Enhancement Of Astaxanthin Production In Saccharomyces Cerevisiae By Adaptive Evolution

Astaxanthin is a natural carotenoid with strong antioxidant properties and has great market value in industries such as food and medicine.Due to the complexity of chemical synthesis intermediates and the lack of safety,biosynthetic methods have received extensive attention.In this study,an adaptive evolutionary strategy combining atmospheric and room temperature plasmas mutagenesis(ARTP)and hydrogen peroxide stimulation was used to significantly increase the astaxanthin production in the Saccharomyces cerevisiae.The main work is as follows:1.The astaxanthin synthesis pathway was constructed in Saccharomyces cerevisiae by combining ?-carotene ketolase and hydroxylase from different sources to obtain astaxanthin production strain.Then,taking the yeast as the original strain,the integrated ARTP physical mutagenesis and hydrogen peroxide chemical mutagenesis alternately drive the strains for adaptive evolution,and finally three mutants with significantly improved production of astaxanthin were screened.The yields were 59.36 mg/L,63.22 mg/L,and 65.93 mg/L,respectively,which were 3.48 times,3.77 times,and 3.98 times higher than the original strain.2.The three strains with the highest yield of astaxanthin obtained by adaptive evolution were subjected to genome-wide resequencing analysis,and comparative genome analysis was conducted with the original strain.Key targets related to transcriptional regulation,cell membrane synthesis,pressure response and carbon source utilization were found.3.The mutant strain with the highest yield of astaxanthin was selected to optimize the fermentation process of 5 L fermenter.The growth(30 °C)and production(20 °C)two-stage temperature change strategy were used to make the production of astaxanthin in the 5 L fermenter reach 404.78 mg/L,which is the highest yield of astaxanthin in S.cerevisiae has been reported.