Artificial Symbiosis for Bulk Production of Bacterial Cellulose Composites.

Symbiotic relationships between micro-organisms are key to the function of all global ecosystems. Here we extrapolate this concept for biomaterial fabrication by creating artificial symbiotic relationships between species that are usually not grown synergistically in nature. Specifically, we combine the cellulose-producing bacterium Komagataeibacter hansenii and the green microalga Chlamydomonas reinhardtii to obtain bulk growth of bacterial cellulose. Usually, bacterial cellulose is produced as floating pellicles at the air-liquid interface of the growing media, because free oxygen, together with the nutrients in the culture medium, is required for the bacteria to synthesize the cellulose fibers. In the co-culture, bacterial cellulose production can be achieved in bulk beyond the spatial restriction of the air-liquid interface as the motile microalgae with photosynthetic activities act as oxygen-generating sites within the culture medium. In exchange, the highly porous and mechanically robust scaffold provided by the cellulose allows the algal-bacterial community to form a bio-composite up to several centimeters in thickness. We demonstrate that this symbiotic growth platform allows the simultaneous production of bulk bacterial cellulose in static incubation conditions, taking up an arbitrary and yet tunable 3D shape, dependent on the geometry of the culture vessel.