Thursday, July 24, 2025

AUSTERITY HANGOVER

Annual UK cost of mental health disorder PTSD likely tops £40 billion

But figures based on 2020-21 data and don’t include all indirect costs; Societal and financial impacts of increasingly common condition “gravely” undervalued

BMJ Group

The annual UK cost of the mental health disorder PTSD is likely to top £40 billion, but the figures are based on 2020-1 prevalence rates—the most recently available—and don’t include many indirect costs, such as family support services, finds a cost analysis published in the open access journal BMJ Open.

The societal and financial impacts of this increasingly common condition have been “gravely” undervalued, conclude the researchers.

Post-traumatic stress disorder, more commonly referred to as PTSD, usually develops after witnessing or experiencing a traumatic event or being subjected to a more systematic pattern of trauma or abuse, explain the researchers.

Those experiencing physical violence, life-threatening injury, sexual abuse, active military combat, first responders and aid workers in humanitarian disasters may all be at risk.

Yet, despite an anticipated rise in cases of 77,000 a year, primarily due to the COVID-19 pandemic, PTSD continues to be misunderstood, stigmatised, and often misdiagnosed, say the researchers. Evaluating its economic toll is therefore crucial to inform policymakers about the importance of PTSD and the provision of care, they add.

They calculated an overall lifetime prevalence of around 4% for 2020-21—equivalent to 6,665,000 people who are expected to develop PTSD at some point in their life—from available military and civilian data.

And they searched databases for all types of quantitative studies evaluating the economic and societal costs associated with PTSD, published in English between 1990 and 2023.

Five studies involving millions of people were eligible for the analysis. From these they extracted and pooled direct cost components: hospital stays; drug treatment; family doctor (GP) and specialist (psychiatrist) time; treatment for alcohol and/or substance misuse; costs of counsellors and psychologists.

Similarly, they extracted and pooled indirect cost components: homelessness; disability living allowance; unemployment allowance; lost productivity at work (absenteeism and presenteeism); domiciliary care; social worker costs (mental health); and premature death.

At 2020-1 prices, they estimated the annual average direct excess costs for a patient with PTSD in the UK to be around £1,118, and the annual average indirect costs to be around £13,663, adding up to a total of £14,781, but ranging from around £11,373 to £16,797.

Based on the prevalence figures for 2020-1, this comes to more than £40 billion a year, they calculate.

The researchers acknowledge that PTSD is often present with other mental health conditions, and disentangling the costs due to PTSD alone is difficult. The severity of the condition (and therefore associated treatment costs) also varies.

“Certain costs are hard to measure, such as stigma and discrimination, for which we have provided only a qualitative analysis. These in turn may lead to indirect costs, such as reduced income and higher dependence on social security assistance,” they write.

But they say: “Recognising the hidden costs of PTSD (eg, in criminal justice, family support services and education) for which we were unable to provide estimates, suggests the actual economic burden is higher than estimated here,” adding: “we are gravely underquantifying the cost of this increasingly prevalent condition.”

They suggest: “The UK would do well to consider the need for the collection of high-quality cost data to more accurately assess the different costs associated with this condition. These include the involvement of individuals affected by PTSD in criminal activities, the stigma and discrimination they face, leading to social exclusion, the impact on personal relationships, and the effect on education, potentially limiting future opportunities.”

And they conclude that their findings underscore: “the need for increased awareness of PTSD, the development of more effective therapies, and the expansion of evidence-based interventions to alleviate the substantial disease and economic burden of PTSD in the UK.”

Journal

BMJ Open

DOI

10.1136/bmjopen-2024-084394

Method of Research

Systematic review

Subject of Research

People

Article Title

Economic burden of PTSD in the UK: a systematic review and economic analysis

Article Publication Date

22-Jul-2025

Early warning system could prevent a stink when it comes to street tree roots blocking sewer pipes

Tree roots the most common cause of pipe failures worldwide

SCIENCE FOR EVERYDAY LIFE

University of South Australia

Researchers at the University of South Australia are calling for a major shift in how cities manage tree root intrusions into household sewer systems that cost millions of dollars in repair bills each year.

A new study by UniSA’s Sustainable Infrastructure and Resource Management (SIRM) team reveals that current maintenance strategies are falling short, resulting in repeated pipe blockages, environmental contamination, and mounting damage bills.

