Ideonella sakaiensis: Plastic-Eating Bacteria for Bioremediation

Carbios has partnered with major companies to demonstrate industrial applications of enzymatic recycling. Michelin, the French tire manufacturer, plans to recycle PET bottles to produce high-tensile strength fibers for tire reinforcement. This application could recycle approximately 800,000 tons of PET annually, representing about 3 billion euros in value. The recycled fibers meet Michelin's quality requirements for tire components, demonstrating commercial viability. Carbios opened a demonstration plant in Lyon for testing and will build its first industrial plant in 2025, containing a reactor 20 times larger than current installations. The plant could recycle between 35,000 and 75,000 tons of PET annually. This represents a significant step toward implementing circular economy principles at industrial scale.

La biotecnología industrial aplica procesos biológicos para producir químicos, farmacéuticos, materiales y bioenergía de manera amigable con el medio ambiente. Los procesos fermentativos utilizan fuentes renovables como melaza, glucosa, almidón o aceites vegetales, transformándolas en energía y productos específicos (enzimas, antibióticos, vacunas) mediante sistemas biológicos. Los sistemas incluyen enzimas para biotransformación, terapias celulares con células vegetales o animales, bacterias con enzimas inmovilizadas, y virus para vacunas. El escalado de procesos sigue una secuencia: extracción de gen → clonación → inserción en sistema biológico → cultivo en matraces → reactor laboratorio → reactor piloto → reactor industrial, seguido de recuperación del producto y comercialización. Los biorreactores son el núcleo de un proceso biológico y deben diseñarse cuantitativamente basándose en características celulares: crecimiento y productividad. Deben proporcionar ambiente controlado con parámetros clave: pH, oxígeno disuelto, temperatura, agitación, alimentación, presión y nivel del tanque. Los biorreactores operan en cuatro modos principales: batch (sin entrada ni salida, volumen constante), fed-batch (entrada de nutrientes, control de inhibición), continuo (entrada y salida simultánea, estado estacionario), y perfusión (retención celular). Los tipos incluyen tanques agitados (más comunes, consumo energético alto), reactores air-lift (mezcla con aire, ideal para células sensibles), y reactores de lecho fluidizado (catalizadores inmovilizados, limitada transferencia de masa).

Industrial biotechnology scales genetic engineering for commercial production. Bioreactors are enclosed vessels maintaining optimal conditions: agitation systems mix cultures, oxygen delivery systems provide aeration, temperature/pH controls maintain conditions, and sampling ports enable monitoring. Types include stirred tanks (good mixing), air-lift systems (bubble circulation), and packed beds (cell immobilization). Downstream processing encompasses purification steps following biosynthesis: separation, purification, and formulation. This final stage ensures desired products meet quality standards for therapeutic or commercial use, often requiring months or years of processing time. Bioreactors enable large-scale production of pharmaceuticals, industrial chemicals, and agricultural products, transforming laboratory-scale genetic engineering into industrial manufacturing capabilities.

Bioreactors (बायोरिएक्टर) are vessels for large-scale production of biological products. They provide controlled conditions (temperature, pH, oxygen, nutrients) for cell growth and product formation. Stirred-tank bioreactors use rotating impellers to mix contents and ensure proper oxygen transfer. Applications include producing enzymes, vaccines, therapeutic proteins, and other biopharmaceuticals. The process involves: (1) cell culture in bioreactor, (2) product formation, (3) product harvesting, and (4) purification. Bioreactors enable industrial-scale production of biotechnology products.

PCR (Polymerase Chain Reaction), discovered by Kary Mullis, amplifies specific DNA sequences using DNA polymerase enzyme. The three-step thermal cycling process: (1) Denaturation at 95°C for 2 minutes breaks hydrogen bonds, separating double helix into single strands; (2) Annealing at 40°C allows single strands to serve as templates; (3) Extension/Elongation where DNA polymerase synthesizes complementary strands, doubling DNA with each cycle. Bioreactors are large vessels for commercial production of biological products like antibiotics and enzymes, providing optimal conditions (temperature, pH, nutrients, oxygen) for cultivating microorganisms, plant cells, or animal cells. The stirred tank bioreactor is most commonly used, capable of processing 100-1000 liters. Restriction enzymes (restriction endonucleases), discovered by Arber, are the most important enzymes in genetic engineering, also called molecular scissors. They cut DNA at specific palindromic recognition sequences and are produced by bacteria as defense mechanisms.

Current plastics recycling destroys material quality through high-temperature processes, preventing true circular economy. Amber Cycle developed biocycling using enzymes to convert post-consumer plastic into terephthalic acid and ethylene glycol—the building blocks of all plastics—through a closed-loop process operating at normal temperatures. This technology achieves what others cannot: simultaneous cost-effectiveness, post-consumer material use, and high-value product output. With the total PTA market at $50 billion annually, the startup targets 1.1% capture ($50 million) within seven years through direct sales and technology licensing.

