A novel screening strategy utilizing aniline blue and calcofluor white to develop paramylon-rich mutants of Euglena gracilis

Paramylon, derived from Euglena gracilis, has been widely used as an immune-functional ingredient. To meet the increasing industrial demand, the development of paramylon-rich strains through random mutagenesis can be employed. Nevertheless, efficient methods for screening Euglena strains with high paramylon contents among the numerous available strains are currently lacking. This study developed a breakthrough screening method using two fluorescent dyes. Firstly, the aniline blue, highly specific to paramylon, was used for rapid screening, and then, the calcofluor white, permeable to the cell membrane, was used to visualize the paramylon contents of the first screened strains. By applying this novel screening strategy to 190 UV-induced strains, a superior strain, UV1, which has a high paramylon content of 73 % and showed 37 % higher paramylon productivity than the wild -type strain, was selected. This new screening method will contribute to develop other Euglena strains with high paramylon productivity and content using random mutagenesis.