Biofabrication of Renewable Polyesters

Introduction

Polyesters—widely used in textiles, packaging, and engineering plastics—are typically made from fossil-based monomers like terephthalic acid and ethylene glycol. Their growing environmental impact has led to increasing interest in renewable polyesters, which are derived from bio-based monomers through biofabrication—the biological production of materials using engineered microbes, enzymes, and fermentation processes.

Biofabrication of renewable polyesters involves designing biosynthetic pathways to produce key monomers from sugars, waste biomass, or CO₂, followed by enzymatic or microbial polymerization. These materials are not only biodegradable (in some cases) but also reduce carbon emissions and align with the principles of a circular bioeconomy.

What Products Are Produced?

• Polylactic Acid (PLA) – Compostable polyester used in packaging and 3D printing
• Polyhydroxyalkanoates (PHA) – Biodegradable polyesters from microbial fermentation
• Polybutylene Succinate (PBS) – Bio-based polyester from succinic acid and BDO
• Bio-PET – Partially renewable (bio-ethylene glycol) alternative to PET
• Poly(3-hydroxypropionate) – From bio-based 3-HP for specialty applications

Pathways and Production Methods

1. Monomer Biosynthesis via Engineered Microbes

• Lactic acid → via Lactobacillus fermentation
• Succinic acid, 1,4-butanediol (BDO), 3-hydroxypropionic acid (3-HP) → via engineered E. coli, Corynebacterium glutamicum, Yarrowia lipolytica

2. Fermentation to PHA

• Direct microbial polymerization by bacteria like Cupriavidus necator or Halomonas
• Substrates: glucose, glycerol, plant oils, waste streams

3. Polymerization Processes

• Ring-opening polymerization (ROP) for PLA
• Enzymatic polymerization using lipases and esterases
• Chemical catalysis for PBS, bio-PET, and 3-HP-based polyesters

Catalysts and Key Tools Used

Microbial Hosts:

• E. coli, Lactobacillus, Cupriavidus necator, Halomonas, Bacillus subtilis

Enzymes and Catalysts:

• Lipases (e.g., CALB) for enzymatic polymerization
• Polymer synthases in PHA-producing microbes
• Metal catalysts (e.g., Sn(Oct)₂) for ROP of PLA

Synthetic Biology Tools:

• CRISPR-Cas9 for genome editing
• Pathway modularization and optimization
• Cofactor balancing and flux redirection

Case Study: NatureWorks’ PLA from Corn Sugar

Highlights

• Ferments glucose to lactic acid, followed by ROP to PLA
• Uses GMO-free Lactobacillus strain for lactic acid
• PLA used in food packaging, medical devices, 3D printing

Timeline

• 2002 – First PLA plant opened in Blair, Nebraska
• 2010 – PLA applications expanded to cutlery, textiles
• 2019 – High-heat PLA grades introduced
• 2023 – Carbon-negative PLA under development using renewable energy

Global and Indian Startups Working in This Area

Global

• NatureWorks (USA) – PLA leader with large-scale biorefineries
• Danimer Scientific (USA) – PHA and PHA blends
• Total Corbion (Netherlands) – PLA and lactide intermediates
• Tianan Biologic (China) – Industrial PHA production
• Newlight Technologies (USA) – AirCarbon PHA from methane/CO₂

India

• Praj Industries – Bio-based lactic acid and PLA pilot lines
• IISc Bangalore & CSIR-NCL – Bio-succinate and bio-PBS research
• Godavari Biorefineries – PHA and bio-polyester monomers
• IIT Delhi & ICT Mumbai – Enzymatic polyester polymerization platforms

Market and Demand

The global renewable polyester market is projected to grow from USD 8.5 billion in 2023 to USD 18.2 billion by 2030, at a CAGR of ~11.3%. Growth is fueled by demand for biodegradable packaging, sustainable fashion, and regulatory bans on single-use plastics.

Key Application Segments:

• Food packaging – Compostable films, containers
• Textiles – Sustainable apparel and biofibers
• Agriculture – Mulch films and nursery products
• Consumer goods – 3D printing, electronics, toys
• Medical – Sutures, implants, drug delivery materials

Key Growth Drivers

• Ban on petro-plastics and extended producer responsibility (EPR) policies
• Rising demand for compostable and recyclable polymers
• Abundance of biomass-derived sugars and organic acids
• Development of bio-based drop-in monomers (e.g., bio-BDO, bio-EG)
• Supportive green finance and ESG mandates

Challenges to Address

• Cost parity with fossil-based polyesters
• Feedstock price volatility and competition with food crops
• Performance tuning for mechanical/thermal properties
• Limited infrastructure for composting and recycling
• In India: Scale-up infrastructure and procurement policies are still evolving

Progress Indicators

• 2000–2005 – Commercialization of PLA by NatureWorks
• 2010 – First-generation bio-PET and PBS launched
• 2016 – Indian institutions begin pilot-scale PLA and PHA synthesis
• 2021 – Enzymatic bio-polyester synthesis under DBT programs
• 2024 – New polyester blends introduced with marine biodegradability

Most renewable polyester platforms are at TRL 8–9 globally, with multiple commercial offerings. In India, platforms range from TRL 5–7, with active R&D on monomer sourcing and enzymatic polymerization.

Conclusion

Biofabrication of renewable polyesters offers a scalable and sustainable solution to the plastic pollution crisis. With engineered microbes producing key monomers and bio-based processes enabling functional polymers, these materials support a low-carbon, circular economy.

India’s emerging biopolymer sector, backed by policy support and feedstock abundance, is well positioned to lead in bio-based material innovation, making renewable polyesters a viable and vital part of green manufacturing.

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