Scientists from the University of Edinburgh have devised a novel way of tackling the issue of plastic pollution by using bacteria to transform plastic waste into vanilla flavouring.

The researchers have discovered that the common bacteria E. coli can be deployed to convert post-consumer plastic into vanillin, which is the is the primary component of extracted vanilla beans and is responsible for the characteristic taste and smell of vanilla.

The world’s plastic crisis has seen an urgent need to develop new methods to recycle polyethylene terephthalate (PET), which is widely used for packaging. It is estimated that around 50  million tonnes of PET waste is produced annually, and while PET is recyclable, recycled products can also contribute to plastic pollution. 

To tackle this problem, scientists from the University of Edinburgh used lab engineered E. coli to transform terephthalic acid – a molecule derived from PET – into the high value compound vanillin, via a series of chemical reactions. The team also demonstrated how the technique works by converting a used plastic bottle into vanillin by adding the E. coli to the degraded plastic waste. Vanillin is widely used in the food and cosmetics industries, as well as the formulation of herbicides, antifoaming agents and cleaning products. Global demand for vanillin was in excess of 37,000 tonnes in 2018. 

Researchers say that the vanillin produced would be fit for human consumption but further experimental tests are required.

This is the first example of using a biological system to upcycle plastic waste into a valuable industrial chemical. “The results from our research have major implications for the field of plastic sustainability and demonstrate the power of synthetic biology to address real-world challenges," says Joanna Sadler, First author and BBSRC Discovery Fellow , School of Biological Sciences, University of Edinburgh.

"Our work challenges the perception of plastic being a problematic waste and instead demonstrates its use as a new carbon resource from which high value products can be obtained," adds Dr Stephen Wallace, Principle Investigator and UKRI Future Leaders Fellow, School of Biological Sciences, University of Edinburgh. 

"Using microbes to turn waste plastics, which are harmful to the environment, into an important commodity and platform molecule with broad applications in cosmetics and food is a beautiful demonstration of green chemistry, comments Dr Ellis Crawford. Publishing Editor at the Royal Society of Chemistry. 

The study, published in Green Chemistry lays the foundation for further studies to maximize vanillin production towards industrially relevant levels.