IMPROVEMENT OF ASTAXANTHIN PRODUCTION BY PHAFFIA-RHODOZYMA THROUGH MUTATION AND OPTIMIZATION OF CULTURE CONDITIONS

Phaffia rhodozyma strains were treated with the mutagenic agent NTG several times and plated onto yeast-malt agar containing beta-ionone as a selective medium. One of the NTG-treated strains (NCHU-FS301) produced considerably more astaxanthin than the parent CBS-6938 (strain NCHU-FS301 produced 1515.63 mug/g and CBS-6938 565.08 mug/l). When the kinetic parameters of the specific growth rate (mu) and specific astaxanthin productivity (qp) were used to judge the association between growth behavior and product formation, NCHU-FS301 was shown to be a more positive growth-associated fermentation type than the parent strain. A study of the effects of the carbon source on red pigment formation revealed that glucose could support the highest total astaxanthin production (7809.3 mug/l). Yeast extract was the best nitrogen source in supporting the highest total astaxanthin formation (8637.5 mug/l). When mixed nitrogen sources were used, a mixture of yeast extract, beef extract, and potassium nitrate (1 : 1 : 1) supported more pigmentation (8052.6 mug/l) than the other mixtures tested. Astaxanthin-overproducing mutants could be useful in providing a natural source of astaxanthin for the aquacultural industry.