Carotenoid production and gene expression in an astaxanthin-overproducing Xanthophyllomyces dendrorhous mutant strain

The primary carotenoid synthesized by Xanthophyllomyces dendrorhous is astaxanthin, which is used as a feed additive in aquaculture. Cell growth kinetics and carotenoid production were correlated with the mRNA levels of the idi, crtE, crtYB, crtI, crtS and crtR genes, and the changes in gene sequence between the wild-type and a carotenoid overproducer XR4 mutant strain were identified. At the late stationary phase, the total carotenoid content in XR4 was fivefold higher than that of the wild-type strain. Additionally, the mRNA levels of crtE and crtS increased during the XR4 growth and were three times higher than the wild-type strain in the late stationary phase. Moreover, the nucleotide sequences of crtYB, crtI and crtR exhibited differences between the strains. Both the higher crtE and crtS transcript levels and the crtYB, crtI and crtR mutations can, at least in part, act to up-regulate the carotenoid biosynthesis pathway in the XR4 strain.