Heat and bacteria recycle mixed plastics into useful chemicals, but scaling the process is unresolved

Good news! We are making more progress in the recycling/waste management of plastics! Human ingenuity at its best! It is only a matter of time and resources to address the issue of plastic waste!

Plastophobia be gone! 😊

"... A team ... has developed a two-step process that uses chemistry and then biology to break down a mix of the most common plastics that make it into recycling plants: high-density polyethylene (HDPE), ... and polyethylene terephthalate (PET) ...

“Only a few works have reported chemical recycling of plastic mixtures before,”... “Combining chemical and biological pathways to convert plastic mixture is even more rare,” ...

The team first used a catalysed oxygenation reaction, with a cobalt or manganese-based catalyst, to break down the tough polymer chains into oxygen-containing organic-acid molecules. ...

to turn the organic-acid molecules into something more easily commoditized. To do that, the team turned to microbes — specifically, the bacterium Pseudomonas putida, which can be engineered to use different small organic molecules as a source of carbon. ... The team engineered the microoorganisms to consume the oxygenated organic molecules that the researchers made from the different plastics using their ‘autoxidation’ reaction: dicarboxylic acids from polyethylene, teraphthalic acid from PET and benzoic acid from polystyrene.

The bacteria produced two chemical ingredients that are each used to make high-quality performance-enhanced polymers or biopolymers. ..."

From the editor's note:

"Current plastic recycling methods require sorting by chemical composition, a method that is expensive and results in products that are of lower quality and value than the starting plastic. If plastic waste could instead be converted to valuable chemical intermediates, then economical use of mixed waste as a feedstock might be feasible. Sullivan et al. developed a two-stage oxidation and biological funneling approach that can break down and reform mixtures of common consumer plastics (see the Perspective by Yan). The end products can be adjusted by metabolic engineering of the microbes in the second step, which should enable tailored conversion into various platform or specialty chemicals."

From the abstract:

"Mixed plastics waste represents an abundant and largely untapped feedstock for the production of valuable products. The chemical diversity and complexity of these materials, however, present major barriers to realizing this opportunity. In this work, we show that metal-catalyzed autoxidation depolymerizes comingled polymers into a mixture of oxygenated small molecules that are advantaged substrates for biological conversion. We engineer a robust soil bacterium, Pseudomonas putida, to funnel these oxygenated compounds into a single exemplary chemical product, either β-ketoadipate or polyhydroxyalkanoates. This hybrid process establishes a strategy for the selective conversion of mixed plastics waste into useful chemical products."

Heat and bacteria recycle mixed plastics into useful chemicals Two-step process converts mixtures of plastic into small molecules, but could be challenging to implement at scale.

Mixed plastics waste valorization through tandem chemical oxidation and biological funneling (no public access despite that one of the senior authors is an employee of a U.S. federal laboratory???)