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Pollution Solution: Scientists Develop Living Plastics That Degrade in Compost or Erosion

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Saturday, August 31, 2024

Plastics are widely used but difficult to degrade, posing an ecological challenge. A team from SIAT developed degradable “living plastics” using synthetic biology and polymer engineering. They engineered Bacillus subtilis spores to produce Burkholderia cepacia lipase (BC-lipase), an enzyme that breaks down plastic. These spores were mixed with poly(caprolactone) (PCL) to create the plastics, maintaining the material’s physical properties. When the plastic surface is eroded, the spores release the enzyme, leading to a nearly complete breakdown of the plastic. Credit: Dai ZhuojunScientists developed engineered spores embedded in plastics that remain stable during use but degrade rapidly when exposed to specific environmental triggers. This innovative approach could significantly mitigate plastic pollution. The findings, led by Dr. Dai Zhuojun’s research group at the Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), were recently published in Nature Chemical Biology. The study leverages the natural resilience of spores, which can endure extreme environmental conditions, by programming them to secrete plastic-degrading enzymes under specific circumstances. These spores are embedded into plastic matrices through standard plastic processing methods, such as high temperature, high pressure, or the use of organic solvents. In normal conditions, the spores remain dormant, ensuring the plastic’s stable performance. However, when exposed to specific triggers like surface erosion or composting, the spores activate and initiate the degradation process, leading to the plastic’s complete breakdown. Research Background The invention of plastics has improved our daily lives, but the massive production and improper disposal of plastic waste have made plastic pollution a major environmental issue. In 2016, Yoshida et al. discovered a bacterium, Ideonella sakaiensis, in poly (ethylene terephthalate) (PET)-contaminated soil near a recycling facility in Japan. This bacterium can grow using PET as its main carbon source by producing two key enzymes: PETase and MHETase. Since then, numerous synthetic biology research has been focused on discovering, designing, and evolving the relevant plastic-degrading enzymes, but there has been little exploration of innovative methods for creating degradable plastics. Dormant Spores and Living Plastics Microorganisms have developed intrinsic mechanisms to defend against harsh conditions over billions of years. One classical example is the formation of spores that are resilient to dryness, high temperatures, and high pressure (similar conditions in plastics processing). Using synthetic biology, the research team engineered Bacillus subtilis with a genetic circuit to control the secretion of a plastic-degrading enzyme (lipase BC from Burkholderia cepacia). Under stress from heavy metal ions, Bacillus subtilis forms spores. The team mixed these engineered spores with poly (caprolactone) (PCL) plastic granules and produced spore-containing plastics through high-temperature extrusion or solvent dissolution. Tests showed that these “living plastics” had similar physical properties to regular PCL plastics. During daily use, the spores remain dormant, ensuring the plastic’s stable performance. Spore Release and Degradation Initiation The first key step in plastic degradation is to release the spores embedded in the living plastic for cell revival. Researchers have first demonstrated two methods of spore release. One method uses an enzyme (lipase CA) to erode the plastic surface. These released spores then germinated and expressed the lipase BC, which bound to the ends of PCL polymer chains and near-completely degraded the PCL molecules (final molecular weight <500 g/mol). The results showed that living plastic could degrade efficiently within 6-7 days, while ordinary PCL plastic subjected only to surface damage (lipase CA) still had a large amount of plastic debris after 21 days. Another method for spores release is composting. In the absence of any additional exogenous agents, living plastics in soil could completely degrade within 25-30 days, while traditional PCL plastic took about 55 days to degrade to a level that was invisible to the naked eye. Beyond PCL Plastics As mentioned earlier, PCL’s processing conditions are relatively ‘mild’ among plastics. To verify the system’s general applicability, the team continued to test other commercial plastic systems. They mixed spores carrying GFP expression plasmids with PBS (polybutylene succinate), PBAT (polybutylene adipate-co-terephthalate), PLA (polylactic acid), PHA (polyhydroxyalkanoates), and even PET (poly (ethylene terephthalate)) and processed the mixture at temperatures as high as 300oC. By releasing the spores through physical grinding, they surprisingly found that the spores could still revive and expressed the GFP. These results have laid a solid foundation for extending the method with other types of plastics. To validate the potential for scaling up the system, the research team also conducted a small-scale industrial test on PCL system using a single-screw extruder. The generated living PCL still exhibited rapid and efficient degradation property (degrade within 7 days). In the absence of external factors, the living PCL maintained a stable shape, demonstrating its robustness during the service (stable in Sprite for two months). This study provides a novel method for fabricating green plastics that can function steadily when the spores are latent and decay when the spores are aroused and shed light on the development of materials for sustainability. Reference: “Degradable living plastics programmed by engineered spores” by Chenwang Tang, Lin Wang, Jing Sun, Guangda Chen, Junfeng Shen, Liang Wang, Ying Han, Jiren Luo, Zhiying Li, Pei Zhang, Simin Zeng, Dianpeng Qi, Jin Geng, Ji Liu and Zhuojun Dai, 21 August 2024, Nature Chemical Biology.DOI: 10.1038/s41589-024-01713-2

