Isolation of a Stable Astaxanthin-Hyperproducing Mutant of Xanthophyllomyces dendrorhous Through Random Mutagenesis

Abstract

Astaxanthin is a red xanthophyll pigment which is widely commercially used due to its strong antioxidant properties. The heterobasidiomycetous yeast, Xanthophyllomyces dendrorhous, is one of the main microorganisms for industrial production of astaxanthin. However, astaxanthin content is low in wild type yeast strain. In our study, we had successfully isolated X. dendrorhous mutant with higher astaxanthin production capacity using chemical mutagen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), through β-ionone screening. The astaxanthin-hyperproducing mutant X. dendrorhous M34 had total carotenoid yield of 602.4 µg/g DW and a 110.8% increment of total carotenoid content compared to wild type. Survival studies indicated that MNNG treatment of yeast led to higher lethality in recipient cells compared to ethyl methanesulfonate (EMS) one. EMS-mutated strains did not show promising carotenoid yield during the screening process by β-ionone and the rate of reverse mutation was very high. In the stability test, no reversion was observed in X. dendrorhous M34 mutant after 10 successive transfers in culture broth. Reversed-phase HPLC showed that the elution profiles of carotenoid extracts of M34 and wild type X. dendrorhous were in agreement with the authentic standard and the major peak in M34 extract was identified as astaxanthin. The stable mutant with high yield of astaxanthin obtained in this work could be a suitable candidate for the industrial-scale production of astaxanthin.