Hydrogen peroxide-induced astaxanthin biosynthesis and catalase activity in Xanthophyllomyces dendrorhous

Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma) in shake-flask cultures was exposed to 10-20 mmol/L H2O2at various culture stages, and the astaxanthin production was significantly increased by H2O2fed at 0 or 24 h (exponential phase), but only slightly at 48 h (near stationary phase). The astaxanthin production was enhanced most significantly with double feeding of 10 mmol/L H2O2at 0 and 24 h, reaching a cellular content of 1.30 mg/g cell and a volumetric yield of 10.4 mg/L, which were 83 and 65% higher, respectively, than those of the control (0.71 mg/g cell and 6.3 mg/L). The intracellular catalase (CAT) activity was also increased after H2O2treatment. The increases in CAT and astaxanthin of cells could be detected within 4 h of H2O2treatment. The increase in the astaxanthin content of cells was concomitant with a notable decrease in the β-carotene content. The older yeast cells at late culture stage (120 h), due perhaps in part to their higher astaxanthin contents, were more tolerant to H2O2toxicity than the younger cells (24 h). No enhancement of the astaxanthin biosynthesis was attained when H2O2was added to the yeast culture together with a sufficient amount of exogenous CAT. The results suggest that astaxanthin biosynthesis in X. dendrorhous can be stimulated by H2O2as an antioxidative response.