Introduction

Polyurethanes (PUs) are versatile polymers widely used in foams, coatings, elastomers, adhesives, and sealants, forming an integral part of industries like automotive, construction, and furniture. Traditionally, PU synthesis involves fossil-derived polyols and isocyanates, particularly from petrochemicals like propylene oxide, toluene diisocyanate (TDI), and methylene diphenyl diisocyanate (MDI), all of which pose toxicity and environmental concerns.

The biobased alternative lies in engineering microbial pathways to produce renewable polyol and isocyanate precursors from sugars, glycerol, fatty acids, or lignocellulosic biomass. By harnessing microbial fermentation and enzyme-catalyzed transformations, scientists aim to build a non-toxic, low-carbon route for the production of PU precursors, enabling circular and sustainable polyurethanes.

What Products Are Produced?

Biobased Polyols (hydroxyl-functional monomers):

• 1,3-propanediol (PDO)
• Glycerol derivatives
• Sugar alcohols (sorbitol, xylitol)
• Fatty-acid based polyols

Biobased Isocyanate Precursors:

• Lysine-derived diisocyanates (LDI)
• Furfuryl alcohol-based isocyanates
• Non-isocyanate polyurethanes (NIPUs) using cyclic carbonates + amines

Pathways and Production Methods

1. Polyol Biosynthesis

• 1,3-Propanediol (PDO): via engineered E. coli or Clostridium species from glycerol
• Sorbitol, Xylitol: via hydrogenation of glucose and xylose
• Glycerol Derivatives: modified through epoxidation and ring opening
• Fatty Acid-Based Polyols: via microbial ω-oxidation followed by reduction

2. Isocyanate Alternatives via Amino Acid Derivatives

• L-Lysine fermentation → decarboxylation → lysine diisocyanate (LDI)
• Furfuryl alcohol from hemicellulose hydrolysate → nitration or oxidation to produce isocyanate-like compounds

3. Non-Isocyanate Polyurethanes (NIPUs)

• CO₂ + epoxides → cyclic carbonates
• Reaction with bio-based amines → polyurethane linkages without isocyanates

Catalysts and Key Tools Used

Engineered Microorganisms:

• E. coli, Klebsiella pneumoniae, Clostridium butyricum – PDO from glycerol
• Yarrowia lipolytica, Pseudomonas putida – Fatty acid polyol derivatives
• Corynebacterium glutamicum – Fermentative lysine production

Key Enzymes:

• Glycerol dehydratase, 1,3-propanediol oxidoreductase
• Aminotransferases, decarboxylases, lipoxygenases
• Epoxide hydrolases for NIPU routes

Fermentation Technologies:

• Fed-batch bioreactors for high-titer polyols
• In situ separation techniques to reduce product inhibition
• Solvent-free post-polymerization under mild conditions

Case Study: Covestro (Germany) – Bio-based Polyols and Isocyanate Alternatives

Highlights

• Developed bio-PDO and sugar-based polyols for flexible foams
• Worked on non-isocyanate PU (NIPU) using cyclic carbonates from CO₂
• Targeted markets: footwear, automotive seats, insulation foams
• Collaborated with Genomatica for microbial production of key monomers

Timeline

• 2013 – Start of biobased polyol development
• 2017 – Pilot-scale production of sugar-based polyols
• 2021 – Launch of NIPU for low-VOC coatings
• 2024 – Ongoing expansion into circular foam recovery

Global and Indian Startups Working in This Area

Global

• Genomatica (USA) – Bio-PDO, bio-BDO platform molecules for PUs
• Covestro (Germany) – Biobased polyols and isocyanate alternatives
• Novomer (USA) – CO₂-based cyclic carbonates for NIPUs
• BASF (Germany) – Polyurethane innovation from biosynthetic diols

India

• Godavari Biorefineries – Working on sorbitol and sugar-alcohol polyols
• CSIR-IICT, NCL Pune – Fermentation of glycerol to PDO
• IIT Madras, ICT Mumbai – Process integration for bio-polyol scale-up
• Early-stage BIRAC-supported startups – Focused on PU foam alternatives from agro-waste

Market and Demand

The global polyurethane market reached USD 78 billion in 2023, with the biobased segment growing at ~9–10% CAGR, driven by demand in green building materials, automotive interiors, and packaging.

Major End-Use Segments:

• Flexible and rigid foams – Mattresses, furniture, insulation
• Coatings and adhesives – Construction, automotive, electronics
• Footwear and sports gear
• Elastomers and fibers

Key Growth Drivers

• Push for low-VOC, low-carbon materials in construction and furniture
• Increasing availability of glycerol and sugar derivatives
• Demand for non-toxic, isocyanate-free PU systems
• CO₂ capture utilization in cyclic carbonate-based NIPUs
• Government incentives for bio-based building materials and circular polymers

Challenges to Address

• Yield optimization for microbial polyol production
• High viscosity and processing issues of some biobased precursors
• Scale-up bottlenecks in non-isocyanate PU polymerization
• Cost competitiveness with established petrochemical PUs
• Regulatory approval for new PU compositions in sensitive applications

Progress Indicators

• 2008 – Bio-PDO reaches pilot scale from glycerol
• 2014 – NIPU systems developed using CO₂-derived intermediates
• 2020 – Commercial launch of bio-polyols for automotive and footwear
• 2023 – Indian institutes develop microbial PDO >70 g/L titers
• 2025 (ongoing) – Industrial trials of NIPUs in packaging and foam insulation

Microbial production of polyol precursors is at TRL 8–9 globally, with commercial PU products in the market. In India, it is at TRL 5–6, with fermentation optimization and polymer R&D ongoing.

Conclusion

The biotechnological route to biobased polyurethane precursors offers a powerful alternative to petrochemical plastics, enabling flexible, durable, and environmentally friendly foams, coatings, and adhesives. With advances in microbial fermentation, enzyme catalysis, and green polymerization, this domain is rapidly converging toward a sustainable and circular materials economy.

India’s bioeconomy goals can benefit immensely by integrating biopolyol fermentation with domestic polymer industries, opening up a future of renewable, recyclable polyurethane products.

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