Investigations in mutation breeding and culturing media by Xanthophyllomyces dendrorhous

Astaxanthin is a red-orange carotenoid compound that has been used as antioxidant, pigment, and immunopotentiator. Xanthophyllomyces dendrorhous is a promising source for natural astaxanthin. In order to improve the astaxanthin production capacity of X. dendrorhous AS2.1557 (designated WT), nitrosoguanidine (NTG), ultraviolet (UV), and atmospheric and room temperature plasma (ARTP) mutagenesis techniques were applied for mutation breeding. The astaxanthin yield was elevated stepwisely after three-staged mutagenesis: Firstly, WT strain was treated with NTG and thus resulted in a positive mutagenic strain As1-3 with higher astaxanthin production; subsequent, strain As1-3 was exposed to UV irradiation, thereby generating a positive mutagenic strain As2-3; finally, a positive mutant As3-8 was developed by ARTP-induced mutagenesis of strain As2-3. After 72 h of cultivation in yeast extract-peptone-dextrose (YPD) medium, the astaxanthin titer and content produced by strain As3-8 were determined to be 4.45 mg·L−1 and 0.96 mg·g−11, which were 8.24 and 11.95 times that of WT strain, respectively. Afterward, the culture medium composition was optimized using the Plackett-Burman design (PBD), Box-Behnken design (BBD) and response surface methodology (RSM), the astaxanthin titer and content of As3-8 were determined to be 13.05 mg·L−1 and 2.04 mg·g−1 dry biomass after 96 h of cultivation in the optimized medium TM2, 24.17-/25.36-fold of the amounts of WT strain. This study provides a good reference for the enhancement of microbial metabolite production by using mutation breeding and medium optimization, the obtained mutant As3-8 would be an interesting candidate for comparative genomics and transcriptomics analysis-guided metabolic engineering in the future.