Researchers Discovered Microbes Like Ideonella Sakaiensis

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Since its discovery in 2016, the bacterium Ideonella sakaiensis has been a subject of ongoing research for its ability to naturally break down PET plastic. Recent news covers advanced genetic engineering to improve its enzymes, new findings on its degradation process, and efforts to scale the technology for industrial use, including breaking down microplastics in marine environments.

Recent News and Advancements

 Engineering for enhanced efficiency

• Faster, more stable enzymes: Researchers have genetically engineered mutant versions of the PET-degrading enzymes, PETase and MHETase, to function more efficiently and at higher temperatures. One mutant, for example, showed a 3.3-fold increase in activity on highly crystalline PET, the type used for most plastic bottles.
• Tandem enzyme action: A French biotechnology company, Carbios, has created a “super-enzyme” that combines the functions of PETase and MHETase. This engineered enzyme can break down 90% of a PET bottle in just 10 hours, a drastic improvement over the original bacteria.
• Modified marine bacteria: In 2023, scientists successfully genetically modified a fast-growing marine microbe, Vibrio natriegens, to produce the PET-degrading enzymes from I. sakaiensis. This advancement allows for PET to be broken down in saltwater at room temperature, offering a potential solution for ocean plastic pollution.

Bio-upcycling and the circular economy

• Converting plastic to bioplastics: News from 2021 reported that I. sakaiensis can not only break down PET but also convert it into biodegradable bioplastics, such as poly(3-hydroxybutyrate) (PHB). This process offers a sustainable pathway for recycling problematic plastics and creating valuable, eco-friendly materials.
• Producing renewable monomers: The enzymes break down PET into its original building blocks terephthalic acid (TPA) and ethylene glycol (EG). These monomers can be purified and used to produce new PET, allowing for an efficient closed-loop recycling system.

Environmental applications

• Addressing microplastics: Research is underway to develop microbial systems that can target and remove microplastics and nanoplastics from soil and water. The modified marine bacteria are a crucial step toward addressing the widespread microplastic problem in oceans.
• Wastewater treatment: The bacteria show promise for breaking down plastic waste in sewage and wastewater treatment facilities, potentially using its abilities to degrade PET in fisheries without harming fish populations.

Challenges and limitations

Despite the promising progress, several hurdles remain for widespread, industrial application:

• Slow degradation rate: While genetically enhanced enzymes work much faster than the natural bacteria, the process is still too slow for many large-scale industrial applications.
• Cost of scalability: The cost of manufacturing and deploying engineered enzymes or microbes at an industrial scale remains a significant challenge compared to conventional recycling and incineration.
• Environmental release concerns: The prospect of releasing genetically engineered organisms into the natural ecosystem raises ethical and regulatory concerns. Further research is needed to understand the long-term ecological impact.
• Variable plastic composition: Standard PET bottles are highly crystalline, which is more difficult for enzymes to break down than amorphous PET. Additionally, I. sakaiensis only targets PET, leaving other common plastics untouched, though other plastic-degrading organisms are also being investigated.