Three-Dimensional Hierarchical Cellulose Structures Based on Microbial Synthesis and Advanced Biofabrication

Cellulose is the most abundant and important biopolymer in our world, and it can also be biosynthesized by certain types of bacteria, such as Komagataeibacter xylinus. However, due to the requirement of oxygen access during such bacterial cellulose (BC) biosynthesis, as well as the high crystallinity and poor processability of BC, it is very challenging to fabricate 3D BC structures with well-defined shape, geometry, and internal structure. In recent years, the rapid progress of polymer additive manufacturing and biofabrication has provided new and versatile approaches for fabricating hierarchical 3D cellulose structures. This can be achieved by either incorporating BC in the 3D printing feedstock or, more interestingly, by incorporating cellulose-generating bacteria in a living ink followed by in situ BC biosynthesis. In this Perspective, we critically examine the potential of various advanced biofabrication technologies in fabricating hierarchical 3D cellulose structures, especially those based on integrating additive manufacturing with in situ microbial biosynthesis. Moreover, sustainable biocomposites based on BC and microbial biosynthesis are also discussed. The current challenges and future opportunities of microbial-biosynthesis-enabled 3D cellulose structures are highlighted. Their applications in tissue engineering, drug delivery, lightweight composites, thermal management, and energy storage are also discussed.