Novel polycondensed biopolyamide generated from biomass-derived 4-aminohydrocinnamic acid

Area of Science:

• Biotechnology and Biopolymer Science
• Sustainable Chemistry
• Materials Science

Background:

• Biomass plastics offer a sustainable alternative to petroleum-based plastics for a carbon-neutral society.
• 4-aminocinnamic acid (4ACA), a biomass-derived aromatic amine, is a precursor for high-performance biopolymers like polyamides and polyimides.
• Efficient conversion of 4ACA to its hydrogenated form, 4-aminohydrocinnamic acid (4AHCA), is crucial for developing novel bioplastics.

Purpose of the Study:

• To develop a microbial catalyst for the efficient hydrogenation of 4ACA to 4AHCA.
• To synthesize and characterize high-molecular-weight poly(4AHCA) from the biomass-derived 4AHCA.
• To evaluate the thermal properties and potential applications of the resulting biopolyamide.

Main Methods:

• Screening of 10 microbial genes encoding enoate and xenobiotic reductases expressed in Escherichia coli for 4ACA conversion.
• Optimizing reaction conditions (pH, aerobic/anaerobic) for the most effective reductase, ca2ENR from Clostridium acetobutylicum.
• Polycondensation of the produced 4AHCA via dehydration to form poly(4AHCA) and subsequent characterization of its molecular weight and thermal properties.

Main Results:

• A recombinant E. coli strain expressing Clostridium acetobutylicum 2-enoate reductase (ca2ENR) achieved >95% mol/mol conversion of 4ACA to 4AHCA.
• The ca2ENR catalyst demonstrated high reaction rates under optimal pH 7.0 conditions, both aerobically and anaerobically.
• The synthesized poly(4AHCA) exhibited high molecular weight (M n = 1.94 MDa) and excellent thermal stability (T d10 = 394 °C, T g = 240 °C).

Conclusions:

• The developed microbial catalyst enables efficient production of 4AHCA from biomass-derived 4ACA.
• High-molecular-weight poly(4AHCA) synthesized from biomass shows promising thermal properties for high-performance engineering plastics.
• This work contributes to the development of sustainable bioplastics and a circular economy.