Researchers from Israel-based Ben Gurion University are looking into bio-degradation by bacteria in collaboration with Portuguese company Ecoibéria. Their objective is to find a simpler and more sustainable method to recycle polyethylene terephthalate (PET).
‘Our research deals with the decomposition of various polymers of plastics,’ says Prof. Ariel Kushmaro of BGU’s department of biotechnology engineering. His crew was successful; they discovered several types of bacteria capable of successfully biodegrading polyethylene microplastics in soil samples.
Kushmaro explains that it’s possible to break down organic matter––carbon chains, like sugars and even proteins. A big challenge is that PET is a non-biodegradable substance owing to its highly stable carbon-carbon bonds.
‘We thought because plastic, polyethylene, and PET were also made up of carbon chains, we would prepare a kind of ‘enrichment culture’––soil that was contaminated over the years with plastic or PET with its original bacterial population,’ he tells news company Israel 21c.
Along with the bacteria, the researchers added the material that they wanted them to break down and let the material sit for a few weeks. After several attempts, we the team witnessed a microorganism that grows and utilises polyethylene as a carbon and energy source. ‘These are the bacteria that can handle the polymers,’ Kushmaro says.
‘We understood that in order for the bacteria to bio-degrade the carbon bonds in the plastic polymers, it had to be grown in a carbon-free environment, so that the bacteria had no other choice but to consume the only available carbon in the plastic to survive.’
The researcher adds: ‘Of course, for the purpose of the process it is not enough to just supply the bacteria with carbon chains. We had to give them all kinds of additives, like sources of nitrogen and phosphorus to make it easier for them to perform decomposition.’
‘We found that within 30 days, 10% to 20% of the soil’s weight was lost just through the decomposition activity performed by the bacteria, which emitted carbon dioxide in the process of respiration,’ Kushmaro reveals.
And he concludes: ‘Plastic-containing products is one of the toughest environmental challenges facing modern society. Existing technologies, such as thermo-mechanical recycling impair the mechanical properties of the polymer and suffer from other disadvantages such as the need for organic solvents, high reaction temperatures and intensive waste sorting. Bacterial degradation of PET into recyclable materials that can be then reused to manufacture new PET products, is therefore a promising strategy that can have a global environmental and economic impact.’
Ecoibéria, which is based in the north of Portugal and was founded in 2005, curently owns a 17 000 m2 site where it processes around 50 000 tonnes of PET waste every year.
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