Enzymatic Synthesis of Biobased Acrylic Acid

Introduction

Acrylic acid is a vital monomer used in superabsorbent polymers (SAPs), paints, adhesives, coatings, and textiles. The global demand for acrylic acid is rapidly growing, but its current production relies heavily on fossil-derived propylene through high-temperature oxidation, which is both energy-intensive and environmentally harmful.

To shift toward greener alternatives, researchers have developed routes for the enzymatic synthesis of biobased acrylic acid—a cleaner and renewable method using biomass-derived intermediates like glycerol or 3-hydroxypropionic acid (3-HP). By combining metabolic engineering, enzymatic cascades, and green chemistry, this approach opens a path to producing acrylic acid from sugars, waste glycerol, and lignocellulose, while reducing carbon emissions and hazardous by-products.

What Products Are Produced?

Acrylic Acid (AA) – Used in:

• Superabsorbent polymers (SAPs) – Diapers, hygiene products
• Adhesives and sealants
• Paints and coatings
• Textile treatments and dispersants

Derivatives:

• Acrylate esters – Methyl acrylate, ethyl acrylate
• Polyacrylates – Used in plastics, elastomers, and water treatment

Pathways and Production Methods

1. Biological Route via 3-Hydroxypropionic Acid (3-HP)

• Sugar → Glycerol → 3-HP → Acrylic Acid
• 3-HP is produced via engineered microbes and then dehydrated enzymatically or chemically to acrylic acid

2. Enzymatic Cascade Systems

• Use of glycerol dehydratase, aldehyde dehydrogenase, and 3-HP dehydratase
• Avoids harsh chemicals and extreme temperatures used in conventional catalysis

3. Alternative Routes

• From lactic acid: microbial fermentation followed by enzymatic or chemoenzymatic decarboxylation
• From acrylonitrile precursors using engineered nitrile hydratases (less common)

Catalysts and Key Tools Used

Key Enzymes:

• Glycerol dehydratase – Converts glycerol to 3-hydroxypropionaldehyde
• Aldehyde dehydrogenase – Converts aldehyde to 3-HP
• 3-HP dehydratase – Converts 3-HP to acrylic acid
• Carboxylic acid reductase (CAR) – For advanced biocatalysis pathways

Engineered Microorganisms:

• Klebsiella pneumoniae, E. coli, Halomonas – For 3-HP production
• Pichia pastoris – Recombinant protein expression for enzyme cascades
• Corynebacterium glutamicum – For redox-balanced conversions

Reaction Conditions:

• Mild temperature and pH (25–45°C, pH 6–8)
• Avoidance of heavy metals and oxidants
• Continuous bioreactor systems with co-factor recycling (e.g., NAD⁺/NADH)

Case Study: Cargill + Novozymes – Acrylic Acid via Enzymatic Glycerol Pathway

Highlights

• Developed an enzyme cascade for converting renewable glycerol to acrylic acid
• Produced 3-HP via engineered E. coli and dehydrated enzymatically to acrylic acid
• Aimed to replace propylene-based AA in superabsorbents and coatings
• Demonstrated reduced CO₂ emissions by 60–70%

Timeline

• 2010 – Enzyme screening and 3-HP pathway engineering begins
• 2014 – Pilot-scale trials of enzymatic 3-HP to AA conversion
• 2017 – Full cascade process validated at demonstration scale
• 2022 – Integrated with downstream SAP manufacturers for field deployment

Global and Indian Startups Working in This Area

Global

• Cargill + Novozymes (USA/Denmark) – Leaders in biobased AA via enzymatic glycerol pathway
• BASF (Germany) – Evaluating 3-HP enzymatic routes for acrylic acid
• ADM (USA) – Exploring lactic acid to AA via microbial platforms
• METabolic EXplorer (France) – Focused on biobased intermediate (3-HP) production

India

• CSIR-IIP & CSIR-NCL – Investigating 3-HP and enzymatic dehydration for AA
• IIT Delhi & ICT Mumbai – Working on enzyme discovery for acrylic acid synthesis
• Godavari Biorefineries – Exploring downstream integration of glycerol valorization
• Startups under BIRAC-BIG grants – Active in enzyme cascade development and glycerol upcycling

Market and Demand

The global acrylic acid market was valued at USD 13.4 billion in 2023, and is expected to reach USD 18.2 billion by 2030, growing at a CAGR of ~4.5%. The biobased segment is poised for higher growth (~8–9%) driven by demand for green SAPs and low-carbon adhesives.

Major End-Use Segments:

• Superabsorbent polymers – Diapers, adult care, medical pads
• Coatings and paints – Eco-friendly formulations
• Adhesives and sealants – Packaging and construction
• Textile and water treatment polymers

Key Growth Drivers

• High environmental impact of petrochemical acrylic acid
• Surge in demand for biodegradable and green personal care products
• Drop-in compatibility of biobased acrylic acid in existing value chains
• Availability of waste glycerol from biodiesel plants
• Advances in enzyme discovery, expression, and process integration

Challenges to Address

• Enzyme stability under industrial conditions (pH, temperature, substrate load)
• 3-HP dehydration bottlenecks – Yield and selectivity issues
• Process integration between fermentation and enzymatic steps
• High purification cost of acrylic acid due to co-products
• Need for continuous cofactor regeneration systems (NAD⁺/ATP)

Progress Indicators

• 2008 – 3-HP to AA route proposed as green alternative
• 2014 – Enzyme cascade developed and validated by Cargill
• 2019 – Pilot production achieves over 80% yield conversion
• 2022 – Startups in India begin enzyme screening programs
• 2024 – Commercial discussions for biobased SAPs in Asia-Pacific market

The enzymatic production of acrylic acid from biomass is currently at TRL 6–7 globally, with demonstration-scale trials ongoing, and at TRL 4–5 in India, focused on enzyme screening and cascade optimization.

Conclusion

The enzymatic synthesis of biobased acrylic acid presents a cleaner, modular alternative to fossil-based production. It integrates green feedstocks, low-energy processes, and tailored enzyme cascades, making it highly attractive for future sustainable polymer markets.

As India invests in biocatalysis, glycerol valorization, and bio-based materials, enzymatic acrylic acid production could become a strategic industry, enabling the shift toward non-toxic, biodegradable, and circular consumer products.

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