Tag Archives: bioplastic

Low-cost carbon sequestration and eco-friendly manufacturing for chemicals with nanobio hybrid organisms

Years ago I was asked about carbon sequestration and nanotechnology and could not come up with any examples. At last I have something for the next time the question is asked. From a June 11, 2019 news item on ScienceDaily,

University of Colorado Boulder researchers have developed nanobio-hybrid organisms capable of using airborne carbon dioxide and nitrogen to produce a variety of plastics and fuels, a promising first step toward low-cost carbon sequestration and eco-friendly manufacturing for chemicals.

By using light-activated quantum dots to fire particular enzymes within microbial cells, the researchers were able to create “living factories” that eat harmful CO2 and convert it into useful products such as biodegradable plastic, gasoline, ammonia and biodiesel.

A June 11, 2019 University of Colorado at Boulder news release (also on EurekAlert) by Trent Knoss, which originated the news item, provides a deeper dive into the research,

“The innovation is a testament to the power of biochemical processes,” said Prashant Nagpal, lead author of the research and an assistant professor in CU Boulder’s Department of Chemical and Biological Engineering. “We’re looking at a technique that could improve CO2 capture to combat climate change and one day even potentially replace carbon-intensive manufacturing for plastics and fuels.”

The project began in 2013, when Nagpal and his colleagues began exploring the broad potential of nanoscopic quantum dots, which are tiny semiconductors similar to those used in television sets. Quantum dots can be injected into cells passively and are designed to attach and self-assemble to desired enzymes and then activate these enzymes on command using specific wavelengths of light.

Nagpal wanted to see if quantum dots could act as a spark plug to fire particular enzymes within microbial cells that have the means to convert airborne CO2 and nitrogen, but do not do so naturally due to a lack of photosynthesis.

By diffusing the specially-tailored dots into the cells of common microbial species found in soil, Nagpal and his colleagues bridged the gap. Now, exposure to even small amounts of indirect sunlight would activate the microbes’ CO2 appetite, without a need for any source of energy or food to carry out the energy-intensive biochemical conversions.

“Each cell is making millions of these chemicals and we showed they could exceed their natural yield by close to 200 percent,” Nagpal said.

The microbes, which lie dormant in water, release their resulting product to the surface, where it can be skimmed off and harvested for manufacturing. Different combinations of dots and light produce different products: Green wavelengths cause the bacteria to consume nitrogen and produce ammonia while redder wavelengths make the microbes feast on CO2 to produce plastic instead.

The process also shows promising signs of being able to operate at scale. The study found that even when the microbial factories were activated consistently for hours at a time, they showed few signs of exhaustion or depletion, indicating that the cells can regenerate and thus limit the need for rotation.

“We were very surprised that it worked as elegantly as it did,” Nagpal said. “We’re just getting started with the synthetic applications.”

The ideal futuristic scenario, Nagpal said, would be to have single-family homes and businesses pipe their CO2 emissions directly to a nearby holding pond, where microbes would convert them to a bioplastic. The owners would be able to sell the resulting product for a small profit while essentially offsetting their own carbon footprint.

“Even if the margins are low and it can’t compete with petrochemicals on a pure cost basis, there is still societal benefit to doing this,” Nagpal said. “If we could convert even a small fraction of local ditch ponds, it would have a sizeable impact on the carbon output of towns. It wouldn’t be asking much for people to implement. Many already make beer at home, for example, and this is no more complicated.”

The focus now, he said, will shift to optimizing the conversion process and bringing on new undergraduate students. Nagpal is looking to convert the project into an undergraduate lab experiment in the fall semester, funded by a CU Boulder Engineering Excellence Fund grant. Nagpal credits his current students with sticking with the project over the course of many years.

“It has been a long journey and their work has been invaluable,” he said. “I think these results show that it was worth it.”

