Scientists working on plastic waste solutions have developed a two-step chemical and biological process to break down mixed plastics and upcycle them into valuable bio-products.
The multi-agency project will utilize the synthetic biology expertise of the Department of Energy’s Oak Ridge National Laboratory to design microbes that will convert deconstructed plastic waste into building blocks for next-generation materials. increase.
A new process described in the journal chemistry, It replaces current systems that require laborious and costly sorting of materials, resulting in only about 5% of plastic being recycled in the United States.
Led by the National Renewable Energy Laboratory, the project brings together scientists from the Massachusetts Institute of Technology, the University of Wisconsin-Madison, and ORNL to keep thermoplastics out of landfills and the environment under biooptimization techniques. BOTTLE consortium.
Different plastics contain different polymers, each with their own chemical building blocks. BOTTLE researchers developed a process to convert mixed plastics into a single chemical product, with the goal of a solution that would allow recyclers to skip sorting.
The first step in the process relies on oxygen and a catalyst to break down large polymer molecules into smaller chemical building blocks. This process was applied to three common plastic mixtures used in disposable coffee cups. Polyethylene terephthalate (PET) used in disposable beverage bottles, polyester clothing and carpets. High density polyethylene (HDPE) is used in many common consumer plastics and is often used in milk jugs.
Greg Beckham, Senior Research Fellow at NREL and Director of BOTTLE, said:
Oxidation processes break these plastics down into a complex mixture of chemical compounds (benzoic acid, terephthalic acid, dicarboxylic acids, etc.). A sophisticated and costly separation is required to obtain a pure product. That’s where biology comes in.
BOTTLE colleagues manipulated soil microbes, Pseudomonas putida, which biologically transforms or “funnels” a mixture of small-molecule intermediates into a single product. Either polyhydroxyalkanoates or PHAs, an emerging form of biodegradable bioplastic. Or beta-ketoadipate can be used to make new nylon materials with better performance.
This experiment builds on a process developed by Adam Guss at ORNL and colleagues at NREL to engineer bacteria with desirable traits from other organisms.Process outlined in the journal metabolic engineeringconverted decomposed PET into building blocks to produce superior water and heat resistant nylon products ideal for applications such as automotive parts.
“We took a combinatorial approach to pathway building, essentially finding the best combination of genes from different organisms to ensure PET availability. Pseudomonas putida‘ said Gus. “ORNL specializes in modifying non-model microorganisms to add useful properties to biotechnology, leveraging our deep expertise in synthetic biology, transcriptomics and proteomics to discover new metabolic pathways. I have.”
“Biofunneling means that the metabolic network of microorganisms has been manipulated to direct carbon from many substrates to a single product. chemistry paper. “To do this, we take DNA from nature (usually other microorganisms) and Pseudomonas putidais the genome of DNA is transcribed into RNA, which is then translated into proteins that perform a variety of biochemical transformations, forming new metabolic networks, ultimately allowing more carbon to be captured and regulated where it goes. increase. “
Guss and colleagues spent years perfecting p. putida As part of DOE’s Bioenergy Innovation Center and Agile Biofoundry, we transform plant biopolymer lignin derived from bioenergy crops into advanced bioproducts. In 2020, Guss led a team that announced they had engineered microbes to simultaneously digest five of his biomass’s most abundant compounds, lignocellulose.
BOTTLE’s next step states: p. putida We’re working to break down more types of plastics and more real-world plastics with additional additives so you can eat them.
“Plastic is a major environmental pollutant and is primarily made using fossil carbon,” he said. “This research sits at the crossroads of breaking down today’s plastic waste and transforming it into next-generation plastic building blocks that are both recyclable and biodegradable by design.”
