Astaxanthin is produced by Xanthophyllomyces dendrorhous as its principle
carotenoid but the production in the wild type strain is relatively low. A stable astaxanthinhyperproducing
strain, M34, was obtained in our previous work from N-methyl-N’-nitro-Nnitrosoguanidin
mutagenesis. In this study the wild type and M34 strains were compared in
terms of growth and carotenoid production. The expression levels and nucleotide sequences of
carotenogenic genes idi, crtE, crtYB, crtI, crtR and crtS of both strains were studied by realtime
polymerase chain reaction and polymerase chain reaction respectively. Gene expression
results indicated that both crtE and crtS genes showed significantly higher expressions
relative to the wild type throughout the production cycle, the highest being 1.3-fold and 3.8-
fold respectively. The six carotenogenic genes exhibited a total of 38 nucleotide changes after
mutation, including a missense mutation in idi gene (glutamic acid→alanine) and crtI gene
(histidine→glutamine), and two missense mutations in crtE (lysine→arginine;
serine→aspartic acid) and crtR genes (serine→valine; glutamine→proline).