Scientists developed engineered spores embedded in plastics that remain stable during use but degrade rapidly when exposed to specific environmental triggers. This innovative approach could significantly mitigate plastic pollution. The findings, led by Dr. Dai Zhuojun’s research group at the Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), were recently published in [...]

Living Plastics Degradation
Plastics are widely used but difficult to degrade, posing an ecological challenge. A team from SIAT developed degradable “living plastics” using synthetic biology and polymer engineering. They engineered Bacillus subtilis spores to produce Burkholderia cepacia lipase (BC-lipase), an enzyme that breaks down plastic. These spores were mixed with poly(caprolactone) (PCL) to create the plastics, maintaining the material’s physical properties. When the plastic surface is eroded, the spores release the enzyme, leading to a nearly complete breakdown of the plastic. Credit: Dai Zhuojun

Scientists developed engineered spores embedded in plastics that remain stable during use but degrade rapidly when exposed to specific environmental triggers. This innovative approach could significantly mitigate plastic pollution.

The findings, led by Dr. Dai Zhuojun’s research group at the Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), were recently published in Nature Chemical Biology.

The study leverages the natural resilience of spores, which can endure extreme environmental conditions, by programming them to secrete plastic-degrading enzymes under specific circumstances. These spores are embedded into plastic matrices through standard plastic processing methods, such as high temperature, high pressure, or the use of organic solvents.

In normal conditions, the spores remain dormant, ensuring the plastic’s stable performance. However, when exposed to specific triggers like surface erosion or composting, the spores activate and initiate the degradation process, leading to the plastic’s complete breakdown.

Research Background

The invention of plastics has improved our daily lives, but the massive production and improper disposal of plastic waste have made plastic pollution a major environmental issue. In 2016, Yoshida et al. discovered a bacterium, Ideonella sakaiensis, in poly (ethylene terephthalate) (PET)-contaminated soil near a recycling facility in Japan.

This bacterium can grow using PET as its main carbon source by producing two key enzymes: PETase and MHETase. Since then, numerous synthetic biology research has been focused on discovering, designing, and evolving the relevant plastic-degrading enzymes, but there has been little exploration of innovative methods for creating degradable plastics.

Dormant Spores and Living Plastics

Microorganisms have developed intrinsic mechanisms to defend against harsh conditions over billions of years. One classical example is the formation of spores that are resilient to dryness, high temperatures, and high pressure (similar conditions in plastics processing).

