Plastics

• Only 9% of the plastic ever made has been recycled
• Over 12 million metric tonnes of plastic enter the ocean every year, on top of the 362 million metric tonnes already there
• Plastic waste is 80% of all marine debris and causes major health issues for marine life
• Microplastics break off of larger plastic items and enter the food chain
• Most plastic does not biodegrade and can last for hundreds of years in the environment
• Ideonella sakaiensis


  Bacteria discovered in Japan that can break down PET plastic
• PET plastic


  Polyethylene terephthalate, a common type of plastic used for water bottles and food packaging
• Monomer


  Repeated unit that makes up a polymer
• Polymer


  Long chain of monomers
• PETase


  Enzyme produced by Ideonella sakaiensis that can break down the bonds between PET monomers
• Monomers


  Molecular building blocks that make up proteins
• Plastic


  • Tough and durable
  • Remains in the environment for a long time
  • Natural processes can only break it into smaller pieces but cannot break polymer chains apart
• Ideonella sakaiensis


  Bacteria that can break down the bonds between monomers using enzymes
• Enzymes


  Speed up the chemical reactions that take place in cells
• Digestive enzymes


  Break down larger molecules into smaller ones that can be absorbed by bacteria
• PETase


  Enzyme produced by Ideonella sakaiensis that breaks down the bonds in the polymer to form monomers
• There is an awful lot of plastic waste, with 8.3 billion Mt produced historically, 79% of which has gone into landfills or the environment
• It would be hard to make enough bacteria to eat all the plastic waste
• Bacteria digest plastic very slowly
• Speeding up plastic digestion by bacteria

  1. Researchers engineered PETase to break down bottles in days rather than months

  2. Researchers combined PETase with another enzyme to create a 'super-enzyme' that works 6 times faster
• Swiss scientists found bacteria that can digest some types of plastic in colder temperatures, down to 4°C
• Bacteria can only break down a few specific types of plastic, e.g. PETase can only break down PET plastic, and cold-temperature bacteria can only break down biodegradable plastics like polyester-polyurethane (PUR)
• Bacteria produce waste in the form of small monomers that can be recycled into new plastic objects