Instead, the engineering researchers propose a smarter, preventative approach using predictive analytics to identify high-risk areas before damage occurs.

In a new paper published in Sustainability, the UniSA team reviewed global literature and maintenance practices, concluding that removing tree roots using mechanical and chemical measures is not the best solution. Roots can grow back, and the damage is costly to fix.

In Adelaide alone, SA Water reported more than 30,000 cases of tree root intrusion in 2020, accounting for nearly 60% of all sewer failures. Each year, the utility spends approximately $5 million on repair works and maintenance caused by blocked sewer pipes.

Tree root intrusions are a global headache, costing countries millions of dollars each year. Worldwide, remediation options include mechanical and chemical techniques to clear pipe systems and control root growth, as well as proactive approaches such as planting trees well clear of pipes.

But the traditional responses are only temporary fixes, according to UniSA Water Science and Engineering Professor Chris Chow, a senior author on the paper.

“Tree roots are the most common cause of pipe failures in many cities around the world,” Prof Chow says.

“The challenge is that cutting roots or applying chemicals are not permanent solutions. The chemicals can contaminate the soil, and the roots often grow back more aggressively.”

Instead, his team is advocating for a predictive approach, analysing key risk factors – such as pipe age, material, diameter, soil type, tree species and climate conditions – so that water utilities can model where tree root problems are most likely to occur.

“It’s essentially an early warning system,” says lead author Oliver Yang, a Master of Research graduate at UniSA.

“We can map out high-risk zones and guide smarter planting choices, better pipe materials and targeted maintenance,” Yang says.

While predictive models already exist for pipe failures based on material or age, few incorporate environmental or vegetation factors. This gap is significant, the researchers say, given the complex interactions between roots, soil, moisture and infrastructure.

Fast growing species such as eucalyptus, poplars, willows, jacarandas and desert ash are particularly aggressive, with root systems that can spread many metres in search of water – especially in dry or compacted soils.

Trees such as hackberry, varnish or lacquer species, brush box, willow myrtle and kurrajong trees are less intrusive and better choices for street planting.

“Globally, cities are spending millions each year fixing the same problems over and over,” says Yang. “With the right data and modelling, we can address this, saving money, protecting infrastructure and still enjoying the benefits of urban greenery.”

The researchers are calling for more region-specific studies and the development of locally-calibrated predictive tools that incorporate tree, pipe, soil and environmental factors.

‘Review of Root Intrusions by Street Trees and Utilising Predictive Analytics to Improve Water Utility Maintenance Strategies’ is published in Sustainability. DOI: 10.3390/su17125263

Journal

Sustainability

DOI

10.3390/su17125263

Method of Research

Computational simulation/modeling

Article Title

Review of Root Intrusions by Street Trees and Utilising Predictive Analytics to Improve Water Utility Maintenance Strategies

Interference to astronomy the unintended consequence of faster internet

Curtin University

Curtin University researchers have undertaken the world’s biggest survey of low frequency satellite radio emissions, finding Starlink satellites are significantly interfering with radio astronomy observations, potentially impacting discovery and research.

Unintended signals from satellites - leaked from onboard electronics - can drown out the faint radio waves astronomers use to study the universe.

Researchers from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), hosted at the Curtin Institute of Radio Astronomy (CIRA), focused on the Starlink mega-constellation as it has the most satellites in orbit, at more than 7000 during the time of the study.

Starlink is a private satellite internet service launched by aerospace company, SpaceX, which promises faster internet connections, particularly for rural and remote areas.

The research team collected and analysed 76 million images of the sky using a prototype station for the Square Kilometre Array (SKA), which will be the world’s largest and most sensitive radio telescope once fully built later this decade.

PhD candidate and study lead Dylan Grigg said the team detected more than 112,000 radio emissions from 1806 Starlink satellites, making it the most comprehensive catalogue of satellite radio emissions at low frequencies to date.

“Starlink is the most immediate and frequent source of potential interference for radio astronomy: it launched 477 satellites during this study’s four-month data collection period alone,” Mr Grigg said.

“In some datasets, we found up to 30 per cent of our images showed interference from a Starlink satellite.”

Mr Grigg said the issue wasn’t just the number of satellites, but the strength of the signals and the frequencies they were visible at.