Using synthetic biology, the research team engineered Bacillus subtilis with a genetic circuit to control the secretion of a plastic-degrading enzyme (lipase BC from Burkholderia cepacia). Under stress from heavy metal ions, Bacillus subtilis forms spores. The team mixed these engineered spores with poly (caprolactone) (PCL) plastic granules and produced spore-containing plastics through high-temperature extrusion or solvent dissolution. Tests showed that these “living plastics” had similar physical properties to regular PCL plastics. During daily use, the spores remain dormant, ensuring the plastic’s stable performance.

Spore Release and Degradation Initiation

The first key step in plastic degradation is to release the spores embedded in the living plastic for cell revival. Researchers have first demonstrated two methods of spore release. One method uses an enzyme (lipase CA) to erode the plastic surface.

These released spores then germinated and expressed the lipase BC, which bound to the ends of PCL polymer chains and near-completely degraded the PCL molecules (final molecular weight <500 g/mol). The results showed that living plastic could degrade efficiently within 6-7 days, while ordinary PCL plastic subjected only to surface damage (lipase CA) still had a large amount of plastic debris after 21 days.

Another method for spores release is composting. In the absence of any additional exogenous agents, living plastics in soil could completely degrade within 25-30 days, while traditional PCL plastic took about 55 days to degrade to a level that was invisible to the naked eye.

Beyond PCL Plastics

As mentioned earlier, PCL’s processing conditions are relatively ‘mild’ among plastics. To verify the system’s general applicability, the team continued to test other commercial plastic systems. They mixed spores carrying GFP expression plasmids with PBS (polybutylene succinate), PBAT (polybutylene adipate-co-terephthalate), PLA (polylactic acid), PHA (polyhydroxyalkanoates), and even PET (poly (ethylene terephthalate)) and processed the mixture at temperatures as high as 300oC.

By releasing the spores through physical grinding, they surprisingly found that the spores could still revive and expressed the GFP. These results have laid a solid foundation for extending the method with other types of plastics.

To validate the potential for scaling up the system, the research team also conducted a small-scale industrial test on PCL system using a single-screw extruder. The generated living PCL still exhibited rapid and efficient degradation property (degrade within 7 days). In the absence of external factors, the living PCL maintained a stable shape, demonstrating its robustness during the service (stable in Sprite for two months). This study provides a novel method for fabricating green plastics that can function steadily when the spores are latent and decay when the spores are aroused and shed light on the development of materials for sustainability.

Reference: “Degradable living plastics programmed by engineered spores” by Chenwang Tang, Lin Wang, Jing Sun, Guangda Chen, Junfeng Shen, Liang Wang, Ying Han, Jiren Luo, Zhiying Li, Pei Zhang, Simin Zeng, Dianpeng Qi, Jin Geng, Ji Liu and Zhuojun Dai, 21 August 2024, Nature Chemical Biology.
DOI: 10.1038/s41589-024-01713-2

Read the full story here.
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Environmental Agency Denies Petition to Designate Big Hole River as Impaired by Nutrient Pollution

Montana’s environmental regulator has denied a petition to designate the Big Hole River as impaired by nitrogen and phosphorus

