Biocatalytic living materials built by compartmentalized microorganisms in annealable granular hydrogels

•Biocatalytic living materials are 3D printed from annealable granular hydrogels.•Each granular hydrogel hosts yeasts to preserve their high cellular viability.•The granular hydrogels are jammed to form bioinks for 3D printing.•Biocatalytic living materials show enhanced ethanol production rates. The field of living materials aims to use microorganisms as cell factories for drawing energy from their environment and to modulate the performance of the materials in some manner. Although the emergence of bioprinting techniques has given rise to the creating of living materials with rationally designed properties, a challenge is the controlling of the printability of the cell-laden bioinks while maintaining the high viability of cells. Here, we present an annealable granular hydrogel system that can encapsulate and compartment microorganisms for the 3D printing of biocatalytic living materials. Yeast-laden hydrogel microparticles (HMPs) are generated by a droplet-based microfluidic preparation process and then are jammed into granular hydrogels with shear-thinning and self-recovery behaviors. Upon extrusion-based 3D printing, the jammed HMPs are able to deposit into a designated structure and can be further annealed by interparticle cross-linking. Using HMPs as microorganism carriers, yeast cells are protected by encapsulation and survive shear forces during 3D printing. Further, printed constructs display enhanced catalytic activity, which show increased ethanol production due to improved mass transfer. The combination of annealable granular hydrogels and 3D printing should enable novel routes to produce microorganisms-based living materials with further applications in bioremediation, biosensing and biomedicine.