Improvement of astaxanthin production by Phaffia rhodozyma through mutation and optimization of culture conditions

Abstract

Phaffia rhodozyma strains were treated with the mutagenic agent NTG several times and plated onto yeast-malt agar containing β-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 μg/g and CBS-6938 565.08 μg/ l). When the kinetic parameters of the specific growth rate (μ) and specific astaxanthin productivity ( q p) 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 μg/ l). Yeast extract was the best nitrogen source in supporting the highest total astaxanthin formation (8637.5 μg/ 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 μg/ l) than the other mixtures tested. Astaxanthin-overproducing mutants could be useful in providing a natural source of astaxanthin for the aquacultural industry.