Bio-upcycling is an innovative approach where specific bacteria, such as Ideonella sakaiensis discovered in Japan in 2001, use specialized enzymes to break down plastic polymers like PET into valuable monomers (terephthalic acid and ethylene glycol), which can then be converted into higher-value products or biodegradable plastics, offering a more sustainable alternative to traditional recycling methods that degrade plastic quality over time.

The bacterium Ideonella sakaiensis can degrade PET plastic by breaking it down into its monomers (terephthalic acid and ethylene glycol). The presenter explains that these monomers can then be used by the bacteria as carbon sources to produce ATP through cellular respiration. This represents a potential solution to plastic pollution, as the bacteria can use plastic as their sole carbon source. The presenter connects this to broader topics of biotechnology and environmental sustainability.

Monomers derived from PET breakdown were reconstructed to produce renewable polyester amides (PEAs) with excellent thermal properties, making them suitable for biomedical applications such as drug delivery and tissue engineering. Bisphenol A, while potentially damaging as an environmental pollutant, can be kept out of landfills and watercourses through this process. Dimethyl Carbonate serves as a valuable green solvent and building block for other industrial chemicals, enabling a circular economy where plastics remain in productive use indefinitely.

PETal is a synthetic biology project that uses engineered Pseudomonas putida bacteria to convert PET plastic waste monomers (terephthalic acid and ethylene glycol) into santalene and santalol, the key components of sandalwood oil, offering a sustainable alternative to traditional sandalwood extraction that reduces environmental strain on natural populations while addressing global plastic pollution.

Microbial degradation of polymers and acids: (1) Polystyrene - degraded by Vibrio bacteria, (2) Sulfuric acid - degraded by Acidophiles and Acidobacteria. These microorganisms help in breaking down synthetic materials and acidic environments.

Considering potential environmental hazards of synthetic polymeric waste, certain biodegradable synthetic polymers have been developed. These polymers contain functional groups similar to those in biopolymers such as wool, silk, and cellulose. Examples include: (1) Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) - formed by copolymerization of 3-hydroxybutanoic acid and 3-hydroxyvaleric acid, containing ester linkages in the repeating unit. PHBV is used for specialty packaging, medical sutures that don't need removal after surgery, and controlled drug release. (2) Nylon 6 - an alternating copolymer of glycine and caproic acid, formed by condensation reactions. (3) Polycaprolactone (PCL) - used for medical sutures, drug delivery, and specialty polyurethanes. (4) Poly(lactic acid) (PLA) - derived from plant-based materials (corn starch or sugar cane), used for packaging cups and takeout containers for cooled beverages, fiber for clothing, and medical applications like sutures and stents. Commercial composting facilities are needed to break down PLA, and it is more expensive than polyethylene terephthalate.

Polypropylene is a high-molecular-weight polymer from propylene polymerization at low/medium pressure and 80°C with catalysts, having molecular weight 80,000-200,000 and high crystallinity. It is more heat-resistant than polyethylene (up to 150°C), with stronger and more gas-impermeable films and elastic fibers. However, it has lower cold resistance (-10°C to -20°C). Copolymers combine properties of both materials. Polystyrene is a rigid, transparent polymer from styrene polymerization with high hardness, stiffness, and dielectric properties but decomposes above 200°C and is brittle at low temperatures. Polymethyl methacrylate (organic glass) is amorphous, transparent, resistant to dilute acids/alkalis, and operates from -60°C to +80°C, used for aircraft and automotive windows and optical lenses.

A fungus called Pestalotiopsis microspora, discovered in the Amazon rainforest by Yale researchers in 2011, can break down polyurethane plastic using enzymes like esterase and serarene hydrolase, working in anaerobic conditions without oxygen; however, scaling this technology for practical plastic waste management remains challenging due to slow degradation rates, potential ecological risks, and the need for safe byproduct management.

Synthetic rubbers include natural rubber (polyisoprene) strengthened by vulcanization (adding sulfur for cross-links), Buna-N (butadiene and acrylonitrile for oil resistance), Buna-S (butadiene and styrene for elasticity), and Neoprene (chloroprene for chemical resistance). Thermosetting polymers like Bakelite (phenol-formaldehyde resin) form rigid cross-linked networks that cannot be remelted, unlike thermoplastic polymers. Condensation polymers include Nylon 6,6 (hexanediamine and adipic acid with amide bonds), Nylon 6 (caprolactam through ring-opening), and Dacron (ethylene glycol and terephthalic acid with ester bonds). These have strong intermolecular forces making them durable for textiles and industrial applications. Polymers are classified by biodegradability: biodegradable (starch, cellulose, proteins) can be broken down by microorganisms, while non-biodegradable (polyethylene, polystyrene, teflon, bakelite) persist in the environment.