Uploaded July 2025 | Updated September 2026, 2 weeks ago
What is common to the soda bottles you drink from, the containers your berries come in, the sun-protection t-shirt you wear, the carpet you walk on, the blanket that marathoners wrap themselves in after a race and the video and audio tapes that entertained us before giving way to digital technology? They are all made of a plastic in the polyester family known as polyethylene terephthalate (PET). It is a “thermoplastic” polymer which means it can be melted and molded into different forms. A soda bottle, for example, starts out with the plastic molded into the shape of a test tube which is then placed in a bottle-shaped mold and inflated with air to take the shape of the mold.
The bottles collected by recyclers are melted down and converted into polyester fiber for clothing and carpets, strapping and non-food containers. Why not into beverage bottles? Because these must meet strict food-grade safety standards and the melted plastic can contain contaminants from labels, adhesives or other plastics that may have gotten into the mix. Generally selling the recycled plastic is less profitable than virgin plastic so there is extensive research into synthesizing more valuable substances from plastic waste.
One of the possibilities is converting post-consumer PET into vanillin, the primary component of the extract of vanilla beans that is responsible for the characteristic taste and smell of vanilla. Vanillin is also used in fragrance industry as well as a starting material for the production of pharmaceuticals, herbicides and cleaning products. Extraction from vanilla beans is expensive so there is a big market for synthetic vanillin. There are several synthetic approaches, but the most common one starts with lignin isolated from wood. Now researchers in Scotland have found a way to produce vanillin from PET waste.
The process begins by treating the plastic with an enzyme, “leaf-branch compost cutinase,” which as the term implies is isolated from composted leaves and branches. The enzyme degrades PET into its components, terephthalic acid and ethylene glycol. The terephthalic acid is then converted to vanillin by E. coli bacteria that have been genetically engineered to produce an enzyme that carries out this conversion. The same research group has also engineered E.coli to convert terephthalic acid into adipic acid, a chemical used to synthesize nylon. The current method of making adipic acid involves reaction of cyclohexanol with nitric acid, a process that is energy intensive and emits nitrous oxide, a potent greenhouse gas. It remains to be seen whether the production of vanillin and adipic acid from waste PET becomes financially viable, but if it does, it will provide further motivation for recycling this widely used plastic.
What is common to the soda bottles you drink from, the containers your berries come in, the sun-protection t-shirt you wear, the carpet you walk on, the blanket that marathoners wrap themselves in after a race and the video and audio tapes that entertained us before giving way to digital technology? They are all made of a plastic in the polyester family known as polyethylene terephthalate (PET). It is a “thermoplastic” polymer which means it can be melted and molded into different forms. A soda bottle, for example, starts out with the plastic molded into the shape of a test tube which is then placed in a bottle-shaped mold and inflated with air to take the shape of the mold.
The bottles collected by recyclers are melted down and converted into polyester fiber for clothing and carpets, strapping and non-food containers. Why not into beverage bottles? Because these must meet strict food-grade safety standards and the melted plastic can contain contaminants from labels, adhesives or other plastics that may have gotten into the mix. Generally selling the recycled plastic is less profitable than virgin plastic so there is extensive research into synthesizing more valuable substances from plastic waste.
One of the possibilities is converting post-consumer PET into vanillin, the primary component of the extract of vanilla beans that is responsible for the characteristic taste and smell of vanilla. Vanillin is also used in fragrance industry as well as a starting material for the production of pharmaceuticals, herbicides and cleaning products. Extraction from vanilla beans is expensive so there is a big market for synthetic vanillin. There are several synthetic approaches, but the most common one starts with lignin isolated from wood. Now researchers in Scotland have found a way to produce vanillin from PET waste.
The process begins by treating the plastic with an enzyme, “leaf-branch compost cutinase,” which as the term implies is isolated from composted leaves and branches. The enzyme degrades PET into its components, terephthalic acid and ethylene glycol. The terephthalic acid is then converted to vanillin by E. coli bacteria that have been genetically engineered to produce an enzyme that carries out this conversion. The same research group has also engineered E.coli to convert terephthalic acid into adipic acid, a chemical used to synthesize nylon. The current method of making adipic acid involves reaction of cyclohexanol with nitric acid, a process that is energy intensive and emits nitrous oxide, a potent greenhouse gas. It remains to be seen whether the production of vanillin and adipic acid from waste PET becomes financially viable, but if it does, it will provide further motivation for recycling this widely used plastic.
