We may soon be finishing off a box of cereal and then eating the bag it came in. Researchers have turned to bacteria-produced cellulose to create a composite packaging material to replace plastic. The material is not only robust and sustainable to produce, but it’s also biodegradable and, what’s more, edible.
Plastics can take anywhere from 50 to 200 years to decompose, depending on what they’re made from. The use of petroleum-based plastics in packaging has led to significant pollution over the decades, leading to a push to develop more environmentally friendly and sustainable packaging materials.
Bio-derived polymers offer a way of ‘greening up’ single-use packaging. One in particular, bacterial cellulose (BC), has been of particular interest to researchers. An ultra-fine network of cellulose nanofibers synthesized by bacteria, BC has better properties than plant cellulose in its higher water-holding capacity, higher tensile strength, distinctly soft texture and high fiber content.
Now, researchers at the Chinese University of Hong Kong have used BC to create a new composite single-use packaging material that is not only environmentally friendly, but it’s also edible.
“Extensive research has been conducted on BC, including its use in intelligent packaging, smart films, and functionalized materials created through blending, coating, and other techniques,” said To Ngai, corresponding author of the study. “These studies demonstrate the potential of BC as a replacement for single-use plastic packaging materials, making it a logical starting point for our research.”
As the basis for the material, the researchers used cellulose secreted by the bacterium Komagataeibacter xylinus, a well-known producer of sustainable, non-toxic BC. Unlike plant cellulose, BC is produced by a process of fermentation, meaning that no trees or crops need to be harvested and no habitats destroyed. Incidentally, Komagataeibacter bacteria is often fermented to make the traditional tea beverage kombucha.
The researchers then embedded soy protein isolated from soybeans into the cellulose structure and coated it with an oil-resistant composite made from calcium alginate. All in all, they say, a relatively simple process.
“It does not require specific reaction conditions like chemical reactions, but rather a simple and practical method with mixing and coating,” said Ngai.
On testing, they found that the novel material was transparent, oil-resistant, non-toxic to human cells, and completely biodegraded in one to two months. They found that, compared to low-density polyethylene plastic, the material performed comparably as a single-use bag to house snacks, candy, street food, bread, or similar foods. Straws made from the material were strong enough to pierce the plastic membrane of a commercially available bubble tea and maintained their integrity after being soaked in water for 24 hours.
“This approach offers a promising solution to the challenge of developing sustainable and environmentally friendly packaging that can replace single-use plastics on a large scale,” said Ngai.
And, to top it off, the material’s components mean that it’s safe for humans and animals to eat.
“The material developed in this research is completely edible, making it safe for turtles and other sea animals to consume without causing aquatic toxicity in the ocean,” Ngai said.
The researchers plan to continue working on their novel packaging material, enhancing its versatility and addressing one of the downsides of using BC, its thermoplasticity or ability to be molded at elevated temperatures and then solidify when it cools.
“One of the main challenges with bacterial cellulose is that they are not thermoplastic, which limits their potential for use in certain applications,” Ngai said. “By addressing this issue, we hope to make bacterial cellulose films more competitive with traditional plastics while maintaining their eco-friendliness. This research serves as a reminder that natural raw materials already possess the necessary characteristics to perform beyond the functions of plastic packaging.”
The study was published in the journal Society of Chemical Industry.