ABSTRACT
We evaluated an astaxanthin overproducing Phaffia rhodozyma JMU-MVP14, and developed astaxanthin high-yielding fermentation process. We analyzed several fermentation parameters, i.e., biomass, astaxanthin and total carotenoids content to compare the characteristics of P rhodozyma JMU-MVP14 and the original strain through flask fermentation experiments. We conducted batch and fed-batch fermentation experiments in 7 L fermentor to investigate the effects of pH controlling models and feeding medium compositions on the production of astaxanthin. We further evaluated the capability and practical value of P rhodozyma JMU-MVP14 by fed-batch cultivation in the 1 m3 fermentor. Flask fermentation experiments revealed that P. rhodozyma JMU-MVP14 produced high yield of astaxanthin and carotenoids with specific productivity of astaxanthin and specific productivity of total carotenoids of 6.01 mg/g and 10.38 mg/g. Results of batch culture experiments in the 7 L fermentor showed that controlling the pH by ammonia auto-feeding was better than discontinuously adjusting pH value at 6.0 with regard to the high productivities of biomasses and astaxanthin. This P. rhodozyma strain synthesized astaxanthin partially linked to the growth with the Ks and pmax of 0.20 h ' and 21.73 g/L, respectively. Results of batch-fed fermentations in 7 L fermentor indicated that the complex feeding medium consisted of 50% glucose, 0.5% yeast extract and 0.3% corn steep syrup had lower astaxanthin productivity than the simple feeding medium containing only 50% glucose, which produced biomass, volumetric productivity of astaxanthin, volumetric productivity of total carotenoids, specific productivity of astaxanthin and total carotenoids at 32.81 g/L, 155.99 mg/L, 4.94 mg/g, 399.99 mg/L and 12.19 mg/g, respectively. As fed-batch cultured in 1 m3 fermentor, P rhodozyma JMU-MVP14 yielded 85.11 g/L of biomass, 279.96 mg/L of volumetric productivity of astaxanthin, 618.01 mg/L of volumetric productivity of total carotenoids, 3.29 mg/g of specific productivity of astaxanthin and 7.26 mg/g of specific productivity of total carotenoids. Additionally, P rhodozyma JMU-MVP14 cell contained 21.54% of protein, 41.34% of carbohydrate and 34.31% of lipid. These comprehensive results suggest that P. rhodozyma JMU-MVPl14 has great practical prosperity related to its strong ability to produce astaxanthin and good value byproducts.