Montana’s environmental regulator has denied a petition to designate the Big Hole River as impaired by nitrogen and phosphorus, throwing a wrench in environmentalists’ efforts to put the blue-ribbon fishery on a “pollution diet.”Upper Missouri Waterkeeper and the Big Hole River Foundation contend that excess nutrients are creating regular summertime algal blooms that can stretch for more than a mile, robbing fish and the macroinvertebrate bugs they eat of the oxygen they need to thrive. The groups argue in the petition they sent to the Montana Department of Environmental Quality last month that an impairment designation would direct the agency to identify and work to reduce the river’s pollution sources in an effort to rebalance the river’s aquatic ecosystem.On April 14, about a month after receiving the 32-page petition, DEQ wrote that it “cannot grant” the group’s petition. The agency’s letter doesn’t quibble with the groups’ findings, which were detailed in a five-year data collection effort. Instead, the agency suggested that legislation passed in 2021 has tied its hands. “As a result of Senate Bill 358, passed during the 2021 Legislative Session … DEQ is unable to base nutrient assessment upon the numeric nutrient criteria,” the letter, signed by DEQ Director Sonja Nowakowski, reads. In an April 23 conversation with Montana Free Press, Upper Missouri Waterkeeper Executive Director Guy Alsentzer criticized the agency’s decision, arguing that it did not use the best available science and applied “illogical and disingenuous” reasoning in its denial. “EPA already took action and struck down Senate Bill 358 from the 2021 session,” Alsentzer said, referencing federal regulators’ oversight of state laws and rules governing water quality. “Numeric criteria are applicable.”A spokesperson for the EPA confirmed Alsentzer’s assertion, writing in an April 24 email to MTFP that numeric nutrient standards for nitrogen and phosphorus the agency approved a decade ago “remain in effect for Clean Water Act purposes” and will remain so “unless or until the EPA approves the removal of the currently applicable numeric nutrient criteria and approves revised water quality standards.”A DEQ spokesperson did not directly answer MTFP’s questions about what water quality standards DEQ is using to assess Montana waterways and determine whether permittees are complying with state and federal regulations.The agency wrote in an email that no permitted pollution sources under its regulatory oversight are discharging into the Big Hole, suggesting that its enforcement role is limited. The agency also wrote that an impairment designation is not required to implement water quality improvement projects such as creating riparian buffers, improving forest roads, or creating shaded areas. “Watershed partners may begin actively working on nonpoint source pollution reduction projects at any time,” DEQ spokesperson Madison McGeffers wrote to MTFP. “There is nothing standing in the way of starting work on these types of projects to improve water quality. In fact, the Big Hole River Watershed Committee is actively implementing its Watershed Restoration Plan with funds and support from DEQ Nonpoint Source & Wetland Section’s 319 program.”Alsentzer countered that a science-based cleanup plan and greater accountability will benefit the Big Hole regardless of whether nutrients are flowing into the river from a pipe or entering via more diffuse and harder-to-regulate channels.“You can’t get to that if you don’t recognize that you’ve got a problem we need to solve,” he said, adding that an impairment designation “unlocks pass-through funding to the tune of millions of dollars.”Addressing manmade threats to the Big Hole should be a priority for DEQ, given local communities’ economic reliance on a healthy river, he added.“It’s just a real tragic state of affairs when you have a blue-ribbon trout fishery in a very rural county that’s essentially having its livelihood flushed down the drain because we can’t get our agencies to actually implement baseline river protections (and) use science-based standards,” Alsentzer said. “When people try to do the work for the agency and help them, they’re getting told to go pound sand. I think that’s wrong.”Two years ago, Montana Fish, Wildlife and Parks biologists recorded historically low numbers of brown trout along some stretches of the Big Hole. Anglers and conservationists floated a number of possible contributing factors, ranging from pathogens and drought conditions to angling pressure and unmitigated pollution. Save Wild Trout, a nonprofit formed in 2023 to understand which factors merit further investigation, described the 2023 southwestern Montana fishery “collapse” as a “canary in the coal mine moment.”In response to the 2023 population slump, Gov. Greg Gianforte announced the launch of a multiyear research effort on Jefferson Basin rivers that FWP is coordinating with Montana State University. Narrative Standards For ‘Undesirable Aquatic Life’ DEQ’s letter to Upper Missouri Waterkeeper and the Big Hole River Foundation leaves open the possibility of a future impairment designation based on narrative water quality standards. After mentioning the 2021 legislation, Nowakowski wrote that the agency reviewed the submitted data “along with other readily available data, in consideration of the state’s established narrative criteria.”The letter goes on to outline the additional material petitioners would need to submit for the agency to evaluate an impairment designation using narrative criteria, which establish that surface waters must be “free from substances” that “create conditions which produce undesirable aquatic life.”In an April 22 letter, Upper Missouri Waterkeeper and the Big Hole River Foundation addressed the petition denial in two parts. First, the groups argued that numeric nutrient standards apply. Second, they resubmitted material — photos, emails, a macroinvertebrate report, and “Aquatic Plant Visual Assessment Forms” — to support an impairment designation under the looser narrative standards. “We encourage DEQ to do the right thing, use all available science to determine the Big Hole River impaired for nutrients, and commit to working with petitioners and other (stakeholders) in addressing the pollution sources undermining this world-class waterway and harming the diverse uses it supports,” the letter says. Alsentzer noted that he has set up a meeting with the EPA to discuss DEQ’s treatment of the petition and its description of applicable water quality standards.The dispute over numeric nutrient standards comes shortly after the Legislature passed another bill seeking to repeal them. Any day now, Gianforte is expected to sign House Bill 664, which bears a striking similarity to 2021’s Senate Bill 358. HB 664 has garnered support from Nowakowski, who described it as a “time travel” bill that will return the state to “individual, site-by-site” regulations in lieu of more broadly applicable numeric standards. This story was originally published by Montana Free Press and distributed through a partnership with The Associated Press.Copyright 2025 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.Photos You Should See - Feb. 2025

