Enzyme Engineering for Biobased Dicarboxylic Acids

Introduction

Dicarboxylic acids (DCAs) are essential platform chemicals used in polyesters, nylons, resins, adhesives, and pharmaceuticals. Common DCAs include adipic acid, succinic acid, itaconic acid, and muconic acid, which serve as the backbone for many synthetic polymers and materials.

While conventional production of these acids relies heavily on petrochemical oxidation routes, enzyme engineering enables their biosynthesis from sugars, glycerol, or lignocellulosic biomass. Through the design and optimization of highly specific, stable, and efficient enzymes, microbial hosts can be tuned for selective DCA production under mild and sustainable conditions.

What Products Are Produced?

• Adipic acid – Precursor for nylon 6,6
• Succinic acid – For biodegradable plastics, food additives
• Itaconic acid – Used in resins, adhesives, and coatings
• Muconic acid – Can be converted to terephthalic acid (bio-PET)
• Glutaric, malonic, pimelic acids – Specialty polymers and pharma uses

Pathways and Production Methods

1. Reductive TCA Cycle Pathways

• E. coli, Corynebacterium glutamicum engineered for succinic acid
• Utilizes pyruvate carboxylase, fumarase, and malate dehydrogenase
• Operates under anaerobic or CO₂-rich conditions

2. Polyketide and β-Oxidation Pathways

• Engineered microbial chassis for adipic acid and glutaric acid from glucose or muconate
• Employs monooxygenases, dehydrogenases, and ω-oxidases

3. Fungal Fermentation for Itaconic Acid

• Aspergillus terreus and engineered yeasts expressing cis-aconitate decarboxylase (CAD)
• Converts citric acid intermediates to itaconate

4. Shikimate-Derived Pathways for Muconic Acid

• Glucose → 3-dehydroshikimate → Catechol → Muconic acid
• Catalyzed by dehydratases, dioxygenases, and oxidases

Catalysts and Key Tools Used

Key Engineered Enzymes:

• Cis-aconitate decarboxylase (CAD) – for itaconic acid
• Muconate cycloisomerase and catechol dioxygenase – for muconate
• Aldehyde dehydrogenases – for terminal oxidation steps
• Succinic semialdehyde dehydrogenase – for succinate production

Enzyme Engineering Techniques:

• Directed evolution – improving substrate specificity and stability
• Site-directed mutagenesis – tuning active sites
• Enzyme fusion – to reduce intermediate loss
• Computational modeling – for structure-guided redesign

Microbial Hosts:

• E. coli, Yarrowia lipolytica, Corynebacterium glutamicum, Pseudomonas putida

Case Study: DuPont & Genomatica – Bio-Adipic Acid via Engineered Enzymes

Highlights

• Developed enzyme cascade for glucose → muconate → adipic acid
• Introduced cis,cis-muconate cycloisomerase and redox enzymes
• Used E. coli with high flux through shikimate and β-oxidation pathways
• Resulted in >90% selectivity, enabling downstream nylon production

Timeline

• 2014 – First demonstration of bio-adipic acid in engineered E. coli
• 2017 – Enzyme suite optimized for industrial fermentation
• 2021 – Tech transferred to pilot nylon-6,6 production line
• 2023 – Demonstrated 40% GHG reduction compared to fossil route

Global and Indian Startups Working in This Area

Global

• Genomatica (USA) – Adipic and malonic acid via microbial pathways
• BASF & Cargill – Succinic acid joint venture using engineered enzymes
• Verdezyne (USA) – Bio-adipic acid from palm oil waste
• Itaconix (UK) – Bio-itaconic acid polymers for consumer goods

India

• IISc Bangalore – Metabolic modeling of itaconic acid synthesis
• CSIR-NCL Pune – Enzyme engineering for succinic and muconic acid
• Godavari Biorefineries – Fermentation-based succinic acid
• Startups via BIRAC – Developing bio-nylon precursors and adhesives

Market and Demand

The global dicarboxylic acid market was valued at USD 6.5 billion (2023), projected to reach USD 10.8 billion by 2030, at a CAGR of ~7.4%.

Major End-Use Segments:

• Polyamides and polyesters – Nylon, PET alternatives
• Biodegradable plastics – PGA, PBS, PEF
• Adhesives and resins – Acrylic and unsaturated polyester resins
• Cosmetics and pharmaceuticals – Buffering agents, excipients

Key Growth Drivers

• Growing need for bio-based polymers and packaging
• Carbon-neutral manufacturing mandates
• Advances in enzyme optimization and synthetic biology
• Compatibility with lignocellulosic feedstocks
• Corporate interest in green nylon and biopolyesters

Challenges to Address

• Enzyme stability under industrial conditions
• Low pathway flux and product inhibition
• Co-factor imbalances in redox-sensitive reactions
• Product recovery from fermentation broth (especially itaconate and muconate)
• India-specific: Lack of end-use industries for niche DCAs

Progress Indicators

• 2013 – Engineered CAD enzymes for itaconic acid
• 2016 – First full pathway for adipic acid in E. coli
• 2019 – India begins metabolic modeling for DCA pathways
• 2022 – Enzyme libraries for muconate and succinate expanded
• 2024 – Indian trials on bio-based adhesives and PEF precursors using DCAs

Enzyme-based microbial production of dicarboxylic acids is at TRL 7–8 globally; in India, TRL 5–6, with several pilot-scale enzyme engineering and fermentation systems in place.

Conclusion

The enzyme engineering of microbial systems for dicarboxylic acid production is ushering in a new era of precision fermentation and green polymer chemistry. As industries seek renewable solutions for nylon, polyester, and specialty polymers, these bio-based DCAs are becoming essential molecular building blocks.

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