Spore-Based Biocomposite Thermoplastic Polyesters with Enhanced Toughness and Programmable Disintegration

Thermoplastic polyesters are widely used in commodity and high-performance applications due to their tunable and exceptional properties, versatile performance, and increasing relevance in sustainable materials. Integrating biological functionality into these polymers offers a promising route to enhance performance and end-of-life behavior beyond what conventional additives can achieve. Here, we report the generalization of an embedded spore-based engineered living material concept to three representative thermoplastic polyesters; polycaprolactone (PCL), polylactic acid (PLA), and poly(butylene adipate-co-terephthalate) (PBAT). Heat-shock-tolerized Bacillus subtilis spores were compounded with each polyester as a living biofiller via hot melt extrusion. The resulting biocomposite polyesters retained high spore viability (>90%) after extrusion and exhibited improved mechanical performance (up to 41% toughness improvement compared to neat polymers). End-of-life behavior was evaluated in a microbially-limited composting environment, where spore-containing PCL exhibited nearly complete disintegration within five months, corresponding to a ∼7-fold increase in degradation kinetics relative to neat PCL. Finally, 3D printing of biocomposite PCL was demonstrated through fused deposition modeling and direct ink writing methodologies. Together, this work demonstrated the successful extension of spore-based engineered living materials from thermoplastic polyurethane to multiple thermoplastic polyesters.