Programmable assembly of mechanically robust and functional polymer–spore biocomposites in organic solvent

Microbial biocomposites offer genetically programmable and regenerative
functionality, but their mechanical tunability remains limited by the mild
conditions required for biological activity and viability. Here, we report
the programmable self-assembly of Bacillus subtilis spores with
benzalcyanoacetate (BCA)-functionalized polymers to form robust composites
exhibiting tunable viscoelastic and tensile properties. Surface-exposed
cysteines on the spore coat react with BCA motifs, forming dynamic
thia-Michael networks with Young’s moduli of >100 MPa. Systematic
variation of BCA reactivity and comonomer-dependent polymer dynamics
enabled control over stiffness, stress-relaxation behavior, microscale
morphology, and covalent biocontainment. Incorporation of engineered
spores confers catalytic function that can be regenerated following
solvent-triggered disassembly. This work establishes a modular platform
for constructing biocomposites that are both mechanically and genetically
programmable, bridging the synthetic and biological domains through
molecularly defined interfaces.