A tangled web of sugar beets and plastic

A material made of long, tangled strands of cellulose — a major component of plant cell walls — shows promise as a reinforcement for biodegradable plant-based plastics. In 2022, a company in Japan began commercially producing this ‘bacterial nanocellulose’ using a microbial fermentation process.

Kusano Sakko, based in Japan’s agricultural heartland on the island of Hokkaido, launched the country’s first and only commercial-scale bacterial nanocellulose factory in collaboration with Hokkaido University in 2022. The endeavour aims to hasten the transition to biodegradable plastics, as well as save Hokkaido’s historic sugar beet industry.

Underwriting waste

Kusano Sakko’s bacterial nanocellulose, patented and sold as ‘Fibnano’, forms a white gel that is synthesized by fermenting sugar beet molasses, a byproduct of sugar production.

“Using our techniques, the cellulose strands become tangled and form a web that strengthens the materials they are added to,” explains Ryo Serizawa, one of the company’s researchers. Fibnano is already used as a thickening agent in foods, but specialized stirring and cell culturing techniques developed at Kusano Sakko have given it a new lease of life in reinforcing plant-derived plastics. “In contrast to other similar products, produced by shredding wood into smaller pieces to produce a pulp, our bacteria-derived cellulose fibres provide better reinforcement, since the cellulose strands remain quite long and thus become strongly webbed.”

Takatomo Kusano, the company’s president, adds that the cultivation of sugar beets supports other key crops in Hokkaido, because they help suppress the spread of plant diseases by supporting important microorganisms in the soil.

As in many parts of the world, farmers in Hokkaido cycle between different crops in the same fields including sugar beet, wheat, various beans and other vegetables. However, declining consumer demand for sugar, and consequently a drop in sugar beet production, has been a threat to this enduring agricultural industry.

“Bacterial nanocellulose production could be one way to revitalize sugar beet demand,” Kusano says.

Recyclable resin

Using Fibnano, Kusano Sakko and Kanazawa University also developed a plant-based plastic, called Fibnano Resin, which combines Fibnano with cellulose acetate, a common plant-derived, biodegradable plastic.

“Fibnano Resin’s strength, heat resistance, and ease of processing is comparable to common petroleum-based plastics. We expect to use it to produce eating utensils, containers, and automobile parts,” says Serizawa. “Fibnano Resin is also easier to recycle, since the length of the cellulose strands mean they can be shredded and remoulded without significantly reducing their webbing effect, and thus the plastic’s strength, too much. Many other major biodegradable plastics must be chemically broken down to the level of monomers to be recycled.”

Changes to the source of the cellulose acetate used in Fibnano Resin are also underway. “The main ingredient typically used to create cellulose acetate is wood or cotton. The goal is to replace these with sugar beet pulp,” explains Serizawa.

The production of Fibnano Resin would benefit Hokkaido by helping to maintain the sugar beet industry — but it may have much wider applications. Kusano says his company’s research could lead to the development of bioplastics from many different crops.

For example, banana plants are a potentially abundant source of long cellulose stands similar to those found in Fibnano, he says. “We hope to utilize byproducts from many local agricultural crops to help manufacture biodegradable plastics for local communities. Hokkaido is only the beginning.”