Scientists have genetically engineered bacteria to efficiently turn plastic waste into useful chemicals.
The bacteria, described in a study published in the journal Nature Communications, could help tackle the growing problem of plastic pollution, the authors said.
“Plastic pollution is an escalating global crisis, with a staggering 390 million tons of plastic produced annually worldwide,” two of the study authors, James Collins from MIT and Ting Lu with the University of Illinois Urbana-Champaign, told Newsweek.
“Shockingly, a whopping 91 percent of this plastic finds its way into incineration or landfills, exacerbating the environmental, wildlife, and human health issues stemming from plastic pollution,” Lu and Collins said.
Recent History of Upcycling Plastics with Microogranisms
In recent years, one potential solution for upcycling plastics has emerged, using specially engineered microorganisms to turn the waste into useful products. While this approach offers some promise in contrast to conventional plastic waste processing methods, it is highly complex and beset with difficulties.
To date, this approach has predominantly revolved around using single populations or strains of microorganisms, commonly called monocultures.
Despite notable advancements, the monoculture strategy encounters several challenges, including inefficiencies and incompleteness when it comes to the degradation of plastic and difficulties in optimizing the synthesis of new products.
The ‘Major Innovation’
The “major innovation” of the latest work lies in using multiple strains, rather than one, in the upcycling process, each of which plays different roles, the researchers said.
Compared to using monocultures, the latest approach demonstrated greater effectiveness at upcycling the plastic, which in the case of this study was polyethylene terephthalate, otherwise known as PET.
PET is one of the most common plastics in the world. It is often used to make containers for liquids and foods, such as bottles, as well as clothing fibers, among other applications.
In the latest study, the researchers developed two genetically engineered strains of the bacterium Pseudomonas putida for the purposes of degrading and upcycling PET.
“In this project, we built a duo of specialist bacteria, and deployed these strains to work collectively to fully convert plastics into valuable chemicals,” Lu and Collins said.
Two Main Steps
The biological conversion can be divided into two main steps: the breakdown of the plastic and the synthesis of new products.
First, the PET is broken down by the microbes into two compounds known as terephthalic acid (TPA) and ethylene glycol (EG). Then, the engineered microbes transform TPA and EGA into the products of interest. Each of the strains specializes in processing one of the two compounds.
The researchers found that using both strains together was more effective compared to using only a single strain that processed both products simultaneously.
“The plastic is completely degraded and converted through the process,” Lu said. “Early work based on single strains often result in incomplete utilization and inefficient product synthesis.”
Among the compounds that the bacteria produced was PHA, which is a biodegradable, eco-friendly alternative to petroleum-based plastics. The process also produced a substance known as muconate, which is a versatile “building block” chemical with numerous applications in agrochemicals, pharmaceuticals, and resins.
While the study primarily focused on the production of these two chemicals, the engineered microbes have the potential to be adapted in order to produce various other substances, the researchers said.
The Future of Plastic Waste
The latest findings suggest that engineering microbes may be a promising and effective approach to upcycling plastics. In addition, the underlying concept and strategies described in the paper are potentially applicable to the treatment of other types of plastic waste.
In practical terms, the researchers said they could envision two main real-world applications for their approach. The first is within industrial processing facilities, and the second is out in the natural environment.
“In the former case, plastic waste collected from oceans and landfills would be transported to a facility where it would be bioprocessed with engineered microbes. In our latter scenario, these microbes could be deployed directly in lands or oceans to bio-transform plastic debris in situ,” the researchers said.
While this approach is encouraging, several challenges remain that need to be addressed, particularly in the latter case. These challenges include the robustness and scalability of the engineered bacteria strains and the adaptability of the approach to different plastics, among others.
“Although these challenges lie ahead, I remain optimistic that bio-based upcycling holds the potential to play an important contribution to the mitigation of the plastic pollution problem,” Lu said.