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 H₂O₂ at various culture stages, and the astaxanthin production was significantly increased by H₂O₂ fed 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 H₂O₂ at 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 H₂O₂ treatment. The increases in CAT and astaxanthin of cells could be detected within 4 h of H₂O₂ treatment. 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 H₂O₂ toxicity than the younger cells (24 h). No enhancement of the astaxanthin biosynthesis was attained when H₂O₂ was 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 H₂O₂ as an antioxidative response.