The researchers provided a comparison of various technologies for closed-loop recycling, which allow for the reuse of plastic through mechanical or chemical processing, eliminating the need for fossil-fuel-derived virgin materials. They considered technical metrics such as material quality and retention, as well as environmental metrics including energy use and greenhouse gas emissions.

“We know cost is one of the primary — if not the primary — drivers for recycling for companies wanting to invest in it,” said Taylor Uekert, lead author of “Technical, economic, and environmental comparison of closed-loop recycling technologies for common plastics,” which appears in the journal ACS Sustainable Chemistry & Engineering. “But I think it’s just so important to remember that there are other things that are equally important for our life on this planet, and we need to be considering those environmental impacts as well.”

Her co-authors, all from NREL, are Avantika Singh, Jason DesVeaux, Tapajyoti Ghosh, Arpit Bhatt, Geetanjali Yadav, Shaik Afzal, Julien Walzberg, Katrina Knauer, Scott Nicholson, Gregg Beckham, and Alberta Carpenter.

The article outlines how effectively closed-loop recycling technologies would work on polyethylene terephthalate (PET) and three types of polyolefins: high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP). These plastics have many uses. PET, for instance, is used to make bottles, trays, and carpets. HDPE is found in milk jugs, bags, containers, and toys. LDPE is commonly used to manufacture squeezable bottles, lids, and bags. PP, meanwhile, is used to make yogurt tubs, hangers, and straws.

The recycling rates of these polymers varied in the United States during 2019, from 2% for LDPE to 15% for PET bottles and containers.

“PET is like your common single-use water bottle,” Uekert said. “You might recycle that. But most likely it’s not going to come out the other end as a bottle. It’s going to come out as a plastic tray for putting food on or it might be converted to plastic fibers that could be used for clothing. It’s going back into the same type of plastic, but not necessarily the exact same type of plastic product.”

Two closed-loop recycling methods are available for HDPE, LDPE, and PP plastics: mechanical, in which the plastic is ground up, melted, and made into something new; and solvent-based dissolution, which removes impurities so that the plastic is of suitable quality for reuse. Those same processes can be used on PET in addition to three chemical recycling technologies: enzymatic hydrolysis, glycolysis, and methanolysis.

More than 400 million metric tons of plastic waste is generated globally each year. Current recycling strategies can capture a fraction of these plastics, but there is a lack of consistent data on the capabilities and impacts of these processes. The NREL study quantitatively characterized the performance of plastic recycling technologies — including factors that are usually only discussed qualitatively, like contamination tolerance — and established a methodology for comparing new recycling processes as they emerge.

“It’s not just that you can recycle plastic,” Uekert said. “It’s how effectively can you recycle that plastic?”

Although mechanical recycling outperforms all other technologies as well as virgin plastic production across economic and environmental metrics, the process yields lower quality plastic. Increasing the quality and quantity of plastics to be recycled through better sorting and pretreatment could improve the viability of mechanical recycling, the researchers said.

“To really enable a circular system where we keep as much material in the economy as possible, that’s when we really need to improve our [material] retention through things like better sorting and better yields of your recycling processes,” Uekert said. “If you have a process that only has a 75% yield, you’re going to end up needing slightly more electricity, slightly more chemicals, to recycle one kilogram of plastic than you would if you had something like a 90% or higher yield. That means your overall environmental impacts, your overall cost, is going to decrease as you increase your material retention.”

The researchers pointed out recycling should be treated as a decarbonization opportunity, with the technologies using electricity that could be generated from renewable sources.

Funding came from the U.S. Department of Energy’s Bioenergy Technologies Office and Advanced Materials and Manufacturing Technologies Office as part of the BOTTLE Consortium, a collaborative effort that stands for Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment.

NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for DOE by the Alliance for Sustainable Energy LLC.

It’s estimated that more than 90% of Americans are not meeting the recommended daily intake of choline. The current research, conducted in mice, suggests that dietary choline deficiency can have profound negative effects on the heart, liver and other organs.

Lack of adequate choline is also linked with profound changes in the brain associated with Alzheimer’s disease. These include pathologies implicated in the development of two classic hallmarks of the illness, amyloid plaques, which aggregate in the intercellular spaces between neurons, and tau tangles, which condense within the bodies of neurons.

The new research, led by scientists at Arizona State University, describes pathologies in normal mice deprived of dietary choline as well as choline deficient transgenic mice, which already exhibit symptoms associated with the disease. In both cases, dietary choline deficiency results in liver damage, enlargement of the heart and neurologic alterations in the AD mice typically accompanying Alzheimer’s disease, including increased levels of plaque-forming amyloid-beta protein and disease-linked alterations in tau protein.

