Effects of oxygen supply on growth and carotenoids accumulation by Xanthophyllomyces dendrorhous

The effects of oxygen supply on growth and carotenoids accumulation by Xanthophyllomyces dendrorhous were studied. Initial volumetric oxygen transfer coefficients (K(L)a) within the range 21.5-148.5 h(-1) had significant effects on growth and carotenoids accumulation, and an increase of the initial K(L)a value led to higher carotenoids, astaxanthin and biomass yields by X. dendrorhous. At an initial K(L)a value of 148.5 h(-1), a maximal cell concentration of 19.37 g 1(-1) and optimal carotenoids and astaxanthin productions of 18.1 and 14.5 mg 1(-1) were obtained, as well as a maximal astaxanthin content of 0.8 mg g DCW(-1), respectively. A higher oxygen supply was advantageous to astaxanthin biosynthesis and the ratio of astaxanthin in the total carotenoids. An increasing initial K(L)a value gave stronger fluorescence intensities by X. dendrorhous, resulting in the maximal intensity of fluorescence at the K(L)a value 148.5 h(-1). The cell growth of X. dendrorhous was significantly inhibited when dissolved oxygen tension (DOT) was controlled at approximately 20% air saturation, which was due to the oxygen limitation in broth. The astaxanthin yield and content at approximately 50% DOT were higher than those at approximately 20% DOT.