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

Area of Science:

• Materials Science
• Biotechnology
• Polymer Chemistry

Background:

• Thermoplastic polyesters are versatile materials with growing importance in sustainable applications.
• Integrating biological components offers a novel approach to enhance polymer performance and end-of-life properties.
• Engineered living materials (ELMs) represent a new frontier in smart and responsive materials.

Purpose of the Study:

• To generalize the embedded spore-based ELM concept to common thermoplastic polyesters.
• To investigate the impact of incorporating heat-shock-tolerized Bacillus subtilis spores into polycaprolactone (PCL), polylactic acid (PLA), and poly(butylene adipate-co-terephthalate) (PBAT).
• To evaluate the mechanical properties, spore viability, end-of-life behavior, and 3D printability of these novel biocomposite polyesters.

Main Methods:

• Compounding heat-shock-tolerized Bacillus subtilis spores with PCL, PLA, and PBAT using hot melt extrusion.
• Assessing spore viability post-extrusion.
• Evaluating mechanical performance, including toughness.
• Conducting microbially-limited composting tests to determine degradation rates.
• Demonstrating 3D printing capabilities using fused deposition modeling and direct ink writing.

Main Results:

• High spore viability (>90%) was maintained after hot melt extrusion in all tested polyesters.
• Biocomposite polyesters exhibited improved mechanical properties, with up to a 41% increase in toughness.
• Spore-containing PCL showed significantly accelerated degradation in composting, with nearly complete disintegration in five months (approx. 7-fold increase).
• Successful 3D printing of biocomposite PCL was achieved.

Conclusions:

• The embedded spore-based ELM concept is successfully extended to multiple thermoplastic polyesters (PCL, PLA, PBAT).
• These biocomposite materials offer enhanced mechanical performance and improved biodegradability.
• This research paves the way for developing next-generation sustainable and functional materials through bio-integration.