Further, the study illustrates that choline deficiency in mice causes significant weight gain, and alterations in glucose metabolism, (which are tied to conditions such as diabetes), and deficits in motor skills.

In the case of humans, “it’s a twofold problem,” according to Ramon Velazquez, senior author of the study and Assistant professor with the ASU-Banner Neurodegenerative Disease Research Center. “First, people don’t reach the adequate daily intake of choline established by the Institute of Medicine in 1998. And secondly, there is vast literature showing that the recommended daily intake amounts are not optimal for brain-related functions.”

Ramon Velazquez led the new study on the importance of dietary choline for the brain and other organs. He is a researcher in the ASU-Banner Neurodegereative Disease Research Center.

The research highlights a constellation of physical and neurological changes linked to choline deficiency. Sufficient choline in the diet reduces levels of the amino acid homocysteine, which has been recognized as a neurotoxin contributing to neurodegeneration and is important for mediating functions such as learning and memory, through the production of acetylcholine.

The growing awareness of choline’s importance should encourage all adults to ensure proper choline intake. This is particularly true for those on plant-based diets, which may be low in naturally occurring choline, given that foods high in choline are eggs, meats, and poultry.

Plant-based, choline-rich foods, including soybeans, Brussel sprouts and toast can help boost choline in these cases. Further, inexpensive, over-the-counter choline supplements are encouraged to ensure system-wide health and guard the brain from the effects of neurodegeneration.

Brain-boosting nutrient

Choline is needed to produce acetylcholine, a neurotransmitter that plays an essential role in memory, muscle control and mood. Choline also builds cell membranes and helps regulate gene expression. The established recommendations set forth by the Institute of Medicine were based on evidence preventing fatty liver disease in men. New lines of evidence imply that the established recommended daily intake of dietary choline for adult women (425mg/day) and adult men (550mg/day) may not be optimal for proper brain health and cognition. Additionally, ~90% of Americans are not meeting the recommendation levels and may not even be aware that dietary choline is required on a daily basis.

Despite decades of research and billions of dollars invested since the discovery of the devastating ailment over a century ago, there remains no therapy capable of slowing the advance of the illness. Yet, new research findings suggest that environmental and lifestyle changes, including adequate choline, may help protect the brain from Alzheimer’s disease as well as improving overall health.

Velazquez is joined on the study by co-lead authors Nikhil Dave and Jessica Judd. The work is highly interdisciplinary, including researchers from the ASU Biosciences Mass spectrometry facility, and the Translational Cardiovascular Research Center at the University of Arizona College of Medicine in Phoenix, AZ.

“This collaborative work, spanning multiple institutions and surveying the molecular processes of aging at the systems level, adds to the body of evidence produced around the importance of dietary choline in healthy aging,” said Nikhil Dave.

“What I found particularly compelling about this project was that multiple organs, whose malfunction can have implications for brain health, were negatively impacted by a choline deficient diet,” said Jessica Judd.

The research appears in the current issue of the journal Aging Cell.

A prolific and mysterious killer

Alzheimer’s disease is the leading cause of dementia and the fifth leading cause of death among Americans aged 65 and older. Today, Alzheimer’s affects 6.5 million in the U.S. alone and is projected to strike close to 14 million Americans by 2060. By this time, the costs of managing Alzheimer’s are expected to exceed a $20 trillion, threatening the healthcare infrastructure while causing immense suffering.

The accumulation of sticky protein fragments outside neurons, (which form amyloid-beta plaques), and the buildup of an abnormal form of the protein tau within the bodies of neurons (tau tangles) have long been recognized signposts of Alzheimer’s disease. These brain alterations are typically followed by neurodegeneration, involving the damage and destruction of neurons. Plaques are believed to damage cell-to-cell communications in the brain while tangles block the transport of vital nutrients essential for proper cell function and survival.

In addition to amyloid-beta plaques and neurofibrillary tangles, the disease causes cell death in the brain and increasing cognitive impairment. The current work also found dysregulation of proteins in the hippocampus, a key structure affected in Alzheimer’s disease, tied to learning and memory. Both normal and AD mice showed dysregulated proteins in the hippocampus with a choline deficient diet, with the AD model showing severe effects.

Gathering storm

The recent, dramatic increase in Alzheimer’s disease incidence is of grave concern. Although deaths from stroke, heart disease and HIV decreased between 2000 and 2019, deaths from Alzheimer’s increased more than 145%. In addition to the toll on patients caused by the disease, Alzheimer’s has placed an immense burden on those caring for the sick. In 2021 alone, 16 billion hours of care were provided by over 11 million family members and other unpaid caregivers.

The first outward symptoms of the disease are usually related to language, memory, and thinking problems, as brain regions associated with these tasks tend to be among the first affected. Yet researchers now know that by the time the disease causes observable symptoms, it has been quietly ravaging the brain for 20 years or more.

