Chinese researchers achieve major breakthrough in truly sustainable ‘DNA plastic’

By Joseph Maina

December 7, 2021

Researchers in China have unveiled a breakthrough that could provide a more sustainable and energy-efficient alternative to plastics — with none of their toxic effects.

The new bioplastic product, colloquially termed “DNA plastic,” is made from natural DNA and biomass-derived ionomers. Salmon sperm DNA is among the principal materials used in the formulation.

“To the best of our knowledge, our reported DNA plastics are the most environmentally sustainable materials of any other known plastics,” state the researchers in their report, published in the Journal of the American Chemical Society. “For the long run, developing sustainable bio-based plastics will be a satisfactory choice to reduce the dependency on nonrenewable petrochemicals and follow the principles of green chemistry and engineering in service of a sustainable society.”

The researchers are upbeat that their invention could well satiate the enormous global demand for plastics, banking on the sheer availability of the base material. As a raw material, DNA is copiously available for prolonged and sustainable production of bioplastics and it can be extracted from any organism, including plants, animals and microorganisms.

The study authors assert that the DNA plastics are compatible with the environment in that all raw materials are derived from bio-renewable resources and processing approaches are environmentally friendly, without involving high-energy consumption. The researchers cite a freeze-drying method that transformed DNA gels into sustainable DNA plastics, a relatively low-energy-consumption process compared with the melt processing method associated with conventional plastic manufacturing.

They also note that recyclable and nondestructive use is achieved to significantly prolong the service lifetime of bio-plastics, and that the disposal of waste bio-plastics follows two green routes, namely the recycling of waste plastics and enzyme-triggered controllable degradation.

Despite their widespread and important applications in everyday use, plastics, technically known as polymers, continue to raise fundamental concerns over their impact on the environment.

“Every year around 51−88 million tons of waste plastics accumulate in the environment globally, and the accumulation quantity is increasing at an alarming rate year by year. Current disposal methods, including landfilling (79 percent) and incineration (12 percent), lead to serious pollution of the agricultural environment and produce toxic substances that deplete the ozone layer,” note the researchers.

The environmental impact of plastics spans the entire cycle, from production and use to end-of-life. One option fronted to mitigate the adverse impacts of plastics on the environment is the development of materials that are compatible with the environment throughout their life cycle.

Researchers have previously attempted to develop bioplastics from bio-derived raw materials such as cellulose, starch and plant oil, but the resultant bioplastics failed to uphold the principles of green chemistry and engineering in their production, use and end-of-life options. Among the flaws cited include the high temperatures needed in their production, as well as challenges in recycling and reuse of the materials in a green and low-energy consumption context.

“We expect that if DNA is developed into bioplastics, the increasing demand of plastics that has reached 348 million metric tons/year will be effectively relieved in theory,” the researchers note.

Among their merits over petrochemical plastics, the DNA plastics showed good folding recoverability even at low temperatures, a property that offers great potential for applications in electronic skins and soft robots under extreme cold weather conditions.

The potential for controllable degradation is another plus for DNA plastics.

DNA plastics were also shown to be specifically and rapidly degraded in a controllable fashion when exposed to DNA digesting enzymes. This is unlike other bioplastics, which required multiple bio-enzymes to achieve complete degradation in a period spanning months to years.

DNA plastics also exhibited superior dimensional stability over a longer time period and demonstrated superior stability in polar solvents such as ethanol, while petrochemicals were seen to be unstable and could dissolve in organic solvents.

Further, CO2 emissions per functional unit of DNA plastic were markedly lower compared to polystyrene and polylactic acid, averaging 3 percent and 35 percent, respectively.

Although mass production of DNA plastics could pose a challenge, the researchers propose several ways to achieve industrial-scale production. These include derivatives from fruit production, microbial residues during antibiotic production in the biopharmaceutical industry, dry yeast from the bioethanol industry and algae.

While extoling the comparative merits of DNA plastics, the researchers recognize the anticipated challenges of the product in real-world settings. These include the compromised water-tolerant stability of DNA plastics, which limits their use in some application scenarios, and the mechanical strength, which has been balanced with the need for sustainability, among other considerations. They also cite the long-time stability of DNA plastics under UV radiation as an area for possible improvement.

Image: Close-up of pieces of bioplastic. Photo: Shutterstock/Cholpan