Journal Article

Efficient screening for astaxanthin-overproducing mutants of the yeast <i>Xanthophyllomyces dendrorhous</i> by flow cytometry

Ken Ukibe, Tohoru Katsuragi, Yoshiki Tani and Hiroshi Takagi

in FEMS Microbiology Letters

Volume 286, issue 2, pages 241-248
Published in print September 2008 |
Published online August 2008 | e-ISSN: 1574-6968 | DOI: https://dx.doi.org/10.1111/j.1574-6968.2008.01278.x

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Abstract

Astaxanthin possesses higher antioxidant activity than other carotenoids and, for this and other reasons, has great commercial potential for use in the aquaculture, pharmaceutical, and food industries. The basidiomycetous yeast Xanthophyllomyces dendrorhous is one of the best natural producers of astaxanthin, but wild-type cells accumulate only a small amount of astaxanthin. In this study, we developed an efficient flow cytometry method to screen for astaxanthin-overproducing mutants of X. dendrorhous. We first examined the relationship between cellular astaxanthin content and the intensity of fluorescence emitted from the cell. Although the fluorescence emission maximum of astaxanthin dissolved in acetone occurred at 570 nm, intracellular astaxanthin content correlated better with emission at around 675 nm in different X. dendrorhous strains. Using this emission wavelength, we screened cells mutagenized with ethyl methanesulfonate and successfully isolated mutants that produced 1.5–3.8-fold more astaxanthin than parent cells. This method enabled us to obtain overproducers five times more efficient than conventional screening from plate culture.

Keywords: Xanthophyllomyces dendrorhous; astaxanthin; screening; flow cytometry

Journal Article.  4185 words.  Illustrated.

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