“Some satellites were detected emitting in bands where no signals are supposed to be present at all, such as the 703 satellites we identified at 150.8 MHz, which is meant to be protected for radio astronomy,” Mr Grigg said.

“Because they may come from components like onboard electronics and they’re not part of an intentional signal, astronomers can’t easily predict them or filter them out.”

CIRA Executive Director and study co-author John Curtin Distinguished Professor Steven Tingay said there was scope for regulatory improvement to help avoid satellites interfering with research.

“Current International Telecommunication Union regulations focus on intentional transmissions and do not cover this type of unintended emission,” Professor Tingay said.

“Starlink isn’t the only satellite network, but it is by far the biggest and its emissions are now increasingly prominent in our data.

“We hope this study adds support for international efforts to update policies that regulate the impact of this technology on radio astronomy research, that are currently underway.

“It is important to note that Starlink is not violating current regulations, so is doing nothing wrong. Discussions we have had with SpaceX on the topic have been constructive.”

Professor Tingay said satellite technology and radio astronomy were both important but needed to exist in harmony.

“We’re standing on the edge of a golden era where the SKA will help answer the biggest questions in science: how the first stars formed, what dark matter is and even test Einstein’s theories,” Professor Tingay said.

“But it needs radio silence to succeed. We recognise the deep benefits of global connectivity but we need balance and that starts with an understanding of the problem, which is the goal of our work.”

‘The Growing Impact of Unintended Starlink Broadband Emission on Radio Astronomy in the SKA-Low Frequency Range’ was published in Astronomy and Astrophysics.

Journal

Astronomy and Astrophysics

DOI

10.1051/0004-6361/202554787

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

The growing impact of unintended Starlink broadband emission on radio astronomy in the SKA-Low frequency range

Article Publication Date

17-Jul-2025

Students more likely to pass oral exams at noon — and that might apply to job interviews, too

Physiological rhythms could explain why Italian university students were more likely to fail exams early or late in the day

Frontiers

To succeed at university, Italian students need to pass interview-style oral exams. Now scientists have found that the time of the exam could be a critical factor influencing their success… or failure. Even when other factors were excluded, the chances of passing were highest around lunchtime, and lowest at the beginning or end of the day.

“We show that academic assessment outcomes vary systematically across the day, with a clear peak in passing rates around midday,” said Prof Carmelo Mario Vicario, director of the Social-Cognitive Neuroscience Lab at the University of Messina and lead author of the article in Frontiers in Psychology. “Students were more likely to pass in late morning compared to early morning or late afternoon.”

“We believe this pattern could extend to job interviews or any evaluative process scheduled throughout the day,” added Vicario. “We would be very interested in investigating whether hiring decisions, too, fluctuate in fairness or outcome depending on time of day.”

Timing is everything

The researchers were inspired by work which showed that judges were most likely to rule in favor of a defendant after meal breaks or at the beginning of a session. However, this could have been influenced by different types of case being presented at different times. So the researchers looked at oral exams, which are more subjective than legal decisions. If the time of day influences people’s judgement, large-scale data on exam outcomes should show evidence of it.

“Oral exams in Italian universities are scheduled at set times, typically lasting 10 to 30 minutes per student,” explained Vicario. “There's no standardized format: professors ask questions based on the course content, and grades are assigned on the spot. These exams can be highly stressful due to their unpredictable nature and the strong weight they carry in academic progression.”

A database from the University of Messina allowed researchers to access the results of exams conducted between October 2018 and February 2020. The researchers collected the time, date, and outcome of 104,552 assessments delivered by 680 examiners for 1,243 courses. They also used the number of credits granted towards a degree per exam to measure the difficulty of individual exams. This allowed them to exclude the difficulty of the exam as a factor and carry out statistical analysis evaluating the likelihood of passing based on the time when the exam began.

Beating the curve

The researchers found that only 57% of the exams were passed. The passing rate followed a bell curve with a peak at noon: there was no significant difference in your chance of passing if you sat your exam at 11:00 or 13:00, but your chances of passing were lower if you took the exam at 08:00 or 09:00, or at 15:00 or 16:00. The chance of passing was equivalent in the early morning and in the late afternoon.

"These findings have wide-ranging implications,” commented Prof Alessio Avenanti of the University of Bologna, co-author of the study. “They highlight how biological rhythms — often overlooked in decision-making contexts — can subtly but significantly shape the outcome of high-stakes evaluations."

