Enhanced Biomass and Paramylon Production of Euglena gracilis under Photo-mixotrophic Culture Conditions by Symbiotic Bacteria

摘要

Euglena gracilis, a unicellular green microalga, synthesizes and accumulates a variety of valuable products depending on culture conditions. E. gracilis produces a unique metabolite, paramylon (β-1,3-glucan) under heterotrophic and photo-mixotrophic conditions. Paramylon has several medical functions such as anti-tumor activity, anti-HIV activity, anti-infection activity, and cholesterol lowering effect. Enhancement of the growth of E. gracilis is critical to creating a highly efficient paramylon production system. On the other hand, microalgal growth and metabolisms are affected by the symbiotic bacteria. Therefore, the objectives of this study was to investigate the positive effects of indigenous bacteria in sewage effluent on E. gracilis's growth and paramylon production. In this study, E. gracilis was cultured in autoclaved or un-autoclaved sewage effluent supplemented with corn streep liquor, which is organic and nitrogen source for E. gracilis, under photo-mixotrophic condition. Growth of E. gracilis was significantly enhanced by indigenous bacteria in sewage effluent. More than 40 symbiotic bacterial strains were isolated from E. gracilis-sewage effluent culture. The most of symbiotic bacteria belong to Betaproteobacteria. Some of symbiotic bacteria enhanced growth and paramylon productivity of E. gracilis under photo-mixotrophic conditions. Acknowledgements: This study was supported in part by the ALCA Program of JST.