Supreme Court justices consider reviving industry bid to ax California clean car rule

The Supreme Court on Wednesday heard oral arguments in a case that could revive a bid by fuel producers to ax California’s clean car standards. The court was not considering the legality of the standards themselves, which ​​require car companies to sell new vehicles in the state that produce less pollution — including by mandating...

The Supreme Court on Wednesday heard oral arguments in a case that could revive a bid by fuel producers to ax California’s clean car standards. The court was not considering the legality of the standards themselves, which ​​require car companies to sell new vehicles in the state that produce less pollution — including by mandating a significant share of cars sold to be electric or hybrid.  Instead, the Supreme Court was considering whether the fuel industry had the authority to bring the lawsuit at all. A lower court determined that the producers, which include numerous biofuel companies and trade groups representing both them and the makers of gasoline, did not have standing to bring the case. Some of the justices were quiet, so it’s difficult to predict what the ultimate outcome of the case will be. However, others appeared critical of the federal government and California’s arguments that the fuel producers do not have the right to bring a suit. Justice Brett Kavanaugh in particular noted that the Environmental Protection Agency (EPA) itself did not initially try to have the case tossed on that basis.  “Isn't that a tell here? I mean, EPA, as you, of course, know, routinely raises standing objections when there's even — even a hint of a question about it,” Kavanaugh said.  The fuel producers argued that while it was technically the auto industry that was being regulated, the market was being “tilted” against them as well by California’s rule, which was also adopted by other states. The EPA and California have argued that the fuel producers are arguing on the basis of outdated facts and a market that has shifted since the rule was first approved by the EPA in 2013.  The EPA needs to grant approval to California to issue such rules. The approval was revoked by the Trump administration and later reinstated in the Biden administration.  If the justices revive the currently dismissed case, lower courts would then have to decide whether to uphold the California rule — though the underlying case could eventually make its way to the high court as well.  Meanwhile, California has since passed subsequent standards that go even further — banning the sale of gas-powered cars in the state by 2035. That rule was approved by the Biden administration — though Congress may try to repeal it.

EPA fires or reassigns hundreds of staffers

The Environmental Protection Agency plans to fire or reassign more than 450 staffers working on environmental justice issues, it said Tuesday.Why it matters: The large-scale changes could effectively end much of the EPA's work tackling pollution in historically disadvantaged communities.It's part of the Trump administration's effort to vastly shrink the federal workforce. EPA has around 15,000 employees.Driving the news: EPA notified roughly 280 employees that they will be fired in a "reduction in force." Another 175 who perform "statutory functions" will be reassigned.The employees come from the Office of Environmental Justice and External Civil Rights, the Office of Inclusive Excellence, and EPA regional offices."EPA is taking the next step to terminate the Biden-Harris Administration's Diversity, Equity, and Inclusion and Environmental Justice arms of the agency," a spokesperson said.Between the lines: The firings will likely see challenges from congressional Democrats and the employees themselves.EPA had previously put many environmental justice staffers on administrative leave.Administrator Lee Zeldin, during a Monday news conference, defended the agency's broader efforts to cut environmental justice grant programs, arguing the money is ill-spent."The problem is that, in the name of environmental justice, a dollar will get secured and not get spent on remediating that environmental issue," he said.