Although the study can’t identify the mechanisms behind this pattern, the peak in passes at midday is consistent with evidence that cognitive performance improves over the course of the morning before declining during the afternoon. Students’ falling energy levels could lead to diminishing focus, compromising their performance. Professors might also be experiencing decision fatigue, leading them to mark more harshly.

Meanwhile, poorer results earlier in the day could be down to competing chronotypes. People in their early 20s are usually night owls, while people in their 40s or older tend to be morning larks. The students might be least cognitively sharp at the time when the professors are most alert.

“To counteract time-of-day effects, students might benefit from strategies like ensuring quality sleep, avoiding scheduling important exams during personal ‘low’ periods, and taking mental breaks before performance tasks,” suggested Vicario. “For institutions, delaying morning sessions or clustering key assessments in the late morning may improve outcomes.”

But more research is needed to fully understand the factors which contribute to the time of day’s influence on students’ performance, and develop ways of improving the fairness of assessments.

“While we controlled for exam difficulty, we can’t entirely exclude other unmeasured factors,” said Prof Massimo Mucciardi of the University of Messina, senior author. “We couldn’t access detailed student- or examiner-level data such as sleep habits, stress, or chronotype. This is why we encourage follow-up studies using physiological or behavioral measures to uncover the underlying mechanisms.”

Journal

Frontiers in Psychology

DOI

10.3389/fpsyg.2025.1605041

Method of Research

Observational study

Subject of Research

People

Article Title

Timing matters! Academic assessment changes throughout the day

Article Publication Date

24-Jul-2025

COI Statement

The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision

New research details how our brains are drawn to and spot faces everywhere

University of Surrey

New research details how our brains are drawn to and spot faces everywhere

If you have ever spotted faces or human-like expressions in everyday objects, you may have experienced the phenomenon of face pareidolia. Now, a new study by the University of Surrey has looked into how this phenomenon grabs our attention, which could be used by advertisers in promoting future products.

The study, published in i-Perception, investigated the differences between our attention being directed by averted gazes – when a subject looks away from another subject’s eyes or face – and when it’s directed by pareidolia – imagined face-like objects.

The researchers conducted four “gaze cueing task” experiments with a total of 54 participants, to measure how our attention is influenced by the direction of another subject’s gaze. They found that participants consistently shifted their attention in response to the appearance of both averted gazes and pareidolia.

However, the underlying mechanisms through which attention is drawn are quite different. While we are primarily drawn to the eye region of averted gazes, we are drawn to pareidolia’s holistic structure of their “faces”, and as a result, experienced a stronger response and attention.

Dr Di Fu, Lecturer in Cognitive Neuroscience at the University of Surrey, said:

"Our research shows that both averted gazes from real faces and perceived faces in objects can direct where we look, but they do so through different pathways. We process real faces through focusing on specific features, like the direction of the eyes. However, with face-like objects, we process their overall structure and where their “eye-like features” are positioned, resulting in a stronger attention response.”

The findings of the study may have implications that go beyond a better understanding of how our brain processes information. Dr Fu adds:

"Our findings may have practical implications too, particularly in areas like product advertising. Advertisers could potentially incorporate face-like arrangements with prominent eye-like elements into their designs, increasing consumer attention and leaving a more memorable impression of their products."

[ENDS]

Dr Di Fu is available for interview, please contact mediarelations@surrey.ac.uk to arrange.

The full paper is available upon request, DOI: 10.1177/20416695251352129

An image of Dr Fu is available upon request.

Journal

i-Perception

DOI

10.1177/20416695251352129

US National study finds healthcare provider stigma toward substance use disorder varies sharply by condition and provider

Emergency medicine physicians show highest stigma—but also play crucial role in linking patients to treatment

Columbia University's Mailman School of Public Health

A new national study from Columbia University Mailman School of Public Health, with colleagues at the University of Miami Miller School of Medicine, University of Chicago, National Opinion Research Center, and Emory University finds that stigma toward patients with substance use disorders (SUD) remains widespread among U.S. healthcare providers—and varies significantly across types of substances. The findings are published in the journal Addiction.

