and phone cases. This new bioplastic is filled with bacterial spores that, when exposed to nutrients found in compost, sprout and decompose the material once it reaches the end of its lifespan. The team’s findings were published in the journal Frontiers in Microbiology. The potential for this new bioplastic is significant, as it could potentially reduce the environmental impact of conventional plastics and contribute to a more sustainable future. The new bioplastic is not only biodegradable but also flexible and strong, making it suitable for a variety of commercial and industrial applications. Additionally, the use of bacterial spores in the breakdown process could offer a more natural and environmentally friendly alternative to traditional plastic disposal methods.cushions and memory foam. The biodegradable TPU is filled with bacterial spores that have the ability to break down plastic polymer materials when exposed to nutrients present in compost. This process allows the material to be broken down at the end of its life cycle.
The research was detailed in a paper published on April 30 in Nature Communications.
The TPU was created using bacterial spores from a strain of Bacillus subtilis that can break down plastic polymer materials.
“These bacteria have an inherent property to break down these materials,” explained Jon Pokorski, a nanoengineering professor at the UC San Diego Jacobs School of Engineering and co-lead author of the study.The Materials Research Science and Engineering Center (MRSEC) at the university conducted a study in which they assessed the ability of different strains to use TPUs as their main source of carbon. They then selected the strain that showed the best growth.
In their research, the scientists utilized bacterial spores, which are a dormant form of bacteria known for their ability to withstand harsh environmental conditions. Unlike fungal spores that are involved in reproduction, bacterial spores have a protective protein shield that allows bacteria to survive in a vegetative state.
To produce the biodegradable plastic, the researchers introduced Bacillus subtilis spores and TPU pellets into a plastic extruder. This process aimed to create a new material with enhanced properties.The ingredients were combined and heated to 135 degrees Celsius, then pushed out as thin plastic strips.
In order to test how easily the material breaks down, the strips were placed in both active compost and sterile compost environments. The compost setups were kept at 37 degrees Celsius with a relative humidity of 44 to 55%. The water and nutrients in the compost caused spores within the plastic strips to grow, and the strips were 90% degraded within five months.
“What’s impressive is that our material breaks down even without the presence of additional microbes,” said Pokorsk.i. “It is likely that the majority of these plastics will not be disposed of in composting facilities that are rich in microbes. Therefore, the ability of our technology to degrade in an environment without microbes makes it more flexible.”
While the researchers still need to examine the residue left behind after the material degrades, they emphasize that any remaining bacterial spores are probably not harmful. The strain Bacillus subtilis is used in probiotics and is generally considered safe for humans and animals — it can even be beneficial for plant health.
In this study, the bacterial spores were genetically modified to withstand the high temperatures required.The researchers utilized adaptive laboratory evolution to develop a strain that can withstand high extrusion temperatures for TPU production. This involved subjecting spores to increasing temperatures over time and allowing them to naturally mutate. The surviving strains were then isolated and put through the process again to further refine their heat tolerance. Adam Feist, a bioengineering research scientist at the UC San Diego Jacobs School of Engineering and co-senior author of the study, explained, “We continued to evolve the cells until we achieved a strain optimized to withstand the heat.”The process of bacterial evolution and selection has proven to be incredibly effective for this purpose,” said Pokorski. The spores also act as a strengthening filler, similar to how rebar reinforces concrete. This results in a TPU variant with superior mechanical properties, requiring more force to break and showing increased stretchability. “Simply by adding the spores, both of these properties are significantly enhanced,” Pokorski explained. “This is a major advancement because the addition of spores pushes the mechanical properties beyond previous limitations, where there was once a trade-off between tensile strength and stretchability.” The current study…The researchers are currently focused on scaling up production from lab-scale to industrial-scale to determine feasibility. They are working on optimizing their approach to produce larger quantities, evolving the bacteria to break down plastic materials faster, and exploring other types of plastics beyond TPU. According to Feist, there are various commercial plastics that end up in the environment, and TPU is just one of them. The next steps for the researchers involve broadening the scope of biodegradable materials that can be produced using this technology. This project received support from the U.S. Department of Energy.The research was funded by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy and Advanced Manufacturing Office (DE-EE0009296), UC San Diego Materials Research Science and Engineering Center (MRSEC), and the National Science Foundation (DMR-2011924).
Journal Reference:
- Han Sol Kim, Myung Hyun Noh, Evan M. White, Michael V. Kandefer, Austin F. Wright, Debika Datta, Hyun Gyu Lim, Ethan Smiggs, Jason J. Locklin, Md Arifur Rahman, Adam M. Feist, Jonathan K. Pokorski. Biocomposite thermoplastic polyurethanes containing evolved bacterial spores as living fillers to facilitate polymer disintegration.. The research was published in Nature Communications in 2024 and can be found in volume 15, issue 1. The DOI for this article is 10.1038/s41467-024-47132-8.
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