Perfusion culture process plus H2O2 stimulation for efficient astaxanthin production by Xanthophyllomyces dendrorhous.

A semicontinuous perfusion culture process (repeated medium renewal with cell retention) was evaluated together with batch and repeated fed-batch processes for astaxanthin production in shake-flask cultures of Xanthophyllomyces dendrorhous. The perfusion process with 25% medium renewal every 12 h for 10 days achieved a biomass density of 65.6 g/L, a volumetric astaxanthin yield of 52.5 mg/L, and an astaxanthin productivity of 4.38 mg/L-d, which were 8.4-fold, 5.6-fold, and 2.3-fold of those in the batch process, 7.8 g/L, 9.4 mg/L, and 1.88 mg/L-d, respectively. The incorporation of hydrogen peroxide (H(2)O(2)) stimulation of astaxanthin biosynthesis into the perfusion process further increased the astaxanthin yield to 58.3 mg/L and the productivity to 4.86 mg/L-d. The repeated fed-batch process with 8 g/L glucose and 4 g/L corn steep liquor fed every 12 h achieved 42.2 g/L biomass density, 36.5 mg/L astaxanthin yield, and 3.04 mg/L-d astaxanthin productivity. The lower biomass and astaxanthin productivity in the repeated fed-batch than in the perfusion process may be mostly attributed to the accumulation of inhibitory metabolites such as ethanol and acetic acid in the culture. The study shows that perfusion process plus H(2)O(2) stimulation is an effective strategy for enhanced astaxanthin production in X. dendrorhous cultures.