The study is the first national analysis to compare provider stigma across opioid (OUD), stimulant, and alcohol use disorders (AUD) with other chronic but often-stigmatized conditions like depression, HIV, and Type II diabetes. Researchers also assessed how stigma influences whether providers screen for SUD, offer referrals, or deliver treatment.

“While we've made progress in expanding access to evidence-based SUD treatment, stigma remains a profound barrier—often embedded in the clinical encounter itself,” said Carrigan Parish, DMD, PhD, assistant professor in the Department of Sociomedical Sciences at Columbia Mailman School of Public Health. “Our findings show that many providers still feel uncomfortable treating patients with substance use disorders and that hesitancy leads directly to missed opportunities for care. In particular, emergency departments often serve as the first—and sometimes only—point of care for people with substance use disorders. We need to leverage those moments, not miss them.”

The study, conducted from October 2020 to October 2022, surveyed 1,081 primary care providers (PCPs), 600 emergency medicine providers (EMPs), and 627 dentists using a nationally representative random sample licensed from the American Medical and Dental Associations. Participants rated their agreement with 11 standardized stigma statements and reported their screening, referral, and treatment practices for six conditions: three SUDs (opioids, stimulants, alcohol) and three comparison medical conditions (Type II diabetes, depression, HIV).

Key findings:

Stigma score toward stimulant use disorders was highest (36.3 points, followed by OUD (35.6 points) and AUD (32 points).
For comparison, stigma scores were far lower for depression (26.2 points, HIV (25.8 points), and Type II diabetes (23.2 points), where providers also reported higher levels of compassion and treatment.
More than 30 percent of providers said they prefer not to work with patients with OUD or stimulant use disorders—compared to just 2 percent for diabetes, and 9 percent for both HIV and depression.
Emergency medicine physicians (EMPs) expressed the highest levels of stigma toward SUD, yet were also the most active in providing clinical care:
- 28.4 percent reported providing drug use treatment
- 27.2 percent prescribed medications for opioid use disorder (MOUD) compared to just 12 percent and 10 percent of primary care physicians (PCPs) for drug use treatment and prescribing medications, respectively.
Dentists reported the lowest stigma levels toward all queried conditions—which may be due to greater clinical and moral distance from SUD treatment and viewing SUD-related practices as outside their scope of practice
Stigma scores did not significantly differ by provider race, age, gender, region, or rurality, indicating that these attitudes span the healthcare workforce

“Overall, providers were less likely to feel they could effectively help patients with stimulant or opioid use disorders. In fact, 22 percent of providers said, ‘there is little I can do to help patients like this’—a response we almost never saw for other conditions,” said Daniel Feaster, PhD and professor of Biostatistics and one of the lead investigators at University of Miami.

“This isn’t just a matter of attitude—it’s about access. If a provider doubts treatment efficacy or holds stigmatizing beliefs, they’re less likely to screen or refer a patient. That becomes a system failure.”

The study also highlighted key institutional barriers that may reinforce stigma, including:

Time constraints
Lack of training
Limited referral resources
Discomfort discussing SUD with patients
Legal concerns
Minimal privacy in clinical settings

Senior author Lisa R. Metsch, professor of Sociomedical Sciences at Columbia Mailman School and Dean of the School of General Studies at Columbia University added, “We heard over and over that providers feel unequipped or unsupported to treat SUD—despite being on the frontlines. That’s especially true in primary care settings, where time pressures and limited resources are a daily challenge.” Metsch also added, “Notably, the majority of health providers agreed that insurance plans should cover patients with SUD at the same degree as they cover patients with other health conditions.”

Dentists, although typically less involved in treating SUD, are well-positioned to recognize oral signs of substance use and refer patients to appropriate care—but they, too, face gaps in training and systemic support.

“Going forward, we should strive to be more cognizant of the many treatment and provider roles we have distinguished in this study. By unpacking all the variations, we can start to build smarter interventions—tailored by specialty, setting, and substance,” said Parish.

Other co-authors are Viviana E. Horigian, University of Miami Miller School of Medicine; Harold A. Pollack, University of Chicago School of Social Work; Xiaoming Wang and Petra Jacobs, National Institute of Drug Abuse; Christina Drymon and Elizabeth Allen, National Opinion Research Center; Carlos del Rio, Emory University School of Medicine; and Margaret R. Pereyra and Lauren Gooden, Columbia Mailman School.

