Enhanced heterotrophic β-glucan production from a UV-induced Euglena gracilis mutant screened using a novel method under optimized cultivation conditions

The β-glucan produced by Euglena gracilis has emerged as an alternative to traditional high-value biomolecule sources such as yeast and fungi to meet the rising demand. A UV-induced mutant strain, E. gracilis UV199, was developed using a novel aniline-blue-based screening method to increase production. The response surface methodology was used to optimize the growth medium, resulting in glucose and monosodium glutamate concentrations of 25.9 and 5.8 g/L, respectively, and 0.9 × Hutner medium. Using this medium resulted in a β-glucan productivity of 3.62 g/L/day, which was 114% higher than that achieved using the wild type E. gracilis. Productivity was further increased to 4.29 g/L/day through optimizing pH and temperature to 4.5 and 32 °C, respectively. A comprehensive framework was constructed for increasing microalgal β-glucan production through integrating strain and process development. Combining UV mutagenesis, rapid screening, and optimizing heterotrophic culture conditions is an effective strategy for producing functional biomaterials from E. gracilis, supporting its future commercialization in food, pharmaceutical, and cosmetic industries.