Many factors contribute to the development of Alzheimer’s disease, from genetic predisposition to age, lifestyle and environmental influences. For reasons that remain murky, females face an increased risk of developing the disease.

Recent studies have identified diet as a significant factor associated with preventing cognitive decline. In earlier research, Velazquez and his colleagues demonstrated that when mice were fed a high choline diet, their offspring showed improvements in spatial memory, compared with a normal choline regimen in the womb. Intriguingly, the beneficial effects of choline supplementation are transgenerational, not only protecting mice receiving choline supplementation during gestation and lactation, but also the subsequent offspring of these mice, suggesting inherited modifications in their genes.

Subsequent studies in the Velazquez lab showed that choline administered to female mice throughout life yielded improvements in spatial memory, compared with those receiving a normal choline regimen.

Multifaceted effects

The new study examines mice at 3-12 months or early to late adulthood, (roughly equivalent to 20-60 years of age for humans). In the case of both normal and transgenic mice displaying symptoms of Alzheimer’s, those exposed to a deficient choline diet exhibited weight gain and adverse effects to their metabolism. Damage to the liver was observed through tissue analysis, as well as enlargement of the heart. Elevated soluble, oligomeric and insoluble amyloid-beta protein were detected as well as modifications to tau protein characteristic of those leading to neurofibrillary tangles in the brain.

Further, choline deficient mice performed poorly in a test of motor skills, when compared with mice receiving adequate choline in their diet. These adverse effects were heightened in the transgenic mice. Translating these findings to humans, this implies that people who are predisposed to Alzheimer’s disease or in the throes of the illness should ensure they are getting enough choline.

The study also involved a detailed exploration of proteins in the hippocampus, an area of the brain acutely affected by Alzheimer’s disease, as well as proteins detected in blood. Dietary choline deficiency altered important hippocampal networks. These pathologies include disruption of pathways associated with microtubule function and postsynaptic membrane regulation — both essential for proper brain function. In blood, proteins produced in the liver that play a role in metabolic function were particularly dysregulated with the choline deficient diet.

“Our work provides further support that dietary choline should be consumed on a daily basis given the need throughout the body,” Velazquez says.

Ultimately, controlled human clinical trials will be essential for establishing the effectiveness and appropriate dosages of choline, before encouraging lifelong choline supplementation. Nevertheless, the powerful new findings offer hope that choline may be one tool in the arsenal needed to defend the brain from neurodegeneration and age-related cognitive decline.

Investigators at Massachusetts General Hospital (MGH) recently developed an optimized method that improves the accuracy of inserting large DNA segments into a genome.

This approach could be used to insert a whole normal or “wild-type” replacement gene, which could act as a blanket therapy for a disease irrespective of a patient’s particular mutation.

The work involves the optimization of a new class of technologies called CRISPR-associated transposases (CASTs), which are promising tools for large DNA insertions that can be easily targeted to a desired genomic site via a reprogrammable guide RNA.

However, in their natural state, CASTs have undesirable properties for genome editing applications — namely, suboptimal product purity (how often only the intended DNA sequence is inserted into the genome) and a relatively high rate of unwanted off-target integration at unintended sites in the genome.

In their research published in Nature Biotechnology, a team led by first author Connor Tou, a graduate student at MIT and MGH, and senior author Ben Kleinstiver, PhD, an Assistant Investigator in the Center for Genomic Medicine at MGH and an Assistant Professor at Harvard Medical School, addressed these shortcomings by using protein engineering approaches to modify the properties of CAST systems.

They found that adding a certain enzyme called a nicking homing endonuclease to CASTs resulted in a dramatic increase in product purity towards the intended insertion.

Further optimization of CASTs’ structure led to DNA insertions with high integration efficiency at intended genomic targets with vastly reduced insertions at unwanted off-targets sites.

The researchers called the new and improved system “HELIX,” which is short for Homing Endonuclease-assisted Large-sequence Integrating CAST-compleX.

“We demonstrated a generalizable approach that can be used to modify a variety of CAST systems into safer and more effective versions that have high product purity and genome-wide specificity,” says Tou.

“By combining our insights, we created HELIX systems with greater than 96% on-target integration specificity — increased from approximately 50% for the naturally occurring wild-type CAST system. We also determined that HELIX maintains its advantageous properties in human cells.”

Kleinstiver notes that the technology could have applications beyond the ability to restore normal healthy genes to individuals with disease-causing mutations.

“Additionally, programmable DNA integration can facilitate cell engineering efforts where installation of large genetic sequences at targeted locations could endow cells with new capabilities while obviating safety, efficacy, and manufacturing issues resulting from traditional random integration approaches,” he says.

The study is also co-authored by Benno Orr.

This work was supported by the National Science Foundation and MGH.