Biosynthesis of Biobased Isoprene via Engineered Bacteria

Introduction

Isoprene (C₅H₈) is a volatile hydrocarbon and a key monomer used primarily in the production of synthetic rubber, especially polyisoprene and styrene-isoprene-styrene (SIS) copolymers. It is also used in adhesives, specialty elastomers, and medical equipment. Currently, isoprene is derived from naphtha cracking, a fossil-dependent and emission-intensive process.

To reduce environmental impact and enable renewable supply, researchers have turned to the biosynthesis of isoprene using engineered bacteria. Through metabolic engineering of microbes like E. coli, Bacillus subtilis, and Synechocystis, isoprene can be synthesized from sugars or CO₂, offering a sustainable and scalable alternative to petroleum-derived isoprene.

What Products Are Produced?

Biobased Isoprene

• Primary use in synthetic rubber (e.g., polyisoprene tires)
• Specialty elastomers for adhesives, footwear, coatings
• Medical-grade latex and sealing compounds

Pathways and Production Methods

1. MEP Pathway (Methylerythritol Phosphate Pathway)

• Native to many bacteria and cyanobacteria
• Glucose → Pyruvate + G3P → IPP/DMAPP → Isoprene via isoprene synthase

2. MVA Pathway (Mevalonate Pathway)

• Introduced into E. coli or B. subtilis
• Acetyl-CoA → HMG-CoA → Mevalonate → IPP/DMAPP → Isoprene

→ Isoprene synthase (ispS) converts dimethylallyl pyrophosphate (DMAPP) to isoprene in both pathways

3. CO₂ Fixation via Cyanobacteria

• Synechocystis and Synechococcus engineered to produce isoprene using photosynthesis
• Offers direct CO₂-to-isoprene conversion, ideal for climate-positive solutions

Catalysts and Key Tools Used

Engineered Microbes:

• E. coli, Bacillus subtilis – Heterologous MVA pathway
• Synechocystis, Synechococcus elongatus – Native MEP pathway with ispS
• Corynebacterium glutamicum – High-yield aerobic production

Key Enzymes:

• Isoprene synthase (ispS) – Converts DMAPP → isoprene
• HMG-CoA reductase, mevalonate kinase – MVA pathway control
• DXS, DXR, IspG – MEP pathway enhancements
• Efflux pumps and gas-permeable membranes – For isoprene removal

Fermentation Platforms:

• Gas-stripping bioreactors for isoprene collection
• Fed-batch glucose or glycerol fermentation
• Photobioreactors for CO₂-based systems

Case Study: Goodyear + Genencor (DuPont) – Bio-Isoprene from E. coli

Highlights

• Developed engineered E. coli expressing full MVA pathway and ispS
• Produced bio-isoprene from glucose at pilot scale
• Used for tire-grade polyisoprene in Goodyear’s concept tires
• Reduced dependency on fossil naphtha and minimized VOC emissions

Timeline

• 2008 – Goodyear–Genencor collaboration initiated
• 2012 – Pilot-scale demonstration of bio-isoprene
• 2015 – First bio-isoprene tires showcased
• 2023 – Ongoing scale-up and integration into green tire R&D

Global and Indian Startups Working in This Area

Global

• Amyris (USA) – MVA pathway development for terpenoid and isoprene production
• Genencor/DuPont (USA) – Early leader in engineered E. coli for bio-isoprene
• Goodyear (USA) – Collaborated on tire-grade polyisoprene
• Evonik and DSM – Working on MEP pathway optimization in Corynebacterium

India

• IIT Delhi, CSIR-NCL – Engineered microbes for IPP/DMAPP pathway extension
• ICT Mumbai – Studies on terpene biosynthesis using sugar feedstocks
• BIRAC-funded startups – Exploring bio-isoprene for specialty elastomers
• Private sector (e.g., Reliance R&D) – Interested in integrating into synthetic rubber value chain

Market and Demand

The global isoprene market stood at USD 4.2 billion in 2023, projected to reach USD 6.1 billion by 2030, with a CAGR of ~5.5%. Biobased isoprene is expected to capture up to 15% of the market by 2030, driven by sustainability mandates and green tire initiatives.

Major End-Use Segments:

• Synthetic rubber – Tires, belts, footwear
• Adhesives and sealants
• Medical gloves and tubing
• Pressure-sensitive tapes and coatings

Key Growth Drivers

• Demand for green tires and sustainable elastomers
• Abundant sugar and lignocellulosic feedstocks
• Advancements in terpenoid biosynthesis pathways
• Carbon-reduction goals of automotive and packaging sectors
• Integration potential with photosynthetic CO₂ capture systems

Challenges to Address

• Volatility and toxicity of isoprene to host microbes
• Gas-stripping and capture systems need cost-effective scaling
• Balance between growth and isoprene production (metabolic burden)
• Scale-up fermentation economics versus naphtha cracking
• Regulation for high-purity isoprene use in medical-grade materials

Progress Indicators

• 2009 – MVA pathway introduced in E. coli for isoprene
• 2013 – Cyanobacteria produce isoprene directly from CO₂
• 2015 – Bio-isoprene tires publicly demonstrated
• 2020 – Pilot plants running 24/7 for bio-isoprene trials
• 2024 – Indian labs report isoprene titers of ~2 g/L using MEP engineering

Biobased isoprene production is at TRL 7–8 globally, with pilot to early commercial demonstration; in India, it stands at TRL 4–6, with academic and industry-led pilot efforts in progress.

Conclusion

The biosynthesis of isoprene via engineered bacteria marks a crucial shift in the rubber and elastomer industry, aligning performance with sustainability. With advances in metabolic pathway optimization, gas fermentation systems, and host strain engineering, bio-isoprene can now viably compete with fossil-derived alternatives.

As India builds capabilities in bio-industrial platforms and renewable chemistry, bio-isoprene offers strategic value in enabling a green automotive future, circular material economy, and reduced petrochemical dependency.

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