factorial design. Sucrose and Yeast power influenced astaxanthin significantly. The path of steepest ascent was used to approach the optimal region of the medium concentration. The optimal concentrations of sucrose and Yeast power were determined by a central composite design and response surface analysis. The optimized medium was composed of sucrose 49.8g/L, yeast powder 9.6g/L, NH₄Cl 2g/L,KH₂PO₄·7H₂O 0.5g/L,CaCl₂·H₂O 0.3 g/L. (3) The culture conditions suitable for ASTA biosynthese from P.rhodozyma were established. The results of orthogonal designs L₈(2⁷) showed that The optimum temperature and pH for growth were 20℃and 5.5 respectively,and media volume was 30mL,the inoculation concentratons was 8%,with the shaker rotation speed 200 rpm. The ferment dynamic after optimization was studied also, offering an experiment foundation for enlarging produce. (4) The relationship between nicotinamide adenine dinucleotide (NADPH) producing enzyme-glucose-6-phosphate dehyderogenase (G6PDH) and P.rhodozyma growth,ASTA biosynthese was studied.The results showed that G6PDH correlated with the others. Addition of 0.12g/L glutamate accelerated ASTA production. The mechanism of it was discussed , which provided a new thinking for metablic regulation.