Raman-activated directed evolution of Euglena gracilis with quantum-beam mutagenesis

Biomaterials derived from microalgae are promising as a source of biofuels, drugs, cosmetics, and foods. Among different microalgae, Euglena gracilis has attracted attention for biomaterials production due to its high productivity of paramylon, a potential drug for HIV and colon cancer. To enhance the productivity of paramylon in E.gracilis, directed evolution is a promising approach. In general, directed evolution consists of three key steps: mutagenesis, selection, and amplification. For applying it to the enhancement of the paramylon productivity of E.gracilis, mutagenesis and selection steps are challenging because altering nuclear genome of E.gracilis is difficult due to its polyploid nature and no biomarker such as fluorescent dyes is available for quantifying paramylon. In this study, we tackle these difficulties by combining quantum-beam irradiation for mutagenesis and high-throughput Raman-activated cell screening for label-free selection.