The study was supported by the National Institute on Drug Abuse Treatment Clinical Trials Network, grant 5UG1DA013720-23.

Columbia University Mailman School of Public Health

Founded in 1922, the Columbia University Mailman School of Public Health pursues an agenda of research, education, and service to address the critical and complex public health issues affecting New Yorkers, the nation and the world. The Columbia Mailman School is the third largest recipient of NIH grants among schools of public health. Its nearly 300 multi-disciplinary faculty members work in more than 100 countries around the world, addressing such issues as preventing infectious and chronic diseases, environmental health, maternal and child health, health policy, climate change and health, and public health preparedness. It is a leader in public health education with more than 1,300 graduate students from 55 nations pursuing a variety of master’s and doctoral degree programs. The Columbia Mailman School is also home to numerous world-renowned research centers, including ICAP and the Center for Infection and Immunity. For more information, please visit www.mailman.columbia.edu.

Journal

Addiction

DOI

10.1111/add.70122

Article Title

Healthcare provider stigma toward patients with substance use disorders

Breakthrough engineered enzyme for recycling of PET bottle and blended fibers at moderate temperatures

National Institutes of Natural Sciences

image:
Engineered PET2 Enzyme for Recycling of PET Bottle and Blended Fibers at Moderate Temperatures
view more
Credit: Akihiko Nakamura

Summary

Addressing the global plastic waste crisis, particularly hard-to-recycle blended PET fibers, demands environmentally friendlier recycling methods.
Researchers engineered a novel PET hydrolase PET2-21M and established large-scale production in yeast. This enzyme dramatically boosted PET bottle-grade PET breakdown.
In parallel, its direct precursor PET2-14M-6Hot successfully degraded challenging blended fibers (PET/cotton, PET/PU) at moderate temperatures.
This breakthrough offers a promising, energy-efficient path for a circular plastics economy, accelerating industrial-scale recycling of diverse polymer wastes.

A research team led by Professor Akihiko Nakamura of the Research Institute of Green Science and Technology, Shizuoka University (also a cross-appointment professor at the Institute for Molecular Science until March 2025), in collaboration with Researchers Takashi Matsuzaki and Toshiyuki Saeki of Kirin Holdings Co., Ltd., Professor Ryota Iino of the Institute for Molecular Science, and Professor Nobuyasu Koga of the Institute for Protein Research, The University of Osaka, have successfully engineered a novel PET hydrolase enzyme, PET2-21M, achieving a remarkable improvement in the biodegradation of bottle-grade polyethylene terephthalate (PET) plastics. High activity toward PET/cotton and PET/polyurethane (PU) textile blends was also demonstrated separately with the closely related variant PET2-14M-6Hot. This significant breakthrough addresses the urgent global challenge of recycling PET waste by offering a sustainable and efficient alternative to conventional recycling processes.

PET is a widely utilized synthetic polymer prominent in bottles, textiles, and packaging materials, representing approximately 83% of the synthetic fiber market. Despite its intrinsic recyclability, traditional mechanical recycling methods frequently result in material quality degradation and exhibit limited effectiveness for complex blended materials such as PET/cotton and PET/PU. Chemical recycling, while capable of producing high-purity materials, typically demands harsh conditions and environmentally hazardous reagents, thus limiting its practical sustainability.

In response, enzymatic recycling has emerged as an attractive alternative due to its capability to depolymerize PET into its original monomeric constituents under milder aqueous conditions. To enhance the PET-degrading efficiency of the enzyme PET2, researchers adopted an extensive engineering strategy. They systematically employed both random and targeted mutagenesis, combining seven newly identified beneficial mutations with a previously-reported engineered variant PET2-7M, resulting in the highly active PET2-14M enzyme. Additional surface modifications, which introduced positive charges to improve substrate binding, and strategic alterations in the substrate-binding cleft based on another enzyme HotPETase as a structural template, led to the creation of PET2-14M-6Hot. Further optimization produced the final engineered variant PET2-21M. Furthermore, large-scale productions of the PET2-14M-6Hot and PET2-21M were achieved in the yeast host, Komagataella phaffii. Notably, PET2-14M-6Hot reached yields of up to 691 mg L⁻¹ after 137 hours of cultivation, demonstrating high expression efficiency without glycosylation-induced heterogeneity.

