The 25-2 astaxanthin-overproducing mutant is derived from the wild type P. rhodozyma ATCC 24202 ( Ramı́rez et al., 2000). The strain was grown in YM broth Difco (0.3% malt extract, 0.3% yeast extract; glucose and Bacto-peptone as carbon and nitrogen sources, as required) or Yucca medium (2 g l−1 KH2PO4, 0.5 g l−1 SO4Mg, Sigma; supplemented with date juice and urea as carbon and nitrogen sources, as required). The main carbon sources in date juice were: 60% fructose and 40% glucose and which adjusted to a final concentration of 160 g reducing sugars l−1. The YM medium and Yucca medium were sterilized at 120°C for 20 min. The date juice was sterilized separately by autoclave and added to the Yucca medium, as required.