Fabrication of doughnut-shaped particles from spheroidal paramylon granules of Euglena gracilis using acetylation reaction

► Chemical modification of paramylon, the micro-sized granular storage carbohydrate (β-1,3-glucan) of Euglena. ► Acetylation induces transformation from a spheroidal to a doughnut-shape of paramylon granules. ► Doughnut formation primarily hinges on preferential removal of central area of granules by acetylation.