The Environmental Protection Agency plans to fire or reassign more than 450 staffers working on environmental justice issues, it said Tuesday.Why it matters: The large-scale changes could effectively end much of the EPA's work tackling pollution in historically disadvantaged communities.It's part of the Trump administration's effort to vastly shrink the federal workforce. EPA has around 15,000 employees.Driving the news: EPA notified roughly 280 employees that they will be fired in a "reduction in force." Another 175 who perform "statutory functions" will be reassigned.The employees come from the Office of Environmental Justice and External Civil Rights, the Office of Inclusive Excellence, and EPA regional offices."EPA is taking the next step to terminate the Biden-Harris Administration's Diversity, Equity, and Inclusion and Environmental Justice arms of the agency," a spokesperson said.Between the lines: The firings will likely see challenges from congressional Democrats and the employees themselves.EPA had previously put many environmental justice staffers on administrative leave.Administrator Lee Zeldin, during a Monday news conference, defended the agency's broader efforts to cut environmental justice grant programs, arguing the money is ill-spent."The problem is that, in the name of environmental justice, a dollar will get secured and not get spent on remediating that environmental issue," he said.

EPA firing 280 staffers who fought pollution in overburdened neighborhoods

The Environmental Protection Agency (EPA) will fire 280 staffers who worked on tackling pollution in overburdened and underserved communities and will reassign another 175. These staffers worked in an area known as “environmental justice,” which helps communities that face a disproportionate amount of pollution exposure, especially minority or low-income communities.  The EPA has framed its...

The Environmental Protection Agency (EPA) will fire 280 staffers who worked on tackling pollution in overburdened and underserved communities and will reassign another 175. These staffers worked in an area known as “environmental justice,” which helps communities that face a disproportionate amount of pollution exposure, especially minority or low-income communities.  The EPA has framed its efforts to cut these programs — including its previous closure of environmental justice offices — as part of a push to end diversity programming in the government. Supporters of the agency's environmental justice work have pointed out that Black communities face particularly high pollution levels and that the programs also help white Americans, especially if they are poor.  “EPA is taking the next step to terminate the Biden-Harris Administration’s Diversity, Equity, and Inclusion and Environmental Justice arms of the agency,” an EPA spokesperson said in a written statement.   “Today, EPA notified diversity, equity, and inclusion and environmental justice employees that EPA will be conducting a Reduction in Force,” the spokesperson said. “The agency also notified certain statutory and mission essential employees that they are being reassigned to other offices through the ‘transfer of function’ procedure also outlined in [the Office of Personnel Management’s] Handbook and federal regulations” The firings will be effective July 31, according to E&E News, which first reported that they were occurring. The news comes as the Trump administration has broadly sought to cut the federal workforce. The administration has previously indicated that it planned to cut 65 percent of the EPA’s overall budget. It’s not clear how much of this will be staff, though according to a plan reviewed by Democrat House staff, the EPA is considering the termination of as many as about 1,100 employees from its scientific research arm.  Meanwhile, as part of their reductions in force, other agencies including the Department of Health and Human Services and the Department of Veterans Affairs have fired tens of thousands of staffers. The EPA is smaller than these agencies, with a total of more than 15,000 employees as of January.  Nearly 170 environmental justice staffers were previously placed on paid leave while the agency was “in the process of evaluating new structure and organization.”

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