Bioproduction and application of glycogen from red microalgae
| PhD ceremony: | A. Kristijarti |
| When: | October 21, 2025 |
| Start: | 11:00 |
| Supervisors: | prof. dr. M.J.E.C. (Marc) van der Maarel, prof. dr. ir. H.J. (Hero Jan) Heeres, F. (Francesco) Picchioni, Prof |
| Where: | Academy building RUG / Student Information & Administration |
| Faculty: | Science and Engineering |
Glycogen is a sugar polymer used by many organisms to store energy. It consists of long, highly branched chains of glucose and, due to this structure, can be rapidly broken down when extra energy is needed during exercise or food scarcity. In terms of structure and composition, glycogen closely resembles starch, which is used as a renewable material in various applications. Because of its structure and similarities to starch, glycogen could serve as an alternative to starch in certain applications, such as in cosmetics and sports nutrition.
The most commonly used sources of glycogen are sweetcorn and oysters. An alternative source is the Galdieria microalga, which occurs in acidic hot springs. These microalgae can grow both in the light as well as in the dark on sugar and oxygen. In this doctoral research, Ima Kristijarti studied various Galdieria strains from three different volcanic regions around the world. These microalgae produce remarkably large amounts of glycogen in the dark on sugar and oxygen, with a unique structure that, unlike oyster or human glycogen, makes it particularly suitable for long-term energy storage.
Kristijarti also investigated how this algal glycogen can be chemically modified for use in stable oil-in-water emulsions or as an antioxidant. Finally, she examined in detail the water-binding properties, which are relevant for applications in skincare products. Taken together, it was established that glycogen from Galdieria microalgae—thanks to its high yield, unique structure, and modifiability—can serve as a good alternative to oyster glycogen or starch.