2.1. Strains and culture conditions

X. dendrorhous CBS 6938 was purchased from Westerdijk Fungal Biodiversity Institute. The strain was maintained on potato dextrose agar slants at 4°C. One colony was selected and inoculated into a shake flask with 50 mL of potato dextrose medium and cultured at 20°C for 48 h. Then 80 mL of the seed liquid was inoculated into a 5 L bioreactor for batch fermentation. The standard culture conditions were: temperature, 20°C; agitation, 200 rpm; natural pH; air‐flow, 1 vv⁻¹m⁻¹. The overall production period of fermentation culture was 10 days with samples taken at 6 or 12 h intervals, during which dry cell weight (DCW), astaxanthin production, and glucose consumption were monitored. All experiments had three repetitions.