Enhanced Astaxanthin Production in Rhodosporidium toruloides via Sequential Benomyl-EMS Mutagenesis and Culture Medium Optimization

Abstract

Astaxanthin is a valuable xanthophyll carotenoid with potent antioxidant activity and broad industrial applications. This study aimed to enhance astaxanthin production in Rhodosporidium toruloides through sequential chemical mutagenesis and medium optimization. Sequential mutagenesis using benomyl and ethyl methanesulfonate (EMS) generated mutant strain BE1, which produced 2519.39 ± 225.78 µg/L astaxanthin, a 5.70-fold increase over the wild-type strain. BE1 also showed improved growth kinetics, entering the exponential phase at 9 h and reaching maximum astaxanthin accumulation after 96 h. Medium optimization using response surface methodology identified an optimal formulation of 16.78 g/L glucose, 16.61 g/L peptone, and 11.61 g/L malt extract, further increasing astaxanthin production to 3397.13 ± 41.65 µg/L. The crude astaxanthin extract exhibited strong reducing power under the tested conditions. Overall, the combined strategy increased astaxanthin yield progressively from 442.00 µg/L in the wild-type strain to 3397.13 µg/L in the optimized BE1 culture. These findings demonstrate an effective strategy for improving astaxanthin biosynthesis and highlight the industrial potential of BE1 for natural astaxanthin production.