Here’s a link to and a citation for the paper,

Nanorg Microbial Factories: Light-Driven Renewable Biochemical Synthesis Using Quantum Dot-Bacteria Nanobiohybrids by Yuchen Ding, John R. Bertram, Carrie Eckert, Rajesh Reddy Bommareddy, Rajan Patel, Alex Conradie, Samantha Bryan, Prashant Nagpal. J. Am. Chem. Soc.2019XXXXXXXXXX-XXX DOI: https://doi.org/10.1021/jacs.9b02549 Publication Date:June 7, 2019
Copyright © 2019 American Chemical Society

This paper is behind a paywall.

Eggshell-based bioplastics

Adding eggshell nanoparticles to a bioplastic (shown above) increases the strength and flexibility of the material, potentially making it more attractive for use in the packaging industry. Credit: Vijaya Rangari/Tuskegee University

Adding eggshell nanoparticles to a bioplastic (shown above) increases the strength and flexibility of the material, potentially making it more attractive for use in the packaging industry. Credit: Vijaya Rangari/Tuskegee University

A March 15, 2016 news item on Nanowerk describes the research,

Eggshells are both marvels and afterthoughts. Placed on end, they are as strong as the arches supporting ancient Roman aqueducts. Yet they readily crack in the middle, and once that happens, we discard them without a second thought. But now scientists report that adding tiny shards of eggshell to bioplastic could create a first-of-its-kind biodegradable packaging material that bends but does not easily break.

The researchers present their work today [March 15, 2016] at the 251st National Meeting & Exposition of the American Chemical Society (ACS).

A March 15, 2016 ACS news release (also on EurekAlert), which originated the news item, describes the work further,

“We’re breaking eggshells down into their most minute components and then infusing them into a special blend of bioplastics that we have developed,” says Vijaya K. Rangari, Ph.D. “These nano-sized eggshell particles add strength to the material and make them far more flexible than other bioplastics on the market. We believe that these traits — along with its biodegradability in the soil — could make this eggshell bioplastic a very attractive alternative packaging material.”

Worldwide, manufacturers produce about 300 million tons of plastic annually. Almost 99 percent of it is made with crude oil and other fossil fuels. Once it is discarded, petroleum-based plastics can last for centuries without breaking down. If burned, these plastics release carbon dioxide into the atmosphere, which can contribute to global climate change.

As an alternative, some manufacturers are producing bioplastics — a form of plastic derived from cornstarch, sweet potatoes or other renewable plant-based sources — that readily decompose or biodegrade once they are in the ground. However, most of these materials lack the strength and flexibility needed to work well in the packaging industry. And that’s a problem since the vast majority of plastic is used to hold, wrap and encase products. So petroleum-based materials continue to dominate the market, particularly in grocery and other retail stores, where estimates suggest that up to a trillion plastic bags are distributed worldwide every year.

To find a solution, Rangari, graduate student Boniface Tiimob and colleagues at Tuskegee University experimented with various plastic polymers. Eventually, they latched onto a mixture of 70 percent polybutyrate adipate terephthalate (PBAT), a petroleum polymer, and 30 percent polylactic acid (PLA), a polymer derived from cornstarch. PBAT, unlike other oil-based plastic polymers, is designed to begin degrading as soon as three months after it is put into the soil.

This mixture had many of the traits that the researchers were looking for, but they wanted to further enhance the flexibility of the material. So they created nanoparticles made of eggshells. They chose eggshells, in part, because they are porous, lightweight and mainly composed of calcium carbonate, a natural compound that easily decays.

The shells were washed, ground up in polypropylene glycol and then exposed to ultrasonic waves that broke the shell fragments down into nanoparticles more than 350,000 times smaller than the diameter of a human hair. Then, in a laboratory study, they infused a small fraction of these particles, each shaped like a deck of cards, into the 70/30 mixture of PBAT and PLA. The researchers found that this addition made the mixture 700 percent more flexible than other bioplastic blends. They say this pliability could make it ideal for use in retail packaging, grocery bags and food containers — including egg cartons.

In addition to bioplastics, Rangari’s team is investigating using eggshell nanoparticles to enhance wound healing, bone regeneration and drug delivery.