The PET2-21M demonstrated significantly enhanced catalytic activity compared to the original enzyme wild-type PET2, with initial small-scale assays revealing a total product yield approximately 28.6 times greater. Subsequent scaled-up experiments in 300 mL reactors further validated these improvements; notably, PET2-21M depolymerized approximately 95% of commercial bottle-grade PET powder (20 g L⁻¹) within 24 hours at 60 °C, while the benchmark enzyme LCC-ICCG required its optimal temperature of 72 °C to reach a comparable conversion of 91%.

The superiority of PET2-21M was particularly evident under reduced enzyme loading conditions. Even when enzyme concentration was halved to 2.5 mg L⁻¹, PET2-21M maintained around 50% degradation efficiency, nearly doubling the performance of LCC-ICCG, which achieved only 26% conversion under identical conditions. This highlights PET2-21M’s substantial potential to lower catalytic requirements and associated costs.

Importantly, PET2-21M retained its competitive advantage under higher substrate loading conditions (40 g L⁻¹). At an enzyme dosage of 10 mg L⁻¹, PET2-21M achieved a 79% conversion at 60 °C, closely rivaling LCC-ICCG’s 95% conversion at its higher optimal temperature (72 °C). Furthermore, upon reducing enzyme dosage to 5 mg L⁻¹, PET2-21M still outperformed LCC-ICCG, demonstrating a 44% conversion compared to 29% for LCC-ICCG. This robust performance at moderate temperatures and reduced enzyme-to-substrate ratios positions PET2-21M as a highly promising candidate for industrial PET recycling processes, potentially enabling substantial reductions in both energy consumption and catalyst expenditure.

To evaluate the recycling potential of engineered PET hydrolases for textile waste, the PET2-14M-6Hot was compared with the benchmark enzyme LCC-ICCG on pure PET fibers and textile blends. At 60 °C, PET2-14M-6Hot generated 75.7 mM total degradation products from pure PET fibers within 24 hours, representing a 1.4-fold improvement over LCC-ICCG tested at its optimal 70 °C. Similarly, PET2-14M-6Hot achieved higher catalytic efficiency on PET/cotton (65/35 wt%) blends, producing 62.8 mM products versus 46.7 mM by LCC-ICCG, with minimal interference from cotton fibers.

For the challenging PET/PU textile blends (85/15 wt%), both enzymes exhibited reduced activity above PU’s glass-transition temperature (Tg ≈ 55 °C). Nevertheless, at a lower reaction temperature of 50 °C, PET2-14M-6Hot maintained substantial catalytic activity, yielding 19.2 mM degradation products—more than double the 8.2 mM obtained by LCC-ICCG under identical conditions. This underscores PET2-14M-6Hot’s superior capacity for processing complex blended textiles, which have traditionally resisted enzymatic degradation.

These results confirm the engineered PET2 enzyme family's significant potential for industrial-scale enzymatic recycling. Their ability to efficiently degrade diverse PET waste streams, including challenging textile blends at moderate temperatures, strongly supports broader applicability and sustainability benefits in PET recycling processes.

These findings represent a substantial advance towards realizing a more sustainable and economically viable circular plastics economy. The engineered PET2 enzymes’ superior ability to depolymerize PET and complex fiber blends at moderate temperatures holds significant promise for practical industrial recycling operations, particularly in handling difficult-to-process blended textile waste. Future research efforts target further optimization of enzyme efficiency at even lower reaction temperatures and in the blended materials, ultimately facilitating broader industrial adoption and minimizing the environmental footprint of global plastic recycling efforts.

Information of the paper

Authors: Takashi Matsuzaki, Toshiyuki Saeki, Fuhito Yamazaki, Natsuka Koyama, Tatsunori Okubo, Daiki Hombe, Yui Ogura, Yoshihito Hashino, Rie Tatsumi-Koga, Nobuyasu Koga, Ryota Iino, Akihiko Nakamura
Journal Name: ACS Sustainable Chemistry & Engineering
Journal Title: "Development and Production of Moderate-Thermophilic PET Hydrolase for PET Bottle and Fiber Recycling"
DOI: 10.1021/acssuschemeng.5c01602

Journal

ACS Sustainable Chemistry & Engineering

DOI

10.1021/acssuschemeng.5c01602

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Development and Production of Moderate-Thermophilic PET Hydrolase for PET